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<ul><li>Control of Endocrine Activity </li></ul><ul><li>The physiologic effects of hormones depend largely on their concen...
<ul><li>Control of Endocrine Activity </li></ul><ul><li>[Hormone] as seen by target cells is determined by 3 factors:   </...
Hormone Synthesis Diversity of hormones structures Lots of interesting pathways of biosynthesis Simplest of hormones-amino...
Hormone Synthesis Y also substrate for generation of thyroid hormones W is precursor for serotonin, a CNS NT and melatonin...
Hormone Synthesis Steroid Hormones Made within the SER Steroid secreting cells easily recognized  Complex multiple enzyme ...
Hormone Synthesis Thyroid Hormones Made on protienaceous substrates outside the cell Thyroglobulin Then taken up via endoc...
Hormone Synthesis Prohormones Result from cleavage events after translation Even have preprohormones Examples Renin (enzym...
Hormone Synthesis Prohormones Angiotensin II  and  bradykins  are examples of hormones that are released from liver cells ...
Hormone Synthesis NTs Made in axon end of neurons Neuropeptides like oxytocin and vasopressin also made in neurons
Hormone Synthesis Summary Variety of processes and intracellular locations involved SER, RER, Cholesterol from inside and ...
Control of Hormone Secretion Most hormones are made within cells are packaged in secretory vesicles until released -Except...
Control of Hormone Secretion Internal and external effectors Extrinsic-light, sounds, smell, temp,  Etc. Stimulation of ho...
Control of Hormone Secretion
Control of Hormone Secretion Hormones often stimulate secretion of hormones from other endocrine glands Pit hormones TSH, ...
Control of Hormone Secretion Neuroendocrine transduction stimulation of hormone secretion by nerves
Control of Hormone Secretion Hormone interaction with some membrane receptors results in membrane depolarization-stimulate...
Hormone Delivery Several routes of delivery 1.Endocrine 2. neurocrine- neuron contact target cell and releases hormone 3. ...
Hormone Circulation and metabolism Peptide hormones have short half lives Broken down by … Most steroid hormones bound to ...
<ul><li>Feedback Control of Hormone Production </li></ul><ul><li>Feedback circuits  </li></ul><ul><li>are at the root of m...
<ul><li>Feedback Control of Hormone Production </li></ul><ul><li>Negative feedback is seen when the output of a pathway in...
<ul><li>Feedback loops are used extensively to regulate secretion of hormones </li></ul><ul><li>An important negative feed...
<ul><li>The basic mechanisms for control in this system (illustrated on next slide) are:  </li></ul><ul><li>1.Neurons in t...
Inhibition of TRH secretion leads to shut-off of TSH secretion, which leads to shut-off of thyroid hormone secretion. As t...
Target cell response TRH receptors only found in anterior pituitary TSH receptors only found in thyroid gland TH receptors...
<ul><li>Another type of feedback is seen in endocrine systems that regulate concentrations of blood components such as glu...
<ul><li>Hormone Profiles: Concentrations Over Time </li></ul><ul><li>One important consequence of the feedback controls th...
<ul><li>The pulsatile nature of LH  secretion in this animal is evident.  </li></ul><ul><li>LH is secreted from the anteri...
<ul><li>A pulsatile pattern of secretion is seen for virtually all hormones, with variations in pulse characteristics that...
<ul><li>Mechanisms of Hormone Action </li></ul><ul><li>Immediately after discovery of a new hormone, a majority of effort ...
<ul><li>Mechanisms of Hormone Action </li></ul><ul><li>Understanding mechanism of action is itself a broad task, encompass...
Physiological roles of Hormones Hormones control of activity of all cells in the body Affect cellular synthesis and secret...
Physiological roles of Hormones Reproduction Cell growth and proliferation Excretion and reabsoroption of ions Affect acti...
Physiological roles of Hormones Some hormones only exist a few times in the life of an individual hCG Sometimes still have...
General mechanisms of Hormone action Receptors Second messengers Phosphorylation involves STY Kinases and phosphatases
Reminder about General mechanisms of Hormone action Steroid hormones have intracellular receptors.  So do Thyroid hormones
Endocrine pathophysiology Failure of a gland to secrete enough hormone can lead to fatal consequences No insulin-hyperglyc...
General mechanisms of hormone action Hormones regulate specific target tissues NOT ALL CELLS IN the body Determined by?? R...
Hormone response effected by  Receptor Levels  and  hormone levels Oxy and vasopressin AVP have similar structure and both...
Hormone response effected by  Receptor Levels  and  hormone levels When one hormone binds to the receptor of another hormo...
Some hormones stimulate a number of tissues. Insulin stimulates glucose uptake into  skeletal muscle and Fat cells But als...
Insulin receptors at high levels in  skeletal muscle  Fat cells LIVER  Cells where INSULIN MODULATES glucose metabolism
Insulin receptors at low levels in  all other tissues where this hormone only has a modest effect on GROWTH DOES NOT MODUL...
RECEPTORS FOR A PARTICULAR HORMONE ARE ONLY EXPRESSED IN CELLS WHERE THE HORMONE ACTS. MORE ACTION-MORE RECEPTORS UNDERSTA...
Hormone response effected by  Receptor Levels  and  hormone levels Have high levels of receptor in tissue that are primary...
Hormones act via own receptors at normal concentrations High hormone concentration can act on similar receptors NE and Epi...
In most cases, a maximum biological response to a hormone is achieved when only a small % of the receptors are occupied. W...
<ul><li>There are  4 classes of membrane bound receptors </li></ul><ul><li>Those that are enzymes (have tyrosine kinase ac...
Peptide hormones act via PM receptors There are 4 classes of membrane bound receptors 1. Those that are enzymes (have tyro...
<ul><li>There are  4 classes of membrane bound receptors </li></ul><ul><li>Those that are enzymes (have tyrosine kinase ac...
KIN ASE  activity X-OH  X-OP Phosphat ase  activity Amino acid substrates S T Y
<ul><li>There are  4 classes of membrane bound receptors </li></ul><ul><li>Those that are enzymes </li></ul><ul><li>Insuli...
2. Ion channels Ligand binding changes the conformation of the receptor so that specific ions flow through it; the resulta...
There are  4 classes of membrane bound receptors 3. Receptors coupled to G proteins (7TMDS) Odorant Receptors Adrenergic r...
 
