Angiotensin II immunoreactivity coexists with renin in the juxtaglomerular granular cells of the kidney.

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Abstract
The multiple physiologic functions of angiotensin II (AII) are generally supposed to be mediated by the peptide generated in the blood circulation. In addition to this extracellular mechanism of AII formation, immunohistochemical evidence was obtained for the intracellular synthesis of AII in the kidney. Rats were perfused with fixative, and paraffin sections of the kidneys were processed with antisera against renin (EC 3.4.99.19), AII and other components of the renin-angiotensin system. Renin immunoreactivity was regularly observed in the epithelioid granular cells in the media of the afferent vessel of the glomerulus. AII immunoreactivity coexisted within the same cells. This observation points to an intracellular production of AII in the juxtaglomerular epithelioid granular cells. AII may then be released concomitantly with renin in the interstitial fluid and in the blood. The paracrine secretion of AII could exert a local regulatory influence on the tonus of the glomerular vessels.