Gonadotropin-Releasing Hormone Receptor Expression in Xenopus Oocytes

The rodent GnRH receptor was characterized in Xenopus oocytes injected with RNA isolated from rat pituitary and from a gonadotrope cell line, αT3, derived from a transgenic mouse. Three to 4 days after 150–200 ng RNA injection, 93% of the oocytes, which were recorded by voltage clamp, responded to 10−7 m GnRH. The mean inward currents obtained after RNA injection were 620 ± 88 nA (n = 22) with pituitary RNA and 1415 ± 598 (n = 4) with αT3 RNA. The threshold GnRH concentration able to evoke the dose dependent current after pituitary RNA injection was 3 × 10−9 m GnRH. The GnRH receptor response of the oocyte was antagonized by [d-Phe2,6,Pro3] GnRH and [N-Ac-d-Na](2)1, d-αd-Me, pCI-Phe2, dArg6, d-Ala10-NH2]GnRH and could be elicited by d-Ser(But)6,Pro9-N-ethylamide GnRH (buserelin). The reversal potential of the GnRH generated current as determined by voltage-ramp was −22.5 ± 1.0 mV (n = 7) and −25.6 ± 3.3 mV (n = 3) in pituitary and cell line RNA-injected oocytes respectively, consistent with the chloride r...