The renal proximal tubule renin-angiotensin system.

In conclusion, a complete RAS is present in the mammalian proximal tubule that is potentially autocrine and paracrine in nature. Maneuvers that stimulate renin in JG cells and renal vasculature appear to also stimulate renin in the proximal tubule. The subcellular localization of the different components and the regulation of this epithelial RAS still remain to be defined. This RAS may be important in regulation of proximal tubule NaCl and NaHCO3 transport. Finally, one can speculate that activation of this RAS may play a pathogenetic role in some patients with essential hypertension and in the hypertension and cyst growth seen in autosomal dominant polycystic kidney disease.