Renin cleaves angiotensinogen to angiotensin I. The principal cell type secreting renin is the juxtaglomerular (JG) cell. Three independent signals stimulate renin release. Which signal acts via a Gs-coupled receptor on JG cells that is INHIBITED (not stimulated) by beta-blockers?

• A Low macula densa NaCl delivery activating COX-2/PGE2/EP4 receptor pathway
• B Low stretch of the afferent arteriole detected by baroreceptive mechanosensors
• C Beta-1 adrenoceptor stimulation by renal sympathetic nerves and circulating catecholamines ✓
• D Angiotensin II acting on AT1 receptors on JG cells (negative feedback)

Explanation

JG cells secrete renin in response to three stimuli: (1) beta-1 adrenoceptor stimulation (Gs → cAMP → PKA → renin exocytosis) — this is the neural pathway inhibited by beta-blockers; (2) reduced stretch of the afferent arteriole (intrinsic baroreceptor mechanism); and (3) reduced NaCl delivery to macula densa (paracrine signalling via PGE2/NO). Angiotensin II inhibits renin secretion (negative feedback). Beta-blockers (e.g., atenolol, bisoprolol) reduce renin secretion and are therefore antihypertensive agents with a RAAS-dependent component of action.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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