Renin synthesis, storage, and release in the rat: a morphological and biochemical study.

When a marked stimulation of the reninangiotensin system induced in the rat by bilateral adrenalectomy and salt-depletion is abruptly blocked by a 48-hr substitution treatment which desoxycorticosterone acetate (DOCA) and saltload, one observes: 1) an absolute increase of a form of renin revealed only after prior acidification (pH, 2.5) of kidney extract before usual incubation at the optimum pH of 6.5 and 2) the simultaneous appearance of many granules containing crystalline cores in the epithelioid cells of the juxtaglomerular apparatus. These observations are compatible with the existence of two forms of renal renin and show that after renin-depletion of the kidney, newly synthesized renin is mainly in the acid-activated form. Storage of this renin the epitheloid cells may possibly take the form of secretory granules with crystalline cores. It is speculated that the acid-activated from of renin may be either a renin proenzyme or a protein-bound form.