Juxtaglomerular cells as a source of intrarenal angiotensin II production

While the contribution of angiotensin (Ang) II to the regulation of various renal functions is recognized, evidence exists that the kidney also is a major site for the production of Ang II. Since circulating renin in plasma accounts for only a small portion of intrarenally produced Ang II, we investigated juxtaglomerular (JG) cells as a source of Ang I and II. Light and electronmicroscopic immunohistochemical methods revealed highly concentrated Ang I and II in JG cells. This finding was supported by the demonstration of colocalization of renin, Ang I, and Ang II in cultured JG cells and in dense granular fractions of rat kidney separated by gradient centrifugation of rat kidney homogenate. Perfusion of rat kidney with Krebs-Ringer buffer containing bovine serum albumin showed that Ang I and Ang II are released in the perfusate in quantities which may account for a greater part of the intrarenal generation of Ang II observed in vivo. These results support the hypothesis that Ang II is intrarenally synthesized inside the JG cells, thereby contributing to the regulation of certain renal functions.