A type of hormone (a mineralocorticoid) secreted from the adrenal cortex into the blood. Its primary role in humans is to stimulate sodium reabsorption and potassium excretion by the kidneys, in order to maintain electrolyte and water balance. Excessive secretion is known as aldosteronism, indicated by potassium depletion, sodium retention, and hypertension.
Aldosterone is a steroid hormone produced by the outer-section (zona glomerulosa) of the adrenal cortex in the adrenal gland to regulate sodium and potassium balance in the blood. Acting on mineralocorticoid receptors (MR) on principal cells in the distal tubule of the kidney nephron, it increases the permeability of their apical (luminal) membrane to potassium and sodium and activates their basolateral Na pumps, stimulating ATP hydrolysis, reabsorbing sodium (Na) ions into the urine.
Aldosterone is responsible for the reabsorption of about 2% of filtered sodium in the kidneys, which is nearly equal to the entire sodium content in human blood under normal GFR (glomerular filtration rate). Some of the transcribed genes are important for transepithelial sodium transport, including serum and glucocorticoid-induced kinase, channel-inducing factor, K-ras2A, and three subunits of the epithelial sodium channel.
Aldosterone synthesis is stimulated by increased plasma angiotensin II or potassium levels, which are present in proportion to plasma sodium deficiencies. If decreased blood pressure is detected, the adrenal gland is stimulated by these stretch receptors to release aldesterone, which increases sodium reabsorption from the urine, sweat and the gut.
User Comments Add a comment…