ANP and urodilatin: who is who in the kidney.

Mounting evidence suggests that urodilatin, not atrial natriuretic peptide (ANP) is the responsible peptide in regulation of renal Na superset+- and water homeostasis. Following the discovery of ANP this peptide was thought to be responsible for the induction of natriuresis and diuresis in the mammalian kidney. However, the isolation of urodilatin from human urine and substantial work contributed to a better understanding of the renal physiology of these two natriuretic peptides. Indeed, subsequent elucidation supported that urodilatin rather than ANP seems to be the natriuretic peptide responsible for the regulation of Na superset+- and water homeostasis in the kidney. Urodilatin - synthesized and secreted from the distal tubules of the kidney - may act as a paracrine mediator when secreted into the lumen. In contrast, while the role of ANP as regulator of the cardiovascular system is established, its physiological regulatory role on transport processes in the nephron is questionable. This review attempts to analyze the roles of both ANP and urodilatin and to discuss new potential candidates which may also play a role in electrolyte and water handling in the kidney.