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

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