Role of the intrarenal renin-angiotensin system in the control of renal function.

IN THIS review article, we will assess the evidence for the presence and the mechanism of the intrarenal renin-angiotensin system acting as a local hormonal system in the control of renal function.First, we will review the evidence for the presence of a renin-angiotensin system in the kidney.Second, using results of our own and other studies, we will develop the concept that the intrarenal renin-angiotensin system acts as a local hormonal system in the control of renal function.Third, we will discuss experimental observations on the intrarenal effects of angiotensin II.Fourth, we will evaluate the evidence for a direct renal tubular action of angiotensin II.Fifth, we will assess the role of the intrarenal renin-angiotensin system in renal autoregulation.Finally, we will speculate on the function of the intrarenal renin-angiotensin system in the regulation of fluid and electrolyte homeostasis in general. Studies of the Localization of the Intrarenal Renin-Angiotensin System Localization of the Site of Renin SecretionIt now is almost universally accepted that the enzyme, renin, is synthesized and stored by specialized cells, the juxtaglomerular cells, of the renal afferent arteriole in intimate contact with the distal tubule (Edelman and Hartroft 1961;Robertson et al, 1965;Cook 1967;Johnston et al., 1973;Silverman and Barajas 1974;Davis and Freeman 1976).The juxtaglomerular cells are thought to be modified smooth muscle cells because they contain bundles of fibrils and attachment bodies similar to those of smooth muscle cells (Latta, 1973).The macula densa consists of an elongated group of columnar