Chapter 11 presentation Epinephrine (suffix –in,-ine) & Adenocorticotropin (suffix –tropin) By Rowell Angeles
Adrenocorticotropic Hormone (ACTH, adrenocorticotropin) Adrenocorticotropic hormone, as its name implies, stimulates the adrenal cortex. More specifically, it stimulates secretion of glucocorticoids such as cortisol, and has little control over secretion of aldosterone, the other major steroid hormone from the adrenal cortex.
ACTH ACTH is secreted from the anterior pituitary in response to corticotropin-releasing hormone from the hypothalamus. corticotropin-releasing hormone is secreted in response to many types of stress, which makes sense in view of the "stress management" functions of glucocorticoids. Corticotropin-releasing hormone itself is inhibited by glucocorticoids, making it part of a classical negative feedback loop. Additional information on the role of ACTH in regulation of adrenal steroid secretion is presented in the sections on the adrenal gland andglucocorticoids. Within the pituitary gland, ACTH is produced in a process that also generates several other hormones. A large precursor protein named proopiomelanocortin (POMC, "Big Mama") is synthesized and proteolytically chopped into several fragments as depicted below. Not all of the cleavages occur in all species and some occur only in the intermediate lobe of the pituitary.
The major attributes of the hormones other than ACTH that are produced in this process are summarized as follows: Lipotropin: Originally described as having weak lipolytic effects, its major importance is as the precursor to beta-endorphin. Beta-endorphin and Met-enkephalin: Opioid peptides with pain-alleviation and euphoric effects. Melanocyte-stimulating hormone (MSH): Known to control melanin pigmentation in the skin of most vertebrates.
Epinephrine (adrenaline) Adrenaline is a catecholamine and belongs to the family of biogenic amines. Adrenaline is a natural stimulant made in the adrenal gland of the kidney. Its biological name is epinephrine, from the Greek nephros for kidney. Adrenaline is carried in the bloodstream and affects the autonomous nervous system, which controls functions such as the heart rate, dilation of the pupils, and secretion of sweat and saliva. L-adrenaline was the first hormone which could be crystallized. Adrenaline is synthesized in the neurones of the adrenal medulla and stored in the chromaffingranula. An activating signal, which can be induced through a low blood glucose level, triggers the release of adrenaline into the blood. Adrenaline is the body's activator, and is released in response to anxiety, exercise, or fear. Adrenaline can be produced synthetically for medical purposes. Adrenaline is secreted by the adrenal medulla in response to low blood glucose, exercise and stress and causes a breakdown of glycogen to glucose in the liver, encourages the release of fatty acids from adipose tissue, causes vasodilation of the small arteries within muscle and increases cardiac output. Adrenaline is air and light sensitive and forms dark products during decomposition.
The biological functions of adrenaline Adrenaline is the primary catecholamine released from the adrenal medulla in response to stimulation, and is responsible for increases in neural activity (alertness), cardiac output and blood pressure. Adrenaline is a natural antidote to the chemicals released during severe allergic reactions triggered by drug allergy, food allergy or insect allergy. Adrenaline has the opposite effect of insuline. It is a first messenger hormone and will be released when the glucose level in blood is low. Adrenaline belongs to the family of adrenal medulla hormones. The hormone has a big influence on the storage and mobilisation of glycogene and fatty acids and the corresponding metabolic pathways. Adrenaline is a direct-acting sympathomimetic agent exerting its effect on alpha and beta adrenoreceptors. Major effects are increased systolic blood pressure, reduced diastolic pressure, tachycardia, hyperglycaemia and hypokalaemia. It is a powerful cardiac stimulant. It has vasopressor properties, an antihistaminic action and is a bronchodilator. Its action is rapid in onset and of short duration. Adrenaline’s action is thought to be mainly through its alpha agonist activity, mediating powerful peripheral vasoconstricton, increasing diastolic aortic pressure and thereby improving coronary artery blood flow. Adrenaline triggers the adenylatcyclase cascade (or cAMP cascade). This activating cascade effects the mobilisation of glycogene (liver) and triacylglycerines (fat tissue) and a generel increase of the metabolic rate. The resulting rise in blood sugar enables the fermentation of glucose in the muscles. Adrenaline furthermore reinforces these effects, because it increases the secretion of glucagon (a hormone with the same effects as adrenaline) and decreases the release of insulin. Adrenaline works also as neurotransmitter and has an effect on the sympathetic nervous system (heart, lungs, blood vessels, bladder, gut and genitalia). This neurotransmitter will be realeased by nervous stimulation in response to physical or mental stress and binds to a special group of transmembrane proteins.
Usages and indications Adrenaline is used as sympathicomimeticum, broncholyticum and antiasthmaticum. It also is used to staunch or prevent bleedings during surgery or in the case of inner organ bleeding. Adrenaline is administered in combination with local anaesthetics. In this combination, anaesthetics have a longer lasting effect and can be administered in smaller doses. Generally adrenaline is implicated in arousal. Within the body, adrenaline acts in such a way as to maintain an activated state, allowing a higher state of energy to be produced. Within the brain, it is also implicated in emotional states. Adrenaline is used to treat glaucoma. Glaucoma is caused by a blockage in the eye, which prevents fluid leaving the eye, causing pressure to build up within the eye. This can cause pain and discomfort. Adrenaline works by opening. Adrenaline is the recommended first line treatment for patients with anaphylaxis. Anaphylaxis is the clinical syndrome representing the most severe systemic allergic reactions. Adrenaline stimulates adrenoceptors to increase peripheral vascular resistance thus improving blood pressure and coronary perfusion, reversing peripheral vasodilation, and decreasing angioedema.