Mechanisms by which intrarenal dopamine and ANP interact to regulate sodium metabolism.

Maintenance of a normal blood pressure requires a precise and fine-tuned regulation of salt metabolism. This is accomplished by a bidirectional regulation of renal tubular sodium transporters by natriuretic and antinatriuretic hormones. Dopamine, produced in the renal proximal tubular cells, plays an important role in this interactive system. Dopamine inhibits the activity of Na+,K+ ATPase as well as of many important sodium influx pathways in the nephron. These effects of dopamine are particularly pronounced in situation of sodium loading. There is an abundance of evidence suggesting that the natriuretic effects of ANP are to a large extent mediated via renal dopamine 1 like receptors. The renal tubular dopamine 1 like receptors are, under basal conditions, mainly located intracellularly. ANP and its second messenger, cGMP, cause a rapid translocation of the dopamine 1 like receptors to the plasma membrane. This phenomenon may explain how ANP and dopamine act in concert to regulate sodium metabolism. Regulation of sodium metabolism and blood pressure is critically dependent on a normal function of the renal dopamine system. Hence, abnormalities in the interaction between dopamine and ANP may predispose to hypertension.