Effect of parathyroid hormone-related peptide on human and rat myometrial contractility in vitro

OBJECTIVES: The aims of this study were primarily to investigate the effects of parathyroid hormone-related peptide (human fragment 1-34) on human nonpregnant and pregnant (nonlabor and labor) myometrial contractility in vitro and secondarily to compare these effects with those of parathyroid hormone-related peptide on rat myometrial contractility.STUDY DESIGN: Isometric tension recording was performed under physiologic conditions in isolated myometrial strips obtained at hysterectomy and cesarean delivery and from Sprague-Dawley rats. The effect of cumulative additions of parathyroid hormone-related peptide (1, 10, and 100 nmol L) on myometrial contractility was measured and the significance of results was assessed by 2-way analysis of variance.RESULTS: Parathyroid hormone-related peptide exerted a statistically significant net relaxant effect on myometrial contractility in human nonpregnant myometrium (34.71%; P .05) the onset of labor, and in rat tissue (31.60%; P .01).CONCLUSIONS: Parathyroid hormone-related peptide exerts a relaxant effect on human and rat myometrial tissue. In human myometrium, sensitivity to parathyroid hormone-related peptide is reduced in pregnancy and abolished by the onset of labor.