ObjectiveTo determine if there are endothelia receptors on human uterine leiomyomas.MethodsSamples of leiomyomas from eight patients were analyzed for [iodine (I) -125]endothelin-1 binding. Several subtype-selective ligands were used to determine the endothelia receptor population.ResultsBinding of [125I]endothelin-1 to uterine leiomyoma membranes was specific and saturable, with a mean ± dissociation constant 85.5 ± 8.4 pM. Competition binding studies showed that the order of potency was endothelia-1 > endothelia-3, which was consistent with the presence of the endothelinAreceptor subtype. Binding of [125I]endothelin-1 was displaced by an endothelinA-selective antagonist, but not by sarafotoxin 6c, an endothelinB-selective agonist. An endothelinB-selective ligand was not specifically bound to leiomyoma.ConclusionThese results indicate that only endothelinAreceptors are present in human uterine leiomyomas. We speculate that endothelia-1 may act through these endothelinAreceptors to influence the development or regulation of hypertrophy and proliferation of the human myometrium during pregnancy and in uterine disorders like leiomyomas.