Effects of Cis- and trans-clomiphene on the uterine blood flow of oophorectomized ewes.

Changes in the left uterine artery blood flow (YBF) after intraarterial administration of estradiol-17beta and cis- and trans-clomiphene citrate to conscious, oophorectomized ewes were monitored by chronically implanted electromagnetic flow probes. Cis-clomiphene produced UBF increases comparable to or greater than those produced by estradiol-17beta but at dose levels 20 times greater. Comparison of UBF response curves for cis-clomiphene with those for estradiol-17beta showed a delayed onset of initial vasodilation and a delayed peak response. The duration of uterine vasodilation produced by cis-clomiphene was dose-dependent and exceeded that produced by estradiol-17beta. Similar reponses were observed with trans-clomiphene but at dose levels at least 1,000 times those of estradiol-17beta. The characteristics of clomiphene-induced UBF responses that differed from those after estradiol-17beta may reflect differences in estrogen receptor activation between the compounds.