 
 
 
 
 
 
 
7 hydrophobic membrane spanning domains Internal G protein interacting region N terminal glycosylation C-term phosphorylat...
Mediate signals for proteins, peptides, NT Odorants and photons
hydrophobic membrane spanning domains 22 -28 hydrophobic AA
Many of the receptors for peptide hormones and NTs are linked to G proteins
Most neuropeptide receptors
There are  4 classes of membrane bound receptors 4. Receptor that don’t have enzymatic activity (utilize the JAK STAT path...
The JAK/STAT Signaling Pathway
JAK STAT pathway   Ligand binds receptor Receptor Dimerizes Receptor associate with JAK kinase JAK phosphorylates receptor...
JAK STAT pathway   Used by Growth Hormone And prolactin And EPO Interferons
 
<ul><li>There are  4 classes of membrane bound receptors </li></ul><ul><li>Those that are enzymes (have tyrosine kinase ac...
 
Second Messengers of Hormone Action  Cyclic Nucleotides Generated by Nucleotide cyclyzing enzymes-located on inner surface...
 
cAMP and cGMP  Combine with cyclic dependent protein kinases  cAMP associates and activates cyclic dependent protein kinas...
Genomic actions of cAMP  Many second messengers, result in immediate response Others have actions which are blocked by act...
 
Enzyme phos. Leads to a cascade effect Results in amplification So little hormone or second messenger have a large effect ...
 
cAMP and cGMP rapidly metabolized Action of kinases Reversed by phosphatases When initiate a response, also initiate a mea...
cAMP and cGMP get Inactivated by phosphodiesterases (PDE) To 5’AMP or 5’ GMP  cyclase  Activity of PDEs inhibited by methy...
Many hormones use adenylate cyclase to cause a physiological response. Some activate this enzyme Others can inhibit
 
 
Receptor G-protein interactions mediate different signal transduction pathways PLC Adenylate cyclase PLA2 Ion Channel* *G ...
Some Second Messengers
<ul><li>Multiple Membrane Messengers  </li></ul><ul><li>PI (phosphoinosotides) are phospholipids in PM of all eukaryotes <...
 
 
Protein Kinase C (PKC) Multifunctional enzyme Many types Ca++ dependent and independent Inactive until associates with PM ...
 
Eicosanoids and Hormone Action Eicosanoids are produced by cells in response to some hormones Intracellular second messeng...
Eicosanoids and Hormone Action Common Eicosanoid PGE2 PGF2a Prostacylin (PGI2) PGI2 and PGE2 can activate adenylate cyclase
Eicosanoids are produced exclusively within the PM Primarily derived from AA that is release from phospholipids via action...
 
Prostacyclin (PGI 2 ) Produced by blood vessel wall Most potent natural inhibitor of blood platelet aggregation Activates ...
ThromboxaneA2 specific product of the platelets 2 types of prostaglandins  thromboxane (vasoconstrictor) and PGI2 (vasodil...
Leukotrienes Made by leukocytes Important in vascular contraction and permeability Lots of diseases associated with increa...
Many prostaglandins act as local mediators -paracrine and autocrine signaling  Destroyed near the site of their synthesis....
Not all hormones work via cell surface receptors  Steroid and Thyroid Hormone receptors Receptors are present in cytosol  ...
Hormones enter cell by diffusion (hydrophobic) Usually bind receptor in cytosol (displace a binding protein) Translocates ...
Hormone/receptor complex translocates to the nucleus and binds promoters at hormone response element EREs (estrogen respon...
The hormone and receptor complex directly bind response elements with the DNA
 
Can all Communicate with the nucleus
Hormones are complex Lots of things to be studied regarding hormones (see next slide) Methods are used to perform ENDOCRIN...
<ul><li>General considerations </li></ul><ul><li>Source </li></ul><ul><li>Structure determination * (inject or oral) </li>...
Histological and cytological studies Hypertrophic- enlarged  This means bigger cells Contain more ER and Golgi Opposite of...
 
 
Hypertrophic- enlarged  This means bigger cells Contain more ER and Golgi Opposite of  atrophic
Hyperplasia  or Hyperplastic An increase in number
Can have  Hypertrophy or Hyperplasia  or  both  depending on condition
 
Immunocytochemistry This is method to examine peptide or peptide hormone in a tissue. Must have an  antibody  against that...
Immunocytochemistry to show marker of Hodgkins lymphoma
 
Immunocytochemistry This is method CAN ALSO BE used to determine what tissue produces a hormone and/or where in the cell i...
 
Surgical Methods Endocrine organs can be transplanted to a new location Ectopic-abnormal site  Hypophysectomy-removal of p...
 
