1. The kidneys reabsorb large amounts of water and solutes per day through the renal tubules, including 179 L of water, 1 kg of NaCl, and various other substances. 2. Substances are divided into three groups for reabsorption - actively reabsorbed, reabsorbed in small amounts, and non-reabsorbed. Na+, Cl-, water and other important substances are actively reabsorbed. 3. Reabsorption is regulated by hormones like aldosterone and antidiuretic hormone to control water and electrolyte balance in the body.

1. WATER-MINERAL
METABOLISM

4. Reabsorbtion. Lenght of renal tubules is about 100 km. So, all
important for our organism are reabsorbed during passing these
tubules. Epitelium of renal tubules reabsorb per day 179 L of
water, 1 kg of NaCl, 500 g of NaHCO3, 250 g of glucose, 100 g
of free amino acids.
All substances can be divided into 3 group:
1. Actively reabsorbed substances.
2. Substances, which are reabsorbed in a little amount.
3. Non-reabsorbed substances.
To the first group belong Na+, Cl-, Mg2+, Ca2+, H2O, glucose
and other monosaccharides, amino acids, inorganic phosphates,
hydrocarbonates, low-weight proteins, etc.
Na+ reabsorbed by active transport to the epitelium cell, then
– into the extracellular matrix. Cl- and HCO3- following Na+
according to the electroneutrality principle, water – according to
the osmotic gradient. From extracellular matrix substances go
to the blood vessels. Mg2+ and Ca2+ are reabsorbed with help of
special transport ATPases. Glucose and amino acids use the
energy of Na+ gradient and special carriers. Proteins are
reabsorbed by endocytosis.
Urea and uric acid are little reabsorbable substances.
Creatinin, mannitol, inulin and some other substances are non-
reabsorbable.
Some substances (K+, ammonia and other) are secreted into

5. Peculiarities of biochemical processes in
kidney.
Kidney have a very high level of metabolic
processes. They use about 10 % of all O2, which
used in organism. During 24 hours through
kidney pass 700-900 L of blood. The main fuel for
kidney are carbohydrates. Glycolysis, ketolysis,
aerobic oxidation and phophorillation are very
intensive in kidney. A lot of ATP formed in result.
Kidney have plenty of different enzymes: LDH (1, 2,
3, 5), AsAT, AlAT. Specific for kidney is alanine
amino peptidase, 3rd isoform.

8. Organic compounds of urine.
Proteins. Healthy people excretes 30 mg of proteins per day. As
a rule these are low weight proteins.
Urea. This is main part of organic compounds in urine. Urea
nitrogen is about 80-90 % of all urine nitrogen. 20-35 g of urea
is excreted per day in normal conditions.
Uric acid. Approximately 0,6-1,0 g of uric acid is excreted per
day in form of different salts (urates), mainly in form of sodium
salt. Its amount depends from food.
Creatinin and creatin. Near 1-2 g of creatinin is excreted per
day, what depended from weight of muscles. This is the
constant for each person. Men excrete 18-32 mg of creatinin
per 1 kg of body weight per day, women – 10-25 mg. Creatinin
is non-reabsorbable substance, so this test used for evaluating
of renal filtration.
Amino acids. Per day healthy person excretes 2-3 g of amino
acids (free amino acids and different low weight molecule
peptides). Also products of amino acids metabolism can be
found in the urine.
Couple substances. Hypuric acid (benzoyl glycine) is excreted in
amount 0,6-1,5 g per day. This index increases after eating a
lot of berries and fruits, and in case of protein’s decay in the
intestines.

