THE EFFECT OF ANGIOTENSIN-II RECEPTOR ANTAGONISTS ON DIETHYLSTILBESTROL-INDUCED VASCULAR CHANGES IN THE RAT ANTERIOR-PITUITARY GLAND - A QUANTITATIVE-EVALUATION

The effects if diethylstilbestrol (DES) and of angiotensin II (Ang II) receptor antagonists, such as losartan (selective AT(1) receptor anta gonist) or PD 123319 (selective AT(2) receptor antagonist) on the ante rior pituitary microvasculature were studied by means of computer-assi sted image analysis. The vascularization was visualized using Selye's method modified by Poely et al. (1964). It was found that DES induced a sharp increase in vessel area, mean vessel diameter and perimeter, w hereas mean vessel number was reduced. These DES-induced changes were inhibited by simultaneous administration of losartan. On the other han d, PD 123319 was less effective. These findings suggest an involvement of Ang II, acting mainly via AT(1) receptors, in the mechanism of est rogen-induced vascular changes in the rat anterior pituitary gland.