Ectopic-abnormal site
Removal of both members of paired (bilateral roans) such as adrenals or gonads usually leads to COMPLETE loss of dependent...
Parabiosis Animals are sutured together and share vascular systems Remove endocrine gland of one mouse, the organs of othe...
Obese gene -genetic defect in this gene causes obesity and type II diabetes The obesity gene codes for a hormone called  l...
diabetes gene -genetic defect in this gene causes obesity and type II diabetes The diabetes gene codes for the  leptin rec...
Ob/ob mice-no leptin  db/db-no leptin receptor 2 commonly used rodent models of type II diabetes
Parabiosis of ob/ob and db/db mice Ob/ob mice-no leptin db/db-no leptin receptor
Gray mouse is wild type Ob mouse and wild type-get leaner ob mouse. Sharing Hormone
db mouse and wild type-db does not get leaner because of defective receptor, not a problem with the hormone.
db mouse and ob mouse-ob mouse gets better as it gets circulating hormone from db mouse. Db mouse does not improve because...
This pivotal parabiosis experiment showed that  ob gene coded for circulating factor and that db did not .
 
Positional cloning  is method to identify and clone the gene that creates a phenotype.  So-finding the genotype
Positional cloning  is method to identify and clone the gene that creates a phenotype.  So-finding the genotype Obese mice...
 
Obese mice-defect in obese gene Found was fat specific
Chemicals Alloxan or streptozoticn destroy islets which produce insulin-induce Type I diabetes in an animal Cobalt chlorid...
Hormone Replacement Therapy (HRT) Reverse the undesirable effects of hormone loss following surgery or disease state or ag...
Immunological Neutralization of Hormone activity Antibodies against a hormone injected. Bind hormone and inhibit its actio...
Bioassays Different approaches to examine hormone activity Based on activity (enzymatic) Or association with another molec...
Bioassays Different approaches to examine hormone activity Structure-Activity Studies Site directed mutagenesis
Bioassays Different approaches to examine hormone activity Structure-Activity Studies Site directed mutagenesis
Structure-Activity Studies Mutate part of the gene or one base of the gene to determine if that part is important in hormo...
Radioisotope Studies I 125  take up by thyroid Radioactive Ca measured P to perform phosphorylation studies Half life stud...
Radioisotope Studies I 125  take up by thyroid
Chemical ID 1 0 - amino acid sequence  2 0 – secondary  3 0 –   4 0 – association with other proteins  Modifications like ...
RIA Detection of hormones at minute concentrations.  Need an antibody
RIA Detection of hormones at minute concentrations. Need an antibody
RIA Nobel Prize in Medicine (1977) to Rosalyn Yalow
Electrophysiology   membrane potential
Pharmacological experiments Actinomycin D-inhibits transcription Cycloheximide-inhibits translation Colchicine-disrupt mic...
Pharmacological experiments Actinomycin D and  Cycloheximide Can be used to determine if an action of a hormone is genomic
Specific Example To determine if effect of a hormone is dependent on new proteins synthesis, treat target cells with CH th...
Pharmacological experiments Colchicine and Cytochalasin can be used to tell if signaling or secretion is dependent on cyto...
Tissue Extracts and purification Type I diabetics need daily injections of insulin Used to come from pigs, cattle, horse. ...
Tissue Extracts and purification Disadvantage of using hormones purified from animals or   Slaughterhouse blood -Contamina...
Recombinant DNA methods Way in which we make insulin Genetic engineering in various species Fish, mice, rats.
Transgenic Animals  introduce gene in animal -Usually replace wild type with a mutant -Or express gene from a different pr...
 
Transgenic Mice over expressing Tropomodulin Have enlarged right atrium and ventricle and are larger
Labeled for two different proteins which are normally present in myofibrils. The alternating bands of tropomodulin (green)...
The normal alternating pattern of tropomodulin and alpha-actinin  immunoreactivity has been disturbed. The yellow color in...
transgenic mice that overexpress  TGFß1 in the CNS  animals developed severe hydrocephalus  transgenic colony serves as a ...
GH receptor knockout
GFP mice
overexpress neurotrophin-3 (NT-3) in skeletal muscle  When lifted by the tail, wildtype extend their hindlimbs and digits....
Transgenic mice has different coat color Transgenic mice extremely useful in studying diseases
Test is Feb 10 STUDY your NOTES  and the study guide
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Control of Endocrine Activity The physiologic effects of ...

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Control of Endocrine Activity The physiologic effects of ...

