What effect does B-type natriuretic protein have on the kidneys?

B-type natriuretic peptide (BNP) is a hormone produced primarily by the heart's ventricles in response to stretching and increased pressure, which often occurs in heart failure and other cardiac conditions. One of the key roles of BNP is to promote natriuresis, which is the excretion of sodium through the urine. This process leads to an increase in water excretion as well, as water follows sodium osmotically.

By stimulating the kidneys to excrete sodium and water, BNP helps to reduce blood volume and pressure, counteracting the effects of conditions associated with fluid overload, such as congestive heart failure. This diuretic effect contributes to the regulation of blood pressure and fluid balance in the body. Thus, the correct answer accurately reflects the primary renal effect of B-type natriuretic protein, emphasizing its role in promoting sodium and water excretion.