Cells Secreting Renin in Kidney

Renin hormone is secreted by which cells of the kidney-

Correct Answer: JG cells

Renin is secreted by JG (Juxtaglomerular) granular cells — modified smooth muscle cells of the afferent arterioles of the glomerulus.

Critical Distinction: Renin vs. Rennin

• Renin: Hormone secreted by JG cells of kidney → converts Angiotensinogen to Angiotensin-I → blood pressure regulation (RAAS)
• Rennin (Chymosin): Enzyme secreted by gastric chief cells of stomach (abomasum in ruminants) → curdles milk (caseinogen → insoluble casein) → important in cheese making and neonatal milk digestion

Triggers for Renin Release

• Decreased blood pressure → detected by JG cells as baroreceptors
• Decreased Na⁺ in tubular fluid → detected by macula densa cells
• Sympathetic activation (β₁ receptor stimulation)

All Three Kidney Hormones

• Renin → blood pressure regulation (RAAS)
• Erythropoietin → stimulates RBC production in bone marrow
• 1,25-Dihydroxycholecalciferol (Calcitriol, active Vitamin D) → increases intestinal Ca²⁺ absorption and bone mineralization