INAGAMI, T., MIZUNO, K., KAWAMURA, M., OKAMURA, T., CLEMENS, DL. and HIGASHIMORI, K. Localization of Components of the Renin-Angiotensin System within the Kidney and Sustained Release of Angiotensins from Isolated and Perfused Kidney. Tohoku J. Exp. Med., 1992, 166 (1), 17-26 We found colocalization of renin, angiotensin (Ang) I and Ang II in juxtaglomerular (JO) cells of the kidney. Coexistence of Ang II in renin granules was demonstrated by electron microscopic immunogold labeling of these components. Coexistence of both Ang I and Ang II in the high density renin storage granules were also demonstrated by gradient centrifugation of renal homogenate. These findings supported the synthesis of Ang I and Ang II in juxtaglomerular cells. Isolated and cultured JO cells showed the synthesis of Ang I, Ang II and renin. Ang I and Ang II were secreted from isolated and perfused rat kidneys at steady rates over 2 hr. Their secretion rates were proportional to that of renin. The rate of Ang II secretion from the kidney was higher than that from the vascular bed. Ang II was also found in renal lymph. These findings indicate that a large amount of Ang II is generated in JO cells by the intracellular action of renin and may play a significant role in the regulation of renal function. angiotensin I; angiotensin II; juxtaglomerular cells; kidney; perfusion; renin granules; renin release

Evidence continues to accumulate regarding the roles that intrarenal angiotensin II (Ang II) plays in the regulation of renal functions. To determine the mechanism and site of the intrarenal formation of Ang II, we employed histochemical, cell biological and physiological methods. Immunohistochemical studies have revealed the coexistence of renin and Ang II in juxtaglomerular (JG) cells, and electron microscopic studies and subcellular organelle fractionation have demonstrated the colocalization of renin and angiotensin in renin granules. The mechanism of the accumulation of Ang II in JG granules has been investigated.