Aldosterone

aldosterone (ăl'dōstĭrōn`), steroid secreted by the cortex of the adrenal gland. It is the most potent hormone regulating the body's electrolyte balance. Aldosterone acts directly on the kidney to decrease the rate of sodium-ion excretion (with accompanying retention of water), and to increase the rate of potassium-ion excretion. The secretion of aldosterone appears to be regulated by two mechanisms. First, the concentration of sodium ions may be a factor since increased rates of aldosterone secretion are found when dietary sodium is severely limited. Second, reduced blood flow to the kidney stimulates certain kidney cells to secrete the proteolytic enzyme renin, which converts the inactive angiotensinogen globulin in the blood into angiotensin I. Another enzyme then converts angiotensin I into angiotensin II, its active form. This peptide, in turn, stimulates the secretion of aldosterone by the adrenal cortex. Pathologically elevated aldosterone secretion with concomitant excessive retention of salt and water often results in edema.

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aldosterone [al′däs·tə‚rōn]

(biochemistry)

C₂₁H₂₈O₅A steroid hormone extracted from the adrenal cortex that functions chiefly in regulating sodium and potassium metabolism.

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Aldosterone

The steroid hormone found in the biologically active amorphous fraction that remains after separation of the various crystalline steroid substances, such as cortisol and corticosterone, from adrenal extracts. In solution, aldosterone exists as an equilibrium mixture of aldo and lactol forms (see illustration).

Structures for two forms of aldosterone in an equilibrium mixture, (a) aldo and (b) lactol

The chief function of aldosterone is the regulation of electrolyte metabolism, that is, promotion of sodium retention and enhancement of potassium excretion. Aldosterone is the most potent of the hormones which are concerned in this type of metabolism. See Adrenal gland, Hormone, Steroid

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Aldosterone 

(also electrocortin, or aldocortin), an adrenocortical hormone of the group of corticosteroids. It regulates mineral metabolism in the organism and is the basic mineralocorticoid. The molecular mass is 360.43.

Aldosterone was isolated in a crystalline form in 1953 and synthesized in 1959 by Wettstein. It helps to retain sodium ions (Na+) in the organism and to eliminate potassium ions (K+) in the urine, saliva, and perspiration. A deficiency of Na+ and an elevated K+ content in food lead to an increase in the formation of aldosterone. An insufficiency of aldosterone—for example, with adrenalectomy or with Addison’s disease—leading to an acute loss of Na, imperils the life of the organism. The increased formation of aldosterone—for example, with adrenal tumors and certain heart and kidney diseases—causes the retention of water in the organism (edema), an increase in blood pressure, and so forth. The level of aldosterone secretion is related to the relative Na+ and K+ content in the blood plasma and is regulated by the mesencephalon, which secretes the neurohormone adrenoglomerulotropine with the participation of angiotensin and renin, which is formed in the kidneys and the vegetative nervous system.

REFERENCE

Berzin, T. Biokhimiia gormonov. Moscow, 1964. Page 259. (Translated from the German.)

G. L. SHREIBERG