  1. 1. <ul><li>Control of Endocrine Activity </li></ul><ul><li>The physiologic effects of hormones depend largely on their concentration in blood and extracellular fluid. Almost inevitably, disease results when hormone concentrations are either too high or too low, and precise control over circulating concentrations of hormones is therefore crucial. The concentration of hormone as seen by target cells is determined by three factors: </li></ul><ul><li>1.Rate of production: </li></ul><ul><li>2.Rate of delivery </li></ul><ul><li>3.Rate of degradation and elimination: </li></ul>
  2. 2. <ul><li>Control of Endocrine Activity </li></ul><ul><li>[Hormone] as seen by target cells is determined by 3 factors: </li></ul><ul><li>Rate of production: Synthesis and secretion of hormones are the most highly regulated aspect of endocrine control. Such control is mediated by positive and negative feedback circuits . </li></ul><ul><li>Rate of delivery: An example of this effect is blood flow to a target organ or group of target cells - high blood flow delivers more hormone than low blood flow. </li></ul><ul><li>Rate of degradation and elimination: Hormones have characteristic rates of decay, and are metabolized and excreted from the body via several routes. Shutting off secretion of a hormone that has a very short halflife causes circulating hormone concentration to plummet, but if a hormone's biological halflife is long, effective concentrations persist for some time after secretion ceases. </li></ul>
  3. 3. Hormone Synthesis Diversity of hormones structures Lots of interesting pathways of biosynthesis Simplest of hormones-amino acids Glycine and glutamate -act as NTs in brain F and Y-are precursors of dopamine, NE and Epi Which also function as NTs
  4. 4. Hormone Synthesis Y also substrate for generation of thyroid hormones W is precursor for serotonin, a CNS NT and melatonin, a pineal hormone
  5. 5. Hormone Synthesis Steroid Hormones Made within the SER Steroid secreting cells easily recognized Complex multiple enzyme system for synthesis secretion
  6. 6. Hormone Synthesis Thyroid Hormones Made on protienaceous substrates outside the cell Thyroglobulin Then taken up via endocytosis into the thyroid gland-released from carrier protein prior to secretion from thyroid. UNIQUE PROCESS
  7. 7. Hormone Synthesis Prohormones Result from cleavage events after translation Even have preprohormones Examples Renin (enzyme from Kidney) Acts on angiotensinogen (substrate from liver) Results in ANGIOTENSIN I which is converted by another enzyme to Antgiotensin II
  8. 8. Hormone Synthesis Prohormones Angiotensin II and bradykins are examples of hormones that are released from liver cells as larger prohormones
  9. 9. Hormone Synthesis NTs Made in axon end of neurons Neuropeptides like oxytocin and vasopressin also made in neurons
  10. 10. Hormone Synthesis Summary Variety of processes and intracellular locations involved SER, RER, Cholesterol from inside and outside the cell, Secretory pathway involved in hormone modifications, particulary glycosylation
  11. 11. Control of Hormone Secretion Most hormones are made within cells are packaged in secretory vesicles until released -Except ….
  12. 12. Control of Hormone Secretion Internal and external effectors Extrinsic-light, sounds, smell, temp, Etc. Stimulation of hormone secreting cells results in vesicle fusion with the PM and exocytosis of secretory granules
  13. 13. Control of Hormone Secretion
  14. 14. Control of Hormone Secretion Hormones often stimulate secretion of hormones from other endocrine glands Pit hormones TSH, FSH, LH and ACTH simulate target tissue cells of thyroid, adrenal, gonads to secrete their own hormones Hormones control other hormones Cascade effect
  15. 15. Control of Hormone Secretion Neuroendocrine transduction stimulation of hormone secretion by nerves
  16. 16. Control of Hormone Secretion Hormone interaction with some membrane receptors results in membrane depolarization-stimulates movement of Ca++into cells which results in sec. vesicle exocytosis Some chemical messenger inhibit secretion by resulting ……
  17. 17. Hormone Delivery Several routes of delivery 1.Endocrine 2. neurocrine- neuron contact target cell and releases hormone 3. neuroendocrine-neuron to blood 4. Paracrine 5.lumonal-released into lumen of the gut 6. Autocrine Some delivered by all these routes
  18. 18. Hormone Circulation and metabolism Peptide hormones have short half lives Broken down by … Most steroid hormones bound to plasma proteins. Steroid hormones much more stable
  19. 19. <ul><li>Feedback Control of Hormone Production </li></ul><ul><li>Feedback circuits </li></ul><ul><li>are at the root of most control mechanisms in physiology, </li></ul><ul><li>and are particularly prominent in the endocrine system. </li></ul><ul><li>Instances of positive feedback certainly occur, but negative feedback is much more common. </li></ul>
  20. 20. <ul><li>Feedback Control of Hormone Production </li></ul><ul><li>Negative feedback is seen when the output of a pathway inhibits inputs to the pathway. </li></ul><ul><li>The heating system in your home is a simple negative feedback circuit. </li></ul>
  21. 21. <ul><li>Feedback loops are used extensively to regulate secretion of hormones </li></ul><ul><li>An important negative feedback loop is seen in control of thyroid hormone secretion. The thyroid hormones thyroxine and triiodothyronine (&quot;T4 and T3&quot;) are synthesized and secreted by thyroid glands and affect metabolism throughout the body. </li></ul>
