Coexistence of renin and angiotensin II in epitheloid cell secretory granules of rat kidney.

The distribution of renin and angiotensin II (ANG II) in juxtaglomerular epitheloid cells of control and adrenalectomized rats was studied, using specific antisera and the protein A-gold technique in Lowicryl- and glycol methacrylate-embedded tissue. The matrix of virtually all mature secretory granules of epitheloid cells contains not only renin, but also ANG II. On adrenalectomy, the concentration of both renin and On adrenalectomy, the concentration of both renin and ANG II in the granule internum increases markedly, as indicated by the density of the immunolabel. Given the coexistence of renin and ANG II in the granule matrix, it is quite probable that, with each secretory event, a certain amount of ANG II is released together with renin. Further experiments will have to show if this amount of ANG II cosecreted with renin is sufficient to elicit immediate local intrarenal actions. ANG I, as well as angiotensinogen and converting enzyme, were not found in epitheloid cells. It is therefore inferred that ANG II is not generated intracellularly, but within the extracellular space and subsequently taken up by pinocytosis and incorporated into the secretory granules of epitheloid cells.