Renin in adrenal: an overview of its synthesis, subcellular localization, and functions

Specific renin has been identified in the outer layers of the adrenal of rat, mouse and human. Nephrectomy causes a marked elevation of adrenal renin, presumably through hyperkalemia. The subcellular distribution of adrenal renin was investigated by Percoll density gradient. The renin activity in the dense granules from the capsules of nephrectomized rats was 15 times greater than that of intact rats. Most of the active form renin was found in the dense renin granules. Immunohistochemical studies revealed that the dense granules increased in number after bilateral nephrectomy. Immunogold staining of these granules showed unequivocally the presence of renin therein. Adrenal capsules in organ culture were found to release renin at a steady rate. Renin release from bilaterally nephrectomized rat adrenals was 4.6 times greater than from the organs of intact animals. Further, adrenal slices from human adrenocortical tumor tissues which contained specific renin in a sizable quantity were found to release renin in a similar fashion to rats. The mechanism of the control of renin secretion from the adrenal gland was different from the kidney in that the release was stimulated by potassium chloride or angiotensin II but not by ACTH, suggesting stimulation by intracellular calcium. These results provide convincing evidence that the adrenal synthesizes renin, stores it in specific secretory granules, and secretes it in a regulated manner. It is most likely that the adrenal renin plays a role in the production of aldosterone in the adrenal cortex or in the secretion of catecholamines from the adrenal medulla through intra- and/or extracellular formation of angiotensin II.