Hyperplasia of juxtaglomerular cells and renin localization in kidney of normotensive animals given captopril. Electron microscopic and immunohistochemical studies.

Captopril, a competitive inhibitor of angiotensin I-converting enzyme (ACE), is an orally potent antihypertensive agent. Light and electron microscopic studies of th kidneys of mice, rats, and monkeys given large oral doses of captopril for long duration were conducted. All mice and some rats and monkeys developed hyperplasia of the renin-secreting cells which appeared in several layers surrounding the vascular wall of the afferent arterioles. In the electron microscope, these epithelioid cells appeared heavily loaded with aggregates of homogeneous electron dense, osmiophilic amorphous granules filling distended spaces of the endoplasmic reticulum. The Golgi cisterns often included small, sharply outlined triangular or rhomboid osmiophilic granules. The use of specific renin antibodies and the application of the "three-layer bridge technique" for peroxidase-antiperoxidase defined and verified the accumulation of renin in the juxtaglomerular cells. After cessation of dosing, hyperplasia of the juxtaglomerular cells markedly regressed, and there was a significant reduction in the number and size of the renin granules in such cells.