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 AT1 receptor antagonist) or PD 123319 (selective AT2 receptor antagonist) on the anterior pituitary microvasculature were studied by means of computer-assisted 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, whereas mean vessel number was reduced. These DES-induced changes were inhibited by simultaneous administration of losartan. On the other hand, PD 123319 was less effective. These findings suggest an involvement of Ang II, acting mainly via AT1 receptors, in the mechanism of estrogen-induced vascular changes in the rat anterior pituitary gland.