9. Indican (potassium salt of indoxylsulfuric acid). Per day excrition of indican is
about 10-25 g. Increasing of indican’s level in urine is due to inrtensification of
decay proteins in the intestines and chronic diseases, which are accompanied by
intensive decopmosition of proteins (tuberculosis, for example).
Organic acids. Formic, acetic, butyric, β-oxybutyric, acetoacetic and some other
organic acids are present in urine in a little amount.
Vitamines. Almost all vitamines can be excreted via kidney, especially, water-soluble.
Approximately 20-30 mg of vit C, 0.1-0.3 mg of vit B1, 0.5-0.8 mg of vit B2 and
some products of vitamine’s metabolism. These data can be used for evaluating of
supplying our organism by vitamines.
Hormones. Hormones and their derivates are always present in urine. Their amount
depends from functional state of endocrinal glands and liver. There is a very wide
used test – determination of 17-ketosteroids in urine. For healthy man this index is
15-25 g per day.
Urobilin. Present in a little amount, gives to urine yellow colour.
Bilirubin. In normal conditions present in so little amount that cannot be found by
routine methods of investigations.
Glucose. In normal conditions present in so little amount that cannot be found by
routine methods of investigations.
Galactose. Present in the newborn’s urine, when digestion of milk or transformation of
glalactose into glucose in the liver are violated.
Fructose. It is present in urine very seldom, after eating a lot of fruits, berries and
honey. In all other cases it indicates about liver’s disorders, diabetes mellitus.
Pentoses. Pentoses are excreted after eating a lot of fruits, fruit juices, in case of
diabetes mellitus and steroid diabetes, some intoxications.
Ketone bodies. In normal conditions urine contains 20-50 mg of ketone bodies and
this amount cannot be found by routine methods of clinical investigations.
Porphyrines. Urine of healthy people contains a few I type porphyrines (up to 300
mkg per day).

10. Regulation of urine formation.
Na-uretic hormone (produced in heart) decrease
reabsorbtion of Na+, and quantity of urine
increased.
Aldosteron and some other hormones (vasopressin,
renin, angiotensin II) increase Na-reabsorbtion
and decrease quantity of urine.
Role of kidney in acid-base balance regulation.
Kidney have some mechanisms for maintaining
acid-base balance. Na+ reabsorbtion and H+
secretion play very important role.
1. Primary urine has a lot of Na2HPO4 (in dissociated
form). When Na+ reabsorbed, H+ secreted into
urine and NaH2PO4 formed.

11. 2. Formation of hydrocarbonates. Inside
renal cells carboanhydrase forms from CO2
and H2O H2CO3, which dissociated to H+
and HCO3-. H+ excreted from cell into urine
(antiport with Na+) and leaded with urine.
Na+ connect with HCO3-, NaHCO3 formed
and go to the blood, thereupon acidity
decreased.
3. Formation of free ammonia. NH3 used for
formation of NH4+ (H+ ion associted), and
different acid metabolites excreted as
ammonia salts.

12. Role of kidney in water balance regulation.
Excessive entrance of water leads to dilution of
extracellular fluid. Decreasing of osmolality
inhibits secretion of antidiuretic hormone. Walls
of collective tubules stay non-penetrated to water
and dilutive urine formed.
If volume of blood circulation increases, circulation
in kidney increases also and hyperosmotic
medium of kidney medulla removed. Some
substances in these conditions return into blood.
So, excess of water carried with urine and a lot of
soluble substances are reabsorbed into blood.
After water loading stopped, hyperosmolality in
kidney medulla returns for previous stage during
some days.

14. Melting point of water – 0 oC; boiling point – 100 oC.
Water plays an important role in the thermal regulation of
living organisms. Water's high heat capacity coupled with the
high water content found in most organisms (between 50%
and 95%, depending on species) contributes to the
maintenance of an organism's internal temperature.
Water is a remarkable solvent. Water's ability to dissolve a
large variety of ionic and polar substances is determined by its
dipolar structure and its capacity to form hydrogen bonds.
Salts such as sodium chloride (NaCI) are held together by
ionic (or electrostatic) forces. They dissolve easily in water
because dipolar water molecules are attracted to the Na+ and
Cl- ions.
Organic molecules with ionizable groups and many neutral
organic molecules with polar functional groups also dissolve in
water. Their solubility is due primarily to the hydrogen bonding
capacity of water. Nonpolar compounds are not soluble in
water. Because they lack polar functional groups, such
molecules cannot form hydrogen bonds.

