Angiotensin-converting enzyme labeled with [3H]captopril. Tissue localizations and changes in different models of hypertension in the rat.

In vitro autoradiography with [3H]captopril was used to localize and quantitate angiotensin-converting enzyme (ACE) in various tissues in two-kidney, one-clip (2K-1C) hypertension, one-kidney, one-clip (1K-1C) hypertension, desoxycorticosterone acetate (DOCA)-salt hypertension, and a normotensive control group. There were no significant differences in mean systolic blood pressure among the hypertensive groups. Plasma renin activity (PRA) was highest in the 2K-1C group (6.20 +/- 2.17 ng/ml per h), intermediate in the 1K-1C group (2.19 +/- 0.62 ng/ml per h) and control group (3.20 +/- 0.53 ng/ml per h), and lowest in the DOCA-salt group (0.07 +/- 0.06 ng/ml per h). In the lungs, aorta, mesenteric arteries, and adrenal medulla, ACE labeling was highest in the 2K-1C group, intermediate in the 1K-1C and control groups, and lowest in the DOCA-salt group. ACE levels in these tissues correlated positively with PRA. In the kidney, anterior pituitary, testis, and choroid plexus of the brain, ACE levels correlated negatively with PRA, with lowest ACE levels in the 2K-1C group and highest levels in the DOCA-salt group. In the epididymis, posterior pituitary, and other regions of the brain, ACE levels did not differ significantly among the groups.