Aldosterone

Aldosterone is a steroid hormone synthesized from cholesterol by the enzyme aldosterone synthase. It is formed in the outer-section (zona glomerulosa) of the adrenal cortex of the adrenal gland, as the cells of other sections don't have the corresponding enzyme. It is the sole endogenous member of the class of mineralocorticoids. It helps regulate the body's electrolyte balance by acting on the mineralocorticoid receptor (MR). It diminishes the excretion of sodium (Na+) ions and therefore water, and stimulates the excretion of potassium (K+) ions by the kidneys. more...

Unlike neuroreceptors, classic steroid receptors are located inside of cells. The aldosterone/MR receptor complex binds to the corresponding section of DNA called hormone response element that alters protein synthesis and the transcription of messenger RNA, including serum and glucocorticoid-induced kinase, channel-inducing factor, K-ras2A, and three subunits of the epithelial sodium channel. These genes are important for transepithelial sodium transport.

Aldosterone is synthesized in reaction to increases of angiotensin II or plasma potassium, which are present in proportion to sodium deficiencies. The secretion of aldosterone has a diurnal rhythm, with about 75% of the daily production is secreted between 04:00 and 10:00 each day.

Aldosterone and the kidney

Control of aldosterone release

• The role of baroreceptors
• The role of the juxtaglomerular apparatus
• The role of sympathetic nerves
• The role of the renin-angiotensin system

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