15. The state and distribution of water in the organism.
There are two water compartments in the body:
- Intracellular water
- Extracellular water
Extracellular fluid is divided into:
- interstitial fluid
- Plasma
Biological role of water:
Water is an essential constituent of cell structures
and provides the media in which the chemical reactions of
the body takes place and substance are transported.
It has a high specific heat for which, it can absorb or
gives off heat without any appreciable change in
temperature.
It has a very high latent heat. Thus, it provides a
mechanism for the regulation of heat loss by sensible or
insensible perspiration on the skin surface.
The fluidity of blood is because of water.

17. Distribution of water in an adult man, weighing 70 kg
Body weight
Volume (l)
Compartment (%)
Total 60 42
ICF 40 28
ECF 20 14
Interstitial fluid 15 10,5
Plasma 5 3,5

18. Water balance. Endogenous water.
Water intake.
Water is supplied to the body by exogenous and endogenous
sources.
Exogenous water: water intake is highly variable which may
range from 0,5-5 liters. Ingestion of water is mainly
controlled by a thirst centre located in the hypothalamus.
Endogenous water: the metabolic water produced within the
body is the endogenous water. This water (300-350
ml/day) is derived from the oxidation of foodstuffs. It is
estimated that 1g each of carbohydrate, protein and fat,
respectively, yield 0,6 ml, 0,4 ml and 1,1 ml of water.
Water output.
Water losses from the body are variable. There are four
distinct routes for the elimination of water from the body:
urine, skin, lungs and feces.

20. Regulation of Water Metabolism
• Antidiuretic hormone or Vasopressin which has got the property to
enhance water reabsorption
2. Hypothalamus known as a thirst centre. Besides this,
osmoconcentration of plasma also stimulates supraoptic and
paraventricular nuclei
3. Adrenal Cortex. Aldosterone has controll excretion of sodium and
potassium by the kidneys
4. Rennin-Angiotensin system. Angiotensin II stimulates the synthesis
and secretion of aldosterone and the release of vasopressin, and
thereby increases renal absorption of Na+ and H2O.
5. Prostaglandins. They may also increase urinary loss of water by
inhibiting the antidiuretic effect of vasopressin and by increasing the
urinary sodium.
6. Solutes. Osmotic effect of Na+ helps to retain water in extracellular
fluids. Elevation in plasma Na+ raises the ECF volume in primary
aldosteronism while an increase in urinary Na+ raises the urinary water
output in Addison's disease. K+ helps to retain water in the cells,
whereas, plasma proteins do help to retain water in the body by their
osmotic effects. Increase in urinary urea or excretion of glucose in urine
increases osmotically the urinary loss of water (osmotic diuresis).

21. The general biological role of mineral salts and
chemical elements in human organism:
- plastic role (mineral salts are included in a structure of
bones, dens, cartilages, organic macromolecules etc.);
- osmotic pressure maintenance;
- they are the constituents of buffer systems (bicarbonate and
phosphate buffer systems);
- they are the constituents of the certain hormones,
coenzymes, enzymes active canters;
- they take part in the formation of membrane potential.
Macro-, micro- and ultramicroelements.
Macroelements - are those the contents of which in
organism is more than 10-2 % (P, S, Ca, Na, K, Mg) and
day necessity is more than 100 mg per day.
The content of microelements in human body is from 10-2 to
10-5 % (I, F, Se, Co, Cu, Zn).
Ultramicroelements - are those the contents of which in
organism is less than 10-5 % (Pb, Au, Mo and others).

22. Biological role of potassium and sodium.
- potassium promotes the protein synthesis by ribosomes;
- number of enzymes require K+ for maximum activity (for
example in the glycolitic sequence K+ is required for maximum
activity of pyruvate);
metabolically supported gradients of Na+ and K+ across the cell
membrane are involved in the maintenance of the membrane
potential of excitable tissues, which is the vehicle for
transmission of impulses in the form of an action potential;
K+ ions enhance the function of parasympathetic nervous system
and acetylcholine action on the nervous terminals in muscles;
K+ ions reduce the exciting influence of ions on muscles;
a proper plasma K+ level is essential for the normal heart
functioning more precisely for relaxation of myocardium

24. sodium ions play the main role in regulation of
osmotic pressure and retention of water in an
organism;
- sodium chloride of blood plasma is the main origin
of hydrochloric acid formation;
- Na+ ions take part in the formation of a short-
term memory.
Sodium content in blood plasma is 130-150 mmol/l.
Potassium content in the blood is 3.4-5.3 mmol/l,
this is only 2 % of all potassium content in the
human body.

