Question

The secretion of aldosterone by the adrenal cortex is directly controlled by
A. Plasma ${{K}^{+}}$ concentration
B. Plasma $Ca$ concentration
C. Level of blood angiotensin
D. Both A and C

Answer 1

Adrenal cortex is a pair of glands situated just above the tips of the two kidneys in the body. It secretes various catecholamine hormones including Aldosterone. The secretion of aldosterone is tightly regulated by various regulatory mechanisms. It is released under conditions of low blood pressure.

Complete answer:
Aldosterone is a steroid hormone that functions to regulate blood pressure and blood volume by increasing the absorption of $N{{a}^{+}}$ ions by the kidney. The topmost layer of the adrenal gland called zona granulosa produces aldosterone from cholesterol. It is transported in blood with the help of albumin as it is hydrophobic.
-Under the conditions of low blood pressure or hypotension, aldosterone is secreted. The hypotension condition results in excess release of rennin which stimulates the increased conversion of angiotensin and this further initiates aldosterone release.
-The production of aldosterone increases when ${{K}^{+}}$ in the blood or the extracellular fluid increases. This increased serum potassium level is determined by carotid artery sensors. So, plasma ${{K}^{+}}$ concentration directly regulates aldosterone release.
-The plasma $Ca$ concentration is involved in the modulation of the renin-aldosterone axis but it does not directly regulate the aldosterone release.
-Lower angiotensin levels prevent the regulation of blood volume and thus increase retention of potassium. This results in excess $N{{a}^{+}}$ ion loss through urine. Thus, aldosterone is released more to absorb more $N{{a}^{+}}$ ions from urine. Thus, angiotensin levels in blood directly regulate aldosterone secretion.
Thus, options A and C are the factors that directly regulate the levels of secretion of aldosterone. So, the right answer is option D which states that options A and C are correct answers.

Note: Aldosterone is directly involved in the regulation of the body’s blood pressure. It belongs to a vast class of mineralocorticoids released by the adrenal gland.