Question

Renin is released from:

• A. \( \text{Hepatocytes of liver} \)
• B. \( \text{Beta-cells of pancreas} \)
• C. \( \text{Microglial cells} \)
• D. \( \text{Juxtaglomerular cells (JGCs) of kidney} \)

Hint:

The juxtaglomerular cells of the kidney release renin in response to: 1. Low blood pressure. 2. Low sodium concentration in the distal tubule. 3. Activation of the sympathetic nervous system. This is a key component of the renin-angiotensin-aldosterone system (RAAS).

Answer 1

The Correct Option is D

Step 1: Understanding the renin-angiotensin system. Renin is an enzyme secreted by the juxtaglomerular cells (JGCs) of the kidney in response to decreased blood pressure, reduced sodium levels, or sympathetic nervous system activation. It plays a vital role in regulating blood pressure and fluid balance. Step 2: Mechanism of renin release. Renin converts angiotensinogen (produced by the liver) into angiotensin I, which is then converted into angiotensin II by angiotensin-converting enzyme (ACE). Angiotensin II causes vasoconstriction and stimulates aldosterone secretion, increasing blood pressure. Step 3: Comparison with other options. - Option \( (A) \): Hepatocytes of the liver produce angiotensinogen, not renin. - Option \( (B) \): Beta-cells of the pancreas secrete insulin, not renin. - Option \( (C) \): Microglial cells are involved in immune functions in the central nervous system. Conclusion: Renin is specifically released by the juxtaglomerular cells (JGCs) of the kidney, making \( (D) \) the correct answer.

Answer 2

This question tests where in the body renin is produced. The clue is in the hormone's job: it starts the renin-angiotensin-aldosterone pathway that controls blood pressure, so the source cell type should sit somewhere that can sense blood pressure and salt levels directly. Let's check each option against that clue.

1. Hepatocytes of liver: Liver cells make angiotensinogen, the inactive protein that renin later acts on. Making the substrate is not the same as making the enzyme, so this cannot be the renin source.
2. Beta-cells of pancreas: These cells make and release insulin in response to blood glucose. They have no role in blood pressure sensing or renin production.
3. Microglial cells: These are immune cells living in the brain and spinal cord, involved in defense against infection and injury there. They sit far outside the kidney's blood pressure control system.
4. Juxtaglomerular cells (JGCs) of kidney: These specialized smooth muscle like cells sit in the walls of the afferent arteriole, right next to the glomerulus. Their location lets them sense a drop in blood pressure or a fall in sodium delivery directly, and in response they release renin into the blood.

Only the juxtaglomerular cells are positioned to sense blood pressure changes and respond by secreting renin.

Therefore, the correct answer is Juxtaglomerular cells (JGCs) of kidney.