hRLX-1. In vitro response of human and pig myometrium.

OBJECTIVE

To study the effect of synthetic h RLX-1 peptide on human and 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. Muscle activity was recorded isometrically in response to varying doses of h RLX-1.

RESULTS

Synthetic h RLX-1 peptide at 0.13 micrograms/mL caused sustained and complete inhibition of pregnant pig myometrial contractility, comparable to that produced by the h RLX-2 peptide, showing, for the first time, its biologic activity in this system. However, a range of concentrations of h RLX-1 peptide (0.07-7.32 micrograms/mL) had no effect on human myometrial contractions in vitro, whereas h RLX-2 peptide had some, albeit minimal, activity in this system.

CONCLUSION

This result 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 relaxins, the human relaxin receptor might. Thus, the control of spontaneous myometrial activity during pregnancy in the human appears to be different from that in other species.