26. Regulating of potassium and sodium
metabolism
The main hormones, regulating Na+ metabolism, are
mineralocorticoids and atrial natriuretic peptide (ANP). The
mineralocorticoids, aldosterone and deoxycorticosterone,
increase Na+ reabsorption from the tubular fluid and
therefore their excess causes Na+ retention. In addition,
these hormones increase the elimination of more K+ and
Na+ in the urine.
A greater formation of aldosterone (primary aldosteronism
or Conn’s syndrome) is associated with an increased Na+
retention in the body (hypernatriemia) with hypokaliemia
and metabolic alkalosis. Conditions like congestive heart
failure, cirrhosis of the liver and nephrotic syndrome also
lead to a greater formation of aldosterone (secondary
aldosteronism).

28. CHLORIDE
MAJOR ANION OF ECF.
SECRETED IN GASTRIC JUICE
99% REABSORBED UNDER NORMAL PH
CONDITIONS.
CHLORIDE SHIFT
DECREASED IN ACIDOSIS

29. BICARBONATE
PRESENT IN ECF
BUFFERING ACTION
REABSORBED IN TUBULE AS CO2
FOR HYDROGEN ION.

30. Functions of calcium in the body:
1. Calcium salts take part in bone and tooth development.
Deficient supply of calcium leads to rickets in children
and osteomalacia in adults.
2. The clotting of blood needs calcium ions
3. By regulating the membrane permeability calcium
ions control the excitability of nerves.
4. Calcium ions act as a cofactor or activator of certain
enzymes. A protein namely calmodulin is present within
cells, which can bind calcium.
5. Calcium ions take part in the contraction of muscle
including heart muscle and are involved in the
excitation-contraction coupling mechanism.
6. Calcium ions are responsible for initiating contraction in
vascular and other smooth muscles. Calcium ions enter
through specific channels just as is the case with cardiac
muscle.
• Calcium is essential for maintaining the integrity of
capillary wall.
• Calcium ions are involved in exocytosis and thus have an
important role in stimulus-secretion coupling in most
exocrine and endocrine glands.
• Some hormones exert their influence through Ca2+.

31. CALCIUM
• CALCITONIN- decreases bone
resorption

32. Biological role of magnesium.
- Half of magnesium occurs in the inorganic matter
of bones and the rest occurs in soft tissues and
body fluids. Blood plasma contains 0.8-1.2 mmol/
l of Mg.
- Nuts, legumes, chlorophyll and whole grains are
very good sources of magnesium.
Functions of Mg in the body:
1. It takes part in the formation of complex salts of
bones and teeth.
2. It acts as a cofactor for many enzymes.
3. It serves to decrease neuromuscular irritability.
Effects of a high serum Mg2+ level -
Experimentally, a serum Mg2+ level of 8 mmol/l
produces immediate and profound anesthesia and
paralysis of voluntary muscles. These effects can
be reversed by an intravenous injection of a
corresponding amount of Ca2+. Serum Mg2+ tends
to rise in renal failure.

33. Biological role of iron.
Iron is part of the structure of many important
body constituents, e.g. hemoglobin, myoglobin,
enzymes like cytochromes, catalase, xanthine
oxidase, mitochondrial α-glycerophosphate
oxidase, etc. The iron content of hemoglobin is
0.34%.
Dietary sources - Animal sources are the best
and include liver, red meat and egg yolk. Of the
vegetables, spinach and other leafy vegetables
are good sources. Dried fruits also contain
appreciable amounts of iron.

34. The role of vitamins and hormones in regulation
of calcium metabolism.
The main hormones regulating Ca metabolism
are calcitonin and parathyroid hormone.
Calcitonin is a hormone which is produced by the parafollicular
cells (also called clear or C cells) of the thyroid gland. It lowers
the plasma calcium level as it antagonizes the action of the
parathyroid hormone. Calcitonin decreases bone resorption and
increases the deposition of calcium in bones. It also increases
urinary loss of Ca2+ by inhibiting the Ca2+ reabsorption in the
proximal convoluted tubules.
Parathyroid hormone increases intestinal absorption of calcium,
it also mobilizes bone calcium and causes a marked
hypercalcemia. It also increases calcium absorption from the
distal convoluted tubules of the kidney.
Active vitamin D greatly increases the absorption of calcium by
increasing the amount of the specific transport protein responsible
for active transport of calcium in the proximal small intestinal
wall. Effect of parathyroid hormone is less marked than that of
vitamin D; it is mediated through conversion of vitamin D to its
active form.

