Effect of Cis- and Trans-Clomiphene on the Uterine Blood Flow of Oophorectomized Ewes

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Abstract
Changes in the left uterine artery blood flow (UBF) after intraarterial administration of estradiol-17β 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-17β but at dose levels 20 times greater. Comparison of UBF response curves for cis-clomiphene with those for estradiol-17β 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-17β. Similar responses were observed with trans-clomiphene but at dose levels at least 1,000 times those of estradiol-17β. The characteristics of clomiphene-induced UBF responses that differed from those after estradiol-17β may reflect differences in estrogen receptor activation between the compounds.