HRLX-1 - IN-VITRO RESPONSE OF HUMAN AND PIG MYOMETRIUM

OBJECTIVE: To study the effect of synthetic h RLX-1 peptide on human a nd porcine myometrium in vitro in comparison to the effect of h RLX-2 peptide. STUDY DESIGN: Myometrial strips from humans and pigs in late pregnancy were allowed to spontaneously contract in an organ bath. Mus cle activity seas recorded isometrically in response to varying doses of h RLX-1. RESULTS: Synthetic h RLX-1 peptide at 0.13 mu g/mL caused sustained and complete inhibition of pregnant pig myometrial contracti lity, comparable to that produced by the h RLX-2 peptide, showing, for the first time, its biologic activity in this system. However, a rang e of concentrations of h RLX-1 peptide (0.07-7.32 mu g/mL) had no effe ct on human myometrial contractions in vitro, whereas h RLX-2 peptide had some, albeit minimal, activity in this system. CONCLUSION: This re sult shows that h RLX-1 peptide does not appear to be an inhibitor of human myometrial activity and that although the pig myometrial relaxin receptor does not appear to distinguish between the two human relaxin s, the human relaxin receptor might. Thus, the control of spontaneous myometrial activity during pregnancy in the human appears to be differ ent from that in other species.