35. Biological role of phosphorus
An adult body contains 1 kg phosphate and it is found in
every cell of the body. Most of it (about 80%) occurs in
combination with calcium in the bones and teeth. About
10% of body phosphorus is found in muscles and blood in
association with proteins, carbohydrates and lipids.
Biochemical functions:
- Phosphorus is essential for the development of bones and
teeth.
- It plays a central role for the formation and utilization of
high-energy phosphate compounds (ATP, GTP, creatine
phosphate etc.).
- Phosphorus is required for the formation of phospholipids,
phosphoproteins and nucleic acids (DNA and RNA).
- It is essential component of several nucleotide coenzymes
eg. NAD, NADP, pyridoxal phosphate, ADP, AMP.
- Several proteins and enzymes are activated by
phosphorylation.
- Phosphate buffer system is important for the maintenance
of pH in the blood as well as in the cells.

36. Regulation of Renal Phosphate
Excretion
PTH play important role in regulating
phosphate concentration through 2
effects:
1) PTH promotes bone resorption,
thereby dumping large amounts of
phosphate ions into the ECF from
bones salts
2) PTH decreases the transport
maximum for phosphate by the renal
tubules

37. Role of vitamins and hormones in regulation
of phosphorous metabolism
The hormones – calcitriol, parathyroid hormone
and calcitonin are the major factors that regulate
the plasma phosphorus within a narrow range
(1.2-2.2mmol/l). Calcitriol is the biologically
active form of vit.D. It acts at 3 different levels
(intestine, kidneys and bone). Calcitriol increases
the intestinal absorption of calcium and
phosphate. Calcitriol along with parathyroid
hormone increases the mobilization of calcium
and phosphorus from bone.
Calcitriol is also involved in minimizing the
excretion of Ca and P through the kidney, by
decreasing their excretion and enhancing
reabsorption. Calcitonin inhibits the reabsorption
of phosphorus in kidneys. Thus, calcitonin
decreases the phosphorus content in blood.
Parathyroid hormone decreases serum
phosphorus and increases urinary PO4 (increase
phosphorus excretion in urine).

38. Iodine
The total body contains about 20mg iodine, most of
it (80%) being present in the thyroid gland. The
only known function of iodine is its requirement
for the synthesis of thyroid hormone mainly
thyroxin (T4) and triiodothyronin (T3).
Dietary requirements: 100-150micrograms per day.
Sources: Sea food, drinking water, iodized salt.
Diseases states: Toxic goiter.
Fluoride
Functions: 1.It prevents the development of dental
caries.
2.It is necessary for the proper
development of bones .
3.It inhibits the activities of certain
enzymes.
Dietary requirements: 1-2 mg per day.
Sources: Drinking water.

39. Copper
Functions:
- Its an essential constituent of several enzymes
(cytochrome oxidase, catalase, superoxide
dismutase etc.)
- Its necessary for the synthesis of hemoglobin,
melanin and phospholipids.
- Ceruplasmin has oxidase activity and thereby
facilitates the incorporation of ferric iron into
transferrin.
- Development of bone and nervous system (myelin
requires Cu).
Dietary requirements:2-3 mg per day.
Sources: Liver, kidney, meat, egg yolk, nuts and
green leafy vegetables.
Disease status:
- Copper deficiency (anaemia).
- Menke’s disease (defect in the intestinal absorption
of copper).
- Wilson’s disease

40. Zinc
Functions:
- It is an essential component of several enzymes
(carbonic anhydrase, alcohol dehydrase etc.)
- The storage and secretion of insulin from the beta
– cells of pancreas requires zinc.
- It is require for wound healing.
- It is essential for the proper reproduction.
Dietary requirements: 10-15g per day.
Sources: Meat , fish, eggs, milk, nuts.
Disease status:
Zinc deficiency: poor wound healing, anaemia, loss
of appetite, loss of taste sensation

