Which statement best describes the effects of ANP and BNP on blood pressure and blood volume?

• A. Vasoconstriction and water retention.
• B. Vasodilation and natriuresis.
• C. Decrease GFR.
• D. Increase renin release.

Answer: (B)

ANP and BNP are hormones that respond to increased blood volume and atrial/ventricular stretch, acting to reduce pressure and volume by opposing the systems that raise them. They promote vasodilation, which lowers systemic vascular resistance, and they also promote the excretion of sodium and water (natriuresis and diuresis) by the kidneys. They do this in part by suppressing renin release and reducing aldosterone, which further decreases sodium reabsorption. The combined effect is a drop in both blood pressure and blood volume. So the statement that best fits is that these hormones cause vasodilation and natriuresis. The other options describe actions that would raise blood pressure or volume (vasoconstriction, water retention, or reduced GFR) or increase factors that raise volume (renin), which is not how ANP and BNP work.