A stereological study of the trophic effects of the renin-angiotensin system on the rat adrenal zona glomerulosa.

Left renal artery stenosis increased and timolol maleate chronic administration decreased systolic blood pressure, plasma renin activity, and plasma aldosterone concentration, in adult male rats. In the hypertensive animals the volume of the zona glomerulosa, the volume and number of zona glomerulosa cells, as well as the volume of the mitochondrial compartment and the surface area of SER and mitochondrial cristae, were significantly increased. The volume of the lipid compartment was reduced, and several clumps of electron-dense granules appeared at the juxta-sinusoidal pole of the cells. Opposite results were found in the zona glomerulosa of the hypotensive rats, with the exception that the volume of the lipid compartment showed no significant change. These findings suggest that the renin-angiotensin system is involved in the maintenance and stimulation of the growth in the zona glomerulosa. Since in the hypertensive rats the increase in the volume density of electron-dense granules fits well with that in the intracellular concentration of aldosterone, the working hypothesis is that these granules are aldosterone-containing secretory organelles.