Stimulatory or inhibitory effects of angiotensin II upon LH secretion in ovariectomized rats: a function of gonadal steroids.

The effects of intraventricular infusions of artificial cerebrospinal fluid (aCSF) or angiotensin II (AII) on LH secretion were investigated in rats that had been ovariectomized for 8 days. In untreated ovariectomized rats, the mean whole blood concentration of LH as well as the amplitude, frequency, and nadir of the LH pulses were not affected by infusion of aCSF or 15 ng AII/h, but were suppressed in a dose-dependent fashion by infusion of AII at doses of 150 or 600 ng/h. The AII receptor antagonist, saralasin, blocked the inhibitory effect of AII, demonstrating the specificity of the response to AII. In ovariectomized rats pretreated with estradiol, infusion of AII did not modify mean blood LH levels. However, in ovariectomized rats pretreated with both estradiol and progesterone, infusions of AII at 150 or 600 ng/h produced dose-dependent increases in mean LH concentrations. The results demonstrate both inhibitory and stimulatory effects of AII upon LH secretion, the direction of the effect being determined by gonadal steroids.