Functional expression of human myometrial endothelin receptors in Xenopus laevis oocytes

We demonstrate the existence of functional endothelin receptors in human uterine myometrium using the Xenopus oocyte expression system. Fifty nanograms of poly(A)+RNA from myometrium was injected into Xenopus laevis oocytes and incubated for 70-80 h. The membrane potential of the oocyte was clamped at -60 mV and membrane current was measured during and after endothelin stimulation. Endothelin-1 elicited a large inward membrane current in the oocytes injected with poly(A)+RNA; endothelin-2 elicited a small current; while endothelin-3 did not induce any membrane current. These results indicate the existence of messenger RNA encoding functional endothelin-1 receptors in human uterine myometrium.