Question

What type of hormone is aldosterone? What receptors does aldosterone utilize? What is the mechanism of action of aldosterone?

Answer 1

Aldosterone, is a mineralocorticoid hormone, a type of  steroid hormone secreted by the zona glomerulosa layer of adrenal glands. The receptors it acts on primarily is the mineralocorticoid receptors in the distal tubules and collecting ducts of the nephron. The main function of aldosterone is to reabsorb water and sodium and excrete potassium in the renal tubules. It acts by binding to and activating a receptor in the cytoplasm of renal tubular cells. The activated receptor then stimulates the production of ion channels in the renal tubular cells, thereby increasing sodium reabsorption into the blood and increasing potassium excretion into the urine.

When ever there is decrease in blood volume, sodium levels are low, potassium levels are high, or if the blood pressure is low, in response to this, kidneys release an enzyme by name renin, this enzyme converts anngitensinogen produced by the liver to the hormone angitensin-1, another enzyme by name ACE found in the lungs, converts angiotensin-1 to angiotensin-2, this stimulates the release of aldosterone from the adrenal gland, the aldosterone than acts on the renal tubules to increases water reabsiorption and retain sodium and excrete potassium, all these results in increase, blood volume, as a result blood pressure also increases, so that normal level is maintained.