Expression of endothelin receptors in human myometrium during pregnancy and in uterine leiomyomas.

The distribution of mRNAs for endothelin A and B (ETA and ET B ) receptors and their binding properties was studied in human nonpregnant and pregnant term myometrium and in uterine leiomyomas. ET A - and ET B -receptors functionally coupled to phospholipase C (PLC) coexisted in myometrial tissues, but only the functional ET A -receptor subtype was detected in leiomyomas. ETA-receptor mRNA and three other spliced variants were distributed in all tissue studied. We reported an increase in the proportion of ETA-receptors coupled to PLC in term pregnant myometrium when compared to nonpregnant tissue. These results suggest that upregulation of the myometrial ET A -receptors may account for or contribute to the control of normal development and growth of human myometrium during pregnancy. They also support a pathological role for the endothelin-1 (ET-1)/ET A -receptor system in leiomyoma development.