[Endothelin receptors in benign human tumours of uterine muscle]

The endothelins (ET1, ET2, ET3) are a family of peptides that exert vasoactive and mitogenic effects. ETs bind to at least two subtypes of receptors: the ETA subtype is ET1 selective whereas the ETB subtype binds ET1, ET2 and ET3. By RT-PCR, we detected ETA receptor mRNA and ETB receptor mRNA in leiomyoma and in homologous myometrium distal from the tumor. Despite the presence of four spliced variants of ETA receptors, we identified a single class of ETA-binding sites. The level of ETB receptor mRNA was found to be higher in myometrium versus leiomyomas. Using complementary pharmacologic approach, we demonstrated the predominance of ETA receptors in normal myometrium (75% of total receptors). Both ETA and ETB transcripts coexist in leiomyomas, but we have reported only ETA binding sites. Because of growth properties of ET1, we suggest a role for this peptide in the tumoral development of human uterine smooth muscle.