Vasorelaxant effects of oestradiols on guinea pigs: a role for gender differences

Background Various studies have shown vasorelaxation properties for 17 alph a- and 17 beta -oestradiol. Material and methods Here, we studied the effects of gender difference as w ell as oestrous cycle on oestradiol-induced vasorelaxation in mesenteric ar teries from male and female guinea-pigs and in main uterine arteries from f emale guinea-pigs in vitro. Results Both 17 alpha- and 17 beta -oestradiol (0.5-20 mu mol L-1) induced concentration-dependent relaxation of both mesenteric and uterine arteries preconstricted with either noradrenaline (NA; 10 mu mol L-1) or KCl (125 mm ol L-1) from both day-7 and day-15 female guinea-pigs. 17 beta -oestradiol was more potent in relaxing arteries precontracted with NA than those pretr eated with KCl, while 17 alpha -oestradiol was more effective in relaxing t hose arteries precontracted with KCl. In mesenteric arteries from male anim als, 17 alpha -oestradiol was significantly (P < 0.001) more potent on arte ries precontracted with NA than KCl, an effect opposite to that seen on art eries from female animals. However, both 17 alpha- and 17 beta -oestradiol were more potent in relaxing arteries from male animals compared with their female counterparts. Conclusion These data indicate a possible role for gender differences in th e vascular effects of oestradiols.