  22. 22. <ul><li>The basic mechanisms for control in this system (illustrated on next slide) are: </li></ul><ul><li>1.Neurons in the hypothalamus secrete thyroid releasing hormone (TRH), which stimulates cells in the anterior pituitary to secrete thyroid-stimulating hormone (TSH). </li></ul><ul><li>2. TSH binds to receptors on epithelial cells in the thyroid gland, stimulating synthesis and secretion of thyroid hormones, which affect probably all cells in the body. </li></ul><ul><li>3.When blood concentrations of thyroid hormones increase above a certain threshold, TRH-secreting neurons in the hypothalamus are inhibited and stop secreting TRH. This is an example of &quot;negative feedback&quot;. </li></ul>
  23. 23. Inhibition of TRH secretion leads to shut-off of TSH secretion, which leads to shut-off of thyroid hormone secretion. As thyroid hormone levels decay below the threshold, negative feedback is relieved, TRH secretion starts again, leading to TSH secretion ... + + - -
  24. 24. Target cell response TRH receptors only found in anterior pituitary TSH receptors only found in thyroid gland TH receptors found on every cell Cascade effect + + - -
  25. 25. <ul><li>Another type of feedback is seen in endocrine systems that regulate concentrations of blood components such as glucose. </li></ul><ul><li>Drink a glass of milk or eat a candy bar and the following (simplified) series of events will occur: </li></ul><ul><li>Glucose from the ingested lactose or sucrose is absorbed in the intestine and the level of glucose in blood rises. </li></ul><ul><li>Elevation of blood glucose concentration stimulates endocrine cells in the pancreas to release insulin. </li></ul><ul><li>Insulin has the major effect of facilitating entry of glucose into many cells of the body - as a result, blood glucose levels fall. </li></ul><ul><li>When the level of blood glucose falls sufficiently, the stimulus for insulin release disappears and insulin is no longer secreted. </li></ul><ul><li>Numerous other examples of specific endocrine feedback circuits will be presented in the sections on specific hormones or endocrine organs. </li></ul>
  26. 26. <ul><li>Hormone Profiles: Concentrations Over Time </li></ul><ul><li>One important consequence of the feedback controls that govern hormone concentrations and the fact that hormones have a limited lifespan or half-life is that most hormones are secreted in &quot;pulses&quot;. The following graph depicts concentrations of LH in the blood of a female dog over a period of 8 hours, with samples collected every 15 minutes: </li></ul>
  27. 27. <ul><li>The pulsatile nature of LH secretion in this animal is evident. </li></ul><ul><li>LH is secreted from the anterior pituitary and critically involved in reproductive function; the frequency and amplitude of pulses are quite different at different stages of the reproductive cycle. </li></ul><ul><li>With reference to clinical endocrinology, examination of the graph should also demonstrate the caution necessary in interpreting endocrine data based on isolated samples. </li></ul><ul><li>- </li></ul>
  28. 28. <ul><li>A pulsatile pattern of secretion is seen for virtually all hormones, with variations in pulse characteristics that reflect specific physiologic states. </li></ul><ul><li>In addition to the short-term pulses discussed here, longer-term temporal oscillations or endocrine rhythms are also commonly observed and undoubtedly important in both normal and pathologic states. </li></ul>
  29. 29. <ul><li>Mechanisms of Hormone Action </li></ul><ul><li>Immediately after discovery of a new hormone, a majority of effort is devoted to delineating its sites of synthesis and target cells, and in characterizing the myriad of physiologic responses it invokes. An equally important area of study is to determine precisely how the hormone acts to change the physiologic state of its target cells - its mechanism of action . </li></ul>
  30. 30. <ul><li>Mechanisms of Hormone Action </li></ul><ul><li>Understanding mechanism of action is itself a broad task, encompassing structure and function of the receptor, how the bound receptor transduces a signal inside the cell and the end effectors of that signal. This information is not only of great interest to basic science, but critical to understanding and treating diseases of the endocrine system, and in using hormones as drugs. </li></ul>
  31. 31. Physiological roles of Hormones Hormones control of activity of all cells in the body Affect cellular synthesis and secretion of other hormones After metabolic processes (catabolic and anabolic). Turnover of sugar, proteins and fats Affect Contraction, relaxation and metabolism of Muscle
  32. 32. Physiological roles of Hormones Reproduction Cell growth and proliferation Excretion and reabsoroption of ions Affect action of other hormones Role in animal behavior
  33. 33. Physiological roles of Hormones Some hormones only exist a few times in the life of an individual hCG Sometimes still have hormone but not sensitive to it any longer Sometimes no longer produce hormone-thyroid hormone, estrogen
  34. 34. General mechanisms of Hormone action Receptors Second messengers Phosphorylation involves STY Kinases and phosphatases
  35. 35. Reminder about General mechanisms of Hormone action Steroid hormones have intracellular receptors. So do Thyroid hormones
  36. 36. Endocrine pathophysiology Failure of a gland to secrete enough hormone can lead to fatal consequences No insulin-hyperglycemia-coma and death if untreated
  37. 37. General mechanisms of hormone action Hormones regulate specific target tissues NOT ALL CELLS IN the body Determined by?? Receptors -proteins bind hormones Contribute to specificity of action Can be PM or cytosolic or nuclear
  38. 38. Hormone response effected by Receptor Levels and hormone levels Oxy and vasopressin AVP have similar structure and both hormones stimulate uterine smooth muscle contraction and activate renal cAMP Uterine receptors more sensitive to OXY Renal receptor more sensitive to AVP Normal hormone conc. Each hormone only activate appropriate cell type
