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

Various studies have shown vasorelaxation properties for 17alpha- and 17beta-oestradiol. Here, we studied the effects of gender difference as well as oestrous cycle on oestradiol-induced vasorelaxation in mesenteric arteries from male and female guinea-pigs and in main uterine arteries from female guinea-pigs in vitro. Both 17alpha- and 17beta-oestradiol (0.5-20 micromol L-1) induced concentration-dependent relaxation of both mesenteric and uterine arteries preconstricted with either noradrenaline (NA; 10 micromol L-1) or KCl (125 mmol L-1) from both day-7 and day-15 female guinea-pigs. 17beta-oestradiol was more potent in relaxing arteries precontracted with NA than those pretreated with KCl, while 17alpha-oestradiol was more effective in relaxing those arteries precontracted with KCl. In mesenteric arteries from male animals, 17alpha-oestradiol was significantly (P < 0.001) more potent on arteries precontracted with NA than KCl, an effect opposite to that seen on arteries from female animals. However, both 17alpha- and 17beta-oestradiol were more potent in relaxing arteries from male animals compared with their female counterparts. These data indicate a possible role for gender differences in the vascular effects of oestradiols.