Pregnancy: Effect of the vascular endothelium on contractions induced by prostaglandin F 2 in isolated pregnant guinea pig uterine artery

Open Access
Publisher Website
Google Scholar
Abstract
The purpose of this study was to examine the influence of endothelium on prostaglandin F2α-mediated contractions in pregnant guinea pig uterine artery. Consequently, the effects of prostaglandin F2α pregnant guinea pig uterine arterial rings with both Intact and denuded endothelium were studied. In vessels with denuded endothelium prostaglandin F2α (0.1–10 μM) induced contraction (pD2 = 6.17) with greater potency than in vessels with intact endothelium (pD2 5.68). NG.Monomethyl (10 μM) did not affect the concentration—response curve for prostaglandin F2α regardless of endothelial condition. In contrast, in both types of preparation, indomethacin (10 μM) increased the maximal response value obtained with prostaglandin F2α but this effect was significantly greater in preparations with intact than In those with denuded endothelium (128.3 versus 206.5%). Moreover, indomethacin shifted the concentra tion-response curve for prostaglandin F2α to the left only in preparations with intact endothelium. The PKA values for prostaglandin F2α itself did not differ between preparations: 5.41 and 5.52 for pregnant guinea pig uterine artery with and without endotheliuin, respectively. The receptor reserve expressed as KA/EC50 was significantly greater in rings with denuded (4.44) compared to those In rings with intact endo thelium (1.86). We conclude that prostaglandin-F2α contraction in pregnant guinea pig uterine artery is modu lated by the vascular endothelium. It is probable that cyclo oxygenase products relating to vasodilatation and derived from endothelium mediate this effect, acting as a functional endogenous antagonist and thereby reducing the apparent efficacy and potency of prostaglandin F2α