Question

Atrial natriuretic peptide performs all the following functions except -------------------.

• A. Inhibits \(\text{Na}^{+}\) and \(\text{Cl}^{-}\) absorption from collecting ducts.
• B. Decreases excretion of \(\text{Na}^{+}\) in urine.
• C. Inhibits release of renin.
• D. Reduces aldosterone and ADH release.

Hint:

ANP lowers blood volume and pressure by increasing sodium excretion, so it cannot decrease sodium excretion.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept
Atrial natriuretic peptide (ANP) is released by atrial walls when blood volume or pressure is high.

Step 2: Actions of ANP
It inhibits renin release and reduces aldosterone and ADH release.
It blocks sodium and chloride absorption in the collecting ducts.

Step 3: Net effect
More sodium and water leave in urine (natriuresis), which lowers blood volume and pressure.

Step 4: Conclusion
Decreasing sodium excretion is not a function of ANP.

Final Answer:
ANP does not decrease sodium excretion; it increases it. \[ \boxed{\text{(B) }\text{Decreases excretion of Na}^{+}\text{ in urine.}} \]