Renin is released by which specialized apparatus in the kidney?

• A. Juxtaglomerular apparatus (juxtaglomerular cells of the afferent arteriole)
• B. Glomerular capillary endothelium
• C. Macula densa cells of the distal convoluted tubule as the primary source of renin
• D. Podocytes of the visceral layer of Bowman's capsule

Answer: (A)

Verified step by step guidance

1. Understand that renin is an enzyme secreted by specialized cells in the kidney that play a key role in regulating blood pressure and fluid balance.
2. Identify the juxtaglomerular apparatus (JGA) as a specialized structure located near the glomerulus, where the afferent arteriole enters the nephron.
3. Recognize that the juxtaglomerular cells, which are modified smooth muscle cells in the wall of the afferent arteriole, are the primary source of renin secretion.
4. Note that while the macula densa cells of the distal convoluted tubule are involved in sensing sodium concentration and signaling the JGA, they do not secrete renin themselves.
5. Understand that other structures like the glomerular capillary endothelium and podocytes of Bowman's capsule do not produce renin.