Effect of angiotensin II on in vivo and in vitro release of anterior pituitary hormones in the female rat.

Abstract

Ovariectomized female rats bearing implanted third ventricular cannulae were injected with 2 μl 0.9% NaCl or 2 μl saline containing 5 μg Angiotensin II (AII) or 25 μg saralasin, an AII antagonist. Plasma PRL, GH, LH, and TSH levels were measured by RIA in jugular blood samples drawn through indwelling silastic cannulae while the animals were conscious and freely moving in their cages. Third ventricular injections of AII depressed both PRL and GH levels within 15 min of drug administration, with levels remaining suppressed for up to 1 h. Pretreatment of animals with saralasin slightly elevated basal PRL levels and completely blocked both the PRL- and GH-lowering effects of AII Concentrations of LH and TSH in plasma were not altered by intraventricular AII compared to those of saline-injected control animals. Saralasin alone, on the other hand, decreased plasma TSH levels. Intravenous injection of AII (5 μg/100 μ saline) produced a rise within 5 min in PRL levels, followed by a progressive decline thereafte...