Given below are two statements. One is labelled Assertion (A) and the other is labelled Reason (R).

Assertion (A) : ANF acts as a check on renin-angiotensin mechanism.

Reason(R) : ANF causes sodium retention and thus leads to an increase in blood pressure.

In light of the above statements, choose the correct answer from the options given below.

(A) is true but (R) is false.

ANF functions to oppose the actions of the renin-angiotensin-aldosterone system (RAAS). ANF is released from the atria of the heart in response to increased blood volume and pressure, and it acts to promote vasodilation, increase renal sodium and water excretion (natriuresis), and inhibit the release of renin. These actions collectively counteract the effects of RAAS, which promotes vasoconstriction and sodium and water retention, thereby helping to regulate blood pressure.

ANF decreases in blood pressure. It causes natriuresis (excretion of sodium in the urine), not sodium retention.