Correct option is B
Renin is an enzyme secreted by the juxtaglomerular (JG) cells of the kidney in response to low blood pressure, sympathetic nervous system activation, or decreased sodium delivery to the distal tubule. It plays a key role in the Renin-Angiotensin-Aldosterone System (RAAS) by catalyzing the conversion of angiotensinogen to angiotensin I, which eventually leads to vasoconstriction and sodium retention to restore blood pressure.
Factors That Inhibit Renin Secretion:
- Increased blood pressure in the afferent arterioles reduces renin secretion by activating the baroreceptor mechanism in the juxtaglomerular apparatus.
- High sodium chloride (NaCl) concentration at the macula densa inhibits renin release through the tubuloglomerular feedback mechanism.
- Angiotensin II (negative feedback) suppresses renin secretion.
Thus, increased blood pressure in the afferent arteriole inhibits renin secretion by signaling the JG cells that blood pressure is sufficient, reducing the need for RAAS activation.
Additional Information
Option (1) Increased plasma catecholamines (Incorrect):
- Catecholamines (epinephrine, norepinephrine) stimulate renin secretion by activating β1-adrenergic receptors on juxtaglomerular cells.
Option (3) Increased sympathetic nerve activity (Incorrect):
- Sympathetic activation increases renin secretion via β1-adrenergic receptors, which leads to vasoconstriction and sodium retention.
Option (4) Prostaglandins (Incorrect):
- Prostaglandins stimulate renin secretion, particularly PGE₂ and PGI₂, which act as vasodilators, promoting renin release under hypoxic or low-pressure conditions.
