Gonadectomy-induced reduction of antihypertensive action of angiotensin converting enzyme inhibitor and its role of central renin activity in spontaneously hypertensive rats]

Gonadectomy induced a significant retardation of systolic blood pressure (BP) in male and female spontaneously hypertensive rats (SHR). Captopril (5 mg/kg, i.p.), an angiotensin converting enzyme (ACE) inhibitor, significantly decreased BP in all groups, except that the antihypertensive action was significantly inhibited by gonadectomy in both sexes. The plasma ACE activity was increased in orchiectomized males, but this effect did not appear in females. Neither plasma renin activity nor its concentration were changed by gonadectomy in either sex. Aorta ACE activity was not changed by gonadectomy in either sex, while the renin activity was increased only in gonadectomized females. Diencephalon ACE activity was not changed by gonadectomy in either sex, but the renin activity was decreased in these groups. These results suggested that the decrease of BP by gonadectomy in both sexes SHR was closely related to the decrease of renin activity in diencephalon by androgen deprivation with gonadectomy.