Endothelin--a potent constrictor of small myometrial arteries of term pregnant women.

This study was performed to evaluate the in vitro effects of a new polypeptide, endothelin-1 (ET-1) on small intramyometrial vessels in comparison with the action of noradrenalin (NA). In connection with cesarean section, myometrial biopsies were obtained and small arteries (100-500 microns in diameter) were excised. Cylindrical segments of these vessels were used for registration of contractile activity after administration of ET-1 and NA. ET produced vasoconstriction and was approximately three times as powerful and 70-fold as potent as NA. It is suggested that ET may be involved in the regulation of human utero-placental blood flow.