Elements of a paracrine tubular renin-angiotensin system along the entire nephron

The renin-angiotensin system is a major regulator of body sodium, predomina ntly through the actions of intrarenal angiotensin II of unclear origin. We show that polarized epithelium of the proximal tubule synthesizes and secr etes angiotensinogen at its apical side and that the protein can be detecte d in urine as a function of dietary sodium, Furthermore, we demonstrate tha t renin is expressed and secreted in a restricted nephron segment, the conn ecting tubule, also in a sodium-dependent fashion. A paracrine renin-angiot ensin system operating along the entire nephron may contribute to long-term arterial pressure regulation by integrating distant tubular sodium-reabsor bing functions.