  39. 39. Hormone response effected by Receptor Levels and hormone levels When one hormone binds to the receptor of another hormone, this is called CROSS TALK Happens with lots of hormones. If hormone levels are high, will not only act on its own receptor, but similar hormone receptors
  40. 40. Some hormones stimulate a number of tissues. Insulin stimulates glucose uptake into skeletal muscle and Fat cells But also talks to liver to shut down output of glucose from liver High Insulin receptor levels on fat, muscle and liver, but low levels in other tissues.
  41. 41. Insulin receptors at high levels in skeletal muscle Fat cells LIVER Cells where INSULIN MODULATES glucose metabolism
  42. 42. Insulin receptors at low levels in all other tissues where this hormone only has a modest effect on GROWTH DOES NOT MODULATE GLUCOSE METABOLISM IN THESE OTHER TISSUES
  43. 43. RECEPTORS FOR A PARTICULAR HORMONE ARE ONLY EXPRESSED IN CELLS WHERE THE HORMONE ACTS. MORE ACTION-MORE RECEPTORS UNDERSTAND INSULIN EXAMPLE (IT IS AN EASY ONE)
  44. 44. Hormone response effected by Receptor Levels and hormone levels Have high levels of receptor in tissue that are primary responders
  45. 45. Hormones act via own receptors at normal concentrations High hormone concentration can act on similar receptors NE and Epi Oxy and vaso IGF-1 and insulin
  46. 46. In most cases, a maximum biological response to a hormone is achieved when only a small % of the receptors are occupied. WHY ?
  47. 47. <ul><li>There are 4 classes of membrane bound receptors </li></ul><ul><li>Those that are enzymes (have tyrosine kinase activity) </li></ul><ul><li>Ion channels </li></ul><ul><li>Receptors coupled to G proteins </li></ul><ul><li>Receptor that don’t have enzymatic activity (utilize the JAK STAT pathway) </li></ul>
  48. 48. Peptide hormones act via PM receptors There are 4 classes of membrane bound receptors 1. Those that are enzymes (have tyrosine kinase activity)
  49. 49. <ul><li>There are 4 classes of membrane bound receptors </li></ul><ul><li>Those that are enzymes (have tyrosine kinase activity) </li></ul><ul><li>This means the receptor itself has enzymatic activity when the hormone is bound. </li></ul><ul><li>Usually KINASE activity </li></ul>
  50. 50. KIN ASE activity X-OH X-OP Phosphat ase activity Amino acid substrates S T Y
  51. 51. <ul><li>There are 4 classes of membrane bound receptors </li></ul><ul><li>Those that are enzymes </li></ul><ul><li>Insulin receptor </li></ul><ul><li>EGF receptor </li></ul><ul><li>NGF receptor </li></ul><ul><li>Usually induce cascade effect </li></ul>
  52. 52. 2. Ion channels Ligand binding changes the conformation of the receptor so that specific ions flow through it; the resultant ion movements alter the electric potential across the cell membrane. The acetylcholine receptor at the nerve-muscle junction
  53. 53. There are 4 classes of membrane bound receptors 3. Receptors coupled to G proteins (7TMDS) Odorant Receptors Adrenergic receptors (epi and NE)
  54. 62. 7 hydrophobic membrane spanning domains Internal G protein interacting region N terminal glycosylation C-term phosphorylation sites
  55. 63. Mediate signals for proteins, peptides, NT Odorants and photons
  56. 64. hydrophobic membrane spanning domains 22 -28 hydrophobic AA
  57. 65. Many of the receptors for peptide hormones and NTs are linked to G proteins
  58. 66. Most neuropeptide receptors
  59. 67. There are 4 classes of membrane bound receptors 4. Receptor that don’t have enzymatic activity (utilize the JAK STAT pathway) Examples GH receptor, PRL receptor Cardiotrophin 1 (CT1), CNTF receptor Leptin receptor
  60. 68. The JAK/STAT Signaling Pathway
  61. 69. JAK STAT pathway Ligand binds receptor Receptor Dimerizes Receptor associate with JAK kinase JAK phosphorylates receptor STAT associates with phosphorylated receptor JAK phosphorylated STAT STAT forms dimer and translocates to the nucleus to regulate transcription
  62. 70. JAK STAT pathway Used by Growth Hormone And prolactin And EPO Interferons
  63. 72. <ul><li>There are 4 classes of membrane bound receptors </li></ul><ul><li>Those that are enzymes (have tyrosine kinase activity) </li></ul><ul><li>Ion channels </li></ul><ul><li>Receptors coupled to G proteins </li></ul><ul><li>Receptor that don’t have enzymatic activity (utilize the JAK STAT pathway) </li></ul>
  64. 74. Second Messengers of Hormone Action Cyclic Nucleotides Generated by Nucleotide cyclyzing enzymes-located on inner surface of PM ATP cAMP Adenylate cyclase GTP cGMP guanylate cyclase
  65. 76. cAMP and cGMP Combine with cyclic dependent protein kinases cAMP associates and activates cyclic dependent protein kinase A (PKA) 2 Regulatory and 2 Catalytic subunits cAMP binds R subunits which frees C which has enzymatic activity
  66. 77. Genomic actions of cAMP Many second messengers, result in immediate response Others have actions which are blocked by actino. D or Cyclohex. For example, PKA activates CREB cAMP response element binding protein CREB binds gene promoters are CRE elements (camp responsive elements) to modulate transcription
  67. 79. Enzyme phos. Leads to a cascade effect Results in amplification So little hormone or second messenger have a large effect X-OH X-OP y-OH y-OP z-OH z-OP
  68. 81. cAMP and cGMP rapidly metabolized Action of kinases Reversed by phosphatases When initiate a response, also initiate a means to inhibit response
  69. 82. cAMP and cGMP get Inactivated by phosphodiesterases (PDE) To 5’AMP or 5’ GMP cyclase Activity of PDEs inhibited by methylxanthines Caffeine, theophylline, and theobromine Increased cAMP/signaling
  70. 83. Many hormones use adenylate cyclase to cause a physiological response. Some activate this enzyme Others can inhibit