41. Cobalt
Cobalt is only important as constituent of vit-B12.
The functions of cobalt is same as that of vit B12.
Selenium
Functions:
- Selenium along with vit E, prevents the development of
hepatic necrosis and muscular dystrophy.
- Selenium is involved in maintaining structure integrity
of biological membranes.
- Selenium prevents lipid peroxidation and protect the
cells against the free radicals.
- Selenium binds with certain heavy metals and protects
the body from their toxic effects.
Dietary requirements: 60-250micrograms.
Sources: Liver, kidneys, seafood.
Toxicity: Selenosis is a toxicity due to very excessive
intake of selenium. The manifestation of selenosis
includes weight loss, emotional disturbances,
diarrhea, hair loss and garlic odor in breath.

42. The biological role of chlorine and sulfur.
- Chlorine is contained in all biological liquids of the organism.
- Cl- anions play important role in maintance of blood osmotic
pressure.
- Cl- anions easily pass through the cell membranes (for
example, erythrocytes) and play important role in in
maintenance of a constance and regulation of hydrogen ions
concentration.
- Cl- anions also play important role in formation of stomach
hydrochloric acid.
- In the organism sulfur exists both as organic and inorganic
compounds.
- It is a component of sulfurs containing amino acids, proteins.
A lot of sulfur is included into the connective tissue
(epithelium, nails, hair). Sulfur is a constituent of some
hormones (insulin, pituitary hormones), enzymes,
coenzymes, peptide glutathione, bile acid (taurin). Like
phosphorus sulfur takes part in formation of macroergic
bounds. Sulfates form conjugates with different toxic
substances in liver and then these conjugates are excreted
from the organism. Thus sulfur executes the
decontaminating function.

43. The role of vitamins and hormones in regulation of water-salt
metabolism.
Vitamin D regulates the calcium homeostasis in organism. It stimulates
the absorption of calcium ions in the intestine and renal canaliculus.
Vitamin D increases the Ca2+ level in organism.
Aldosteron promote the sodium reabsorption in renal canaliculuses and
excretion of potassium ions by kidneys and skin. Thus aldosteron
results in hypernatriemia and hypokaliemia.
Na-diuretic hormone retards the reabsorption of Na in renal
canaliculuses.
Calcitonin promotes the transition of calcium from blood in bones and
inhibits the reabsorption of phosphorus in kidneys. Thus, calcitonin
decreases the Ca and P contents in blood.
Parathyroid hormone promotes the transition of calcium from bones to
blood; promotes the absorption of Ca in the intestine. Thus,
parathyroid hormone increases the Ca amount in blood. Parathyroid
hormone also inhibits the reabsorption of phosphorus in kidneys and
decreases the P amount in blood.
Lipotropic hormone decreases the Ca amount in blood.
Vasopressin - activates the hyaluronidase. This enzyme splits the
hyaluronic acid. The permeability of membranes is increased and
reabsorption of water in kidneys is increased too. As result the day
diuresis is decreased.
Insulin activates Na+, K+-ATP-ase (transition of K into the cells and Na
from the cells).

44. Normal Laboratory Values
Parameters Values
Sodium 135-145 meq/L
Potassium 3.5-5.0 meq/L
Chloride 95-105 meq/L
Bicarbonate 22-28 meq/L
Calcium 9-11 mg/dL or 2.2-2.6mmo/l
( mmol/l*4 =mg/l)
Phosphate 3.2-4.3 mg/dL or 0.8-1.4 mmol/l
(mmol/l*3=mg/l)
Glucose 70-110 mg/dL ( mg/dl/18 = mmol/dl)
BUN 8-18 mg/dL or 3.3-6.7mmol/l
( mmol/l* 6= mg/l)
Creatinine 0.6-1.2 mg/dL or 60-120 µmol/l
(µmol/l* 0.011=mg/dl)
PLASMA Osmolality 280-295 mOsm/kg
URINE Osmolality 50-1200 mOsm/kg