Endothelium-dependent gender differences in the response of the rat aorta

Segments of rat aortic arch were studied to determine the existence of sexual dimorphism. The influence of the endothelium in mediating gender differences in contractility (maximum tension, Tmax) and sensitivity (ED50) to prostaglandin F2 alpha was measured. This was done in both intact and denuded vascular ring preparations which were dissected from adult male and female rats. Group I comprised untreated male and female rats; Groups II and III were treated with testosterone (10 mg/kg i.m.) or 17 beta-estradiol (2.5 mg/kg i.m.), respectively, on days 1, 3 and 6 and sacrificed on day 7. Intact vascular ring preparations from untreated females were significantly less sensitive (P less than .01) and less contractile (P less than .025) than those from the males. After the intimal surface of the aortic arch rings was rubbed the rings from females exhibited a significant increase in Tmax. However, in vessels from males endothelial denudation had no effect on either Tmax or ED50. Testosterone treatment of female rats significantly increased Tmax (P less than .01) and decreased the ED50 (P less than .01) when compared to rings from untreated females. Testosterone treatment did not significantly affect either parameter in vessels from females which had been rubbed. Testosterone treatment also had no significant effect in either intact or rubbed vessels from males. Estrogen treatment significantly increased the Tmax (P less than .05) of intact vessels from females and had no effect on other vessel segments. Thus, the gender difference in Tmax may relate to an attenuating effect of the endothelium on contractility in the rings from females.(ABSTRACT TRUNCATED AT 250 WORDS)