  71. 86. Receptor G-protein interactions mediate different signal transduction pathways PLC Adenylate cyclase PLA2 Ion Channel* *G proteins don’t always induce Second Messenger
  72. 87. Some Second Messengers
  73. 88. <ul><li>Multiple Membrane Messengers </li></ul><ul><li>PI (phosphoinosotides) are phospholipids in PM of all eukaryotes </li></ul><ul><li>Breakdown to form second messengers </li></ul><ul><li>AA </li></ul><ul><li>IP3 </li></ul><ul><li>DAG </li></ul>
  74. 91. Protein Kinase C (PKC) Multifunctional enzyme Many types Ca++ dependent and independent Inactive until associates with PM then activated by DAG Active enzyme is membrane bound PKC-many roles including growth and proliferation. Activated by most peptide mitogenic hormones
  75. 93. Eicosanoids and Hormone Action Eicosanoids are produced by cells in response to some hormones Intracellular second messengers 1982 Nobel Prize They are rapidly degraded, so they are not transported to distal sites within the body.
  76. 94. Eicosanoids and Hormone Action Common Eicosanoid PGE2 PGF2a Prostacylin (PGI2) PGI2 and PGE2 can activate adenylate cyclase
  77. 95. Eicosanoids are produced exclusively within the PM Primarily derived from AA that is release from phospholipids via action of PLA2 AA can also produce leukotrienes AA----5HPETE by 5’lipoxgenase
  78. 97. Prostacyclin (PGI 2 ) Produced by blood vessel wall Most potent natural inhibitor of blood platelet aggregation Activates AC which increase cAMP Which inhibits platelet aggregations
  79. 98. ThromboxaneA2 specific product of the platelets 2 types of prostaglandins thromboxane (vasoconstrictor) and PGI2 (vasodilator) Opposite effects A vasoconstrictor is any substance that acts to constrict blood vessels Vasoconstrictors are also used clinically to increase blood pressure or to reduce local blood flow.
  80. 99. Leukotrienes Made by leukocytes Important in vascular contraction and permeability Lots of diseases associated with increased levels Asthma Chronic bronchitis, CF, septic shock Psoriasis, Inflamm Bowel Dis
  81. 100. Many prostaglandins act as local mediators -paracrine and autocrine signaling Destroyed near the site of their synthesis. Modulate the responses of other hormones and can have profound effects on many cellular processes. Certain prostaglandins cause blood platelets to aggregate and adhere to the walls of blood vessels. Because platelets play a key role in clotting blood and plugging leaks in blood vessels, these prostaglandins can affect the course of vascular disease and wound healing; aspirin inhibits their synthesis by acetylating prostaglandin H2 synthase.
  82. 101. Not all hormones work via cell surface receptors Steroid and Thyroid Hormone receptors Receptors are present in cytosol and/or nucleus Estrogen and estrogen receptor (ER) Testosterone and androgen receptor (AR) Thyroid hormones and Thyroid hormone receptors (TR) Cortisol and Glucocorticoid receptor (GR)
  83. 102. Hormones enter cell by diffusion (hydrophobic) Usually bind receptor in cytosol (displace a binding protein) Translocates to the nucleus Binds promoter at specific elements Regulates gene expression
  84. 103. Hormone/receptor complex translocates to the nucleus and binds promoters at hormone response element EREs (estrogen response elements) AREs TREs GREs
  85. 104. The hormone and receptor complex directly bind response elements with the DNA
  86. 106. Can all Communicate with the nucleus
  87. 107. Hormones are complex Lots of things to be studied regarding hormones (see next slide) Methods are used to perform ENDOCRINOLOGY EXPERIMENTS?
  88. 108. <ul><li>General considerations </li></ul><ul><li>Source </li></ul><ul><li>Structure determination * (inject or oral) </li></ul><ul><li>Biosynthesis </li></ul><ul><li>Control of secretion </li></ul><ul><li>Cellular mechanism of secretion </li></ul><ul><li>Circulation and metabolism </li></ul><ul><li>Biological actions/functions </li></ul><ul><li>Mechanisms of action </li></ul>
  89. 109. Histological and cytological studies Hypertrophic- enlarged This means bigger cells Contain more ER and Golgi Opposite of atrophic Hyperplasia or Hyperplastic An increase in number
  90. 112. Hypertrophic- enlarged This means bigger cells Contain more ER and Golgi Opposite of atrophic
  91. 113. Hyperplasia or Hyperplastic An increase in number
  92. 114. Can have Hypertrophy or Hyperplasia or both depending on condition
  93. 116. Immunocytochemistry This is method to examine peptide or peptide hormone in a tissue. Must have an antibody against that protein. Antibody bind hormone (protein). Use Fluorescent dye to bind antibody to visualize location of protein.
  94. 117. Immunocytochemistry to show marker of Hodgkins lymphoma
  95. 119. Immunocytochemistry This is method CAN ALSO BE used to determine what tissue produces a hormone and/or where in the cell it is localized
  96. 121. Surgical Methods Endocrine organs can be transplanted to a new location Ectopic-abnormal site Hypophysectomy-removal of pituitary Pituitary target organs become atrophic
  97. 123. Ectopic-abnormal site
  98. 124. Removal of both members of paired (bilateral roans) such as adrenals or gonads usually leads to COMPLETE loss of dependent tissue/organ FUNCTION. Only unilateral (one) removal Have compensatory hypertrophy To account for ablated organ
  99. 125. Parabiosis Animals are sutured together and share vascular systems Remove endocrine gland of one mouse, the organs of other animal will hypertrophy. Chemical communication between animals
  100. 126. Obese gene -genetic defect in this gene causes obesity and type II diabetes The obesity gene codes for a hormone called leptin that is made exclusively in FAT
  101. 127. diabetes gene -genetic defect in this gene causes obesity and type II diabetes The diabetes gene codes for the leptin receptor which is primarily expressed in the hypothalamus
