Immunoelectron microscopic localization of renin in the juxtaglomerular cells of the amphibian Bufo bufo.

The ultrastructural localization of renin in the juxtaglomerular apparatus of the kidney of the toad Bufo bufo has been examined using an immunogold staining method for electron microscopic immunocytochemistry and an antiserum to renin isolated from the submandibular gland of the mouse. Renin immunoreactivity was confined to lamellated granules in the cytoplasm of epitheloid or juxtaglomerular cells in the glomerular afferent arterioles and also in the media cells of larger arteries. Mouse kidney tissue, examined for purposes of comparison, showed immunolabeling limited to the granules of the juxtaglomerular cells. The presence of renin or a renin-like substance in the juxtaglomerular granules of the toad kidney is discussed in relation to the lysosomal nature of these granules. A model is presented linking the lysosomal function of the juxtaglomerular granules and the release of renin mediated by beta-adrenergic receptors present on the surface of the juxtaglomerular cells.