Localization of components of the renin-angiotensin system within the kidney.
Evidence accumulates that intrarenal angiotensin II (AngII) plays important roles in the regulation of renal functions. To determine the mechanism and site of the intrarenal formation of AngII, we employed histochemical and cell biological methods. Immunohistochemical studies have revealed the coexistence of renin and AngII 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 this AngII accumulation has been investigated. Immunoreactive angiotensin I (AngI) appeared slowly in JG cells after prolonged administration of angiotensin-converting enzyme (ACE) inhibitors. Cloned and cultured renin-containing cells derived from rat kidney were also found to contain renin, ACE, and AngI and AngII. The subcellular fractionation of renin granules from rat kidney homogenate demonstrated AngI and AngII in the renin granule fractions. These findings suggest the formation of both angiotensins in JG cells. To study the release of AngII, we determined the presence of the angiotensins in renal lymph. Renin was found in renal lymph at a high concentration. Both AngI and AngII were also present in renal lymph in moderate concentrations. It is possible that AngII in the interstitial fluid may play a role in the regulation of renal functions. From these results it has been concluded that AngII is formed in JG cells in the kidney and is secreted with renin into interstitial fluid and plasma, and that AngII formed in the kidney cells may participate in various renal functions.
D000804:Angiotensin II / Q000502:physiology; D000818:Animals; D002478:Cells, Cultured; D003594:Cytoplasmic Granules / Q000502:physiology / Q000648:ultrastructure; D007606:Juxtaglomerular Apparatus / Q000502:physiology / Q000648:ultrastructure; D007668:Kidney / Q000502:physiology* / Q000648:ultrastructure; D008196:Lymph / Q000502:physiology; D051381:Rats; D012083:Renin / Q000502:physiology; D012084:Renin-Angiotensin System
D000804:Angiotensin II; D012083:Renin