  102. 128. Ob/ob mice-no leptin db/db-no leptin receptor 2 commonly used rodent models of type II diabetes
  103. 129. Parabiosis of ob/ob and db/db mice Ob/ob mice-no leptin db/db-no leptin receptor
  104. 130. Gray mouse is wild type Ob mouse and wild type-get leaner ob mouse. Sharing Hormone
  105. 131. db mouse and wild type-db does not get leaner because of defective receptor, not a problem with the hormone.
  106. 132. db mouse and ob mouse-ob mouse gets better as it gets circulating hormone from db mouse. Db mouse does not improve because of defective receptor
  107. 133. This pivotal parabiosis experiment showed that ob gene coded for circulating factor and that db did not .
  108. 135. Positional cloning is method to identify and clone the gene that creates a phenotype. So-finding the genotype
  109. 136. Positional cloning is method to identify and clone the gene that creates a phenotype. So-finding the genotype Obese mice-defect in obese gene Took over 10 years to find gene Same with diabetes gene
  110. 138. Obese mice-defect in obese gene Found was fat specific
  111. 139. Chemicals Alloxan or streptozoticn destroy islets which produce insulin-induce Type I diabetes in an animal Cobalt chloride destroy glucagon secreting cells Induce diabetes chemically or surgically
  112. 140. Hormone Replacement Therapy (HRT) Reverse the undesirable effects of hormone loss following surgery or disease state or age. Children lacking GH are given this hormone to avoid stunted growth
  113. 141. Immunological Neutralization of Hormone activity Antibodies against a hormone injected. Bind hormone and inhibit its action Mostly used as Experimental rather than treatment approach to understand the actions of specific hormones Inject anti-NGF antibodies no growth and dev’t of SNS
  114. 142. Bioassays Different approaches to examine hormone activity Based on activity (enzymatic) Or association with another molecule
  115. 143. Bioassays Different approaches to examine hormone activity Structure-Activity Studies Site directed mutagenesis
  116. 144. Bioassays Different approaches to examine hormone activity Structure-Activity Studies Site directed mutagenesis
  117. 145. Structure-Activity Studies Mutate part of the gene or one base of the gene to determine if that part is important in hormone activity and function Site directed mutagenesis
  118. 146. Radioisotope Studies I 125 take up by thyroid Radioactive Ca measured P to perform phosphorylation studies Half life studies Kinase studies
  119. 147. Radioisotope Studies I 125 take up by thyroid
  120. 148. Chemical ID 1 0 - amino acid sequence 2 0 – secondary 3 0 – 4 0 – association with other proteins Modifications like glycosylation, phosphorylation and sulfation
  121. 149. RIA Detection of hormones at minute concentrations. Need an antibody
  122. 150. RIA Detection of hormones at minute concentrations. Need an antibody
  123. 151. RIA Nobel Prize in Medicine (1977) to Rosalyn Yalow
  124. 152. Electrophysiology membrane potential
  125. 153. Pharmacological experiments Actinomycin D-inhibits transcription Cycloheximide-inhibits translation Colchicine-disrupt microtubules Cytochalasin B-disrupts microfilament
  126. 154. Pharmacological experiments Actinomycin D and Cycloheximide Can be used to determine if an action of a hormone is genomic
  127. 155. Specific Example To determine if effect of a hormone is dependent on new proteins synthesis, treat target cells with CH then look at hormone action. If action is blocked, know the effect is genomic
  128. 156. Pharmacological experiments Colchicine and Cytochalasin can be used to tell if signaling or secretion is dependent on cytoskeleton
  129. 157. Tissue Extracts and purification Type I diabetics need daily injections of insulin Used to come from pigs, cattle, horse. Slaughterhouse blood Contaminants from animals Specificity issues Insulin now made recombinant Sheep melatonin Bovine GH
  130. 158. Tissue Extracts and purification Disadvantage of using hormones purified from animals or Slaughterhouse blood -Contaminants from animals -Specificity issues -Cost, much cheaper to make recombinantly Sheep melatonin Bovine GH
  131. 159. Recombinant DNA methods Way in which we make insulin Genetic engineering in various species Fish, mice, rats.
  132. 160. Transgenic Animals introduce gene in animal -Usually replace wild type with a mutant -Or express gene from a different promoter.
  133. 162. Transgenic Mice over expressing Tropomodulin Have enlarged right atrium and ventricle and are larger
  134. 163. Labeled for two different proteins which are normally present in myofibrils. The alternating bands of tropomodulin (green) and alpha-actinin (red) show the dense packing of myofibril throughout the interior of the cell.
  135. 164. The normal alternating pattern of tropomodulin and alpha-actinin immunoreactivity has been disturbed. The yellow color indicates colocalization of both red and green labels (an abnormal distribution). Transgenic mice with this level of tropomodulin overexpression suffer from cardiomyopathy
  136. 165. transgenic mice that overexpress TGFß1 in the CNS animals developed severe hydrocephalus transgenic colony serves as a model of congenital hydrocephalus
  137. 166. GH receptor knockout
  138. 167. GFP mice
  139. 168. overexpress neurotrophin-3 (NT-3) in skeletal muscle When lifted by the tail, wildtype extend their hindlimbs and digits. In contrast, all transgenic NT-3 mice retract their hindlimbs to the body and clench their paws in a &quot;clasping phenotype&quot;
  140. 169. Transgenic mice has different coat color Transgenic mice extremely useful in studying diseases
  141. 170. Test is Feb 10 STUDY your NOTES and the study guide

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