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 effect s of parathyroid hormone-related peptide (human fragment 1-34) on human non pregnant and pregnant (nonlabor and labor) myometrial contractility in vitr o and secondarily to compare these effects with those of parathyroid hormon e-related peptide on rat myometrial contractility. STUDY DESIGN: Isometric tension recording was performed under physiologic c onditions in isolated myometrial strips obtained at hysterectomy and cesare an delivery and from Sprague-Dawley rats. The effect of cumulative addition s of parathyroid hormone-related peptide (1, 10, and 100 nmol/L) on myometr ial contractility was measured and the significance of results was assessed by 2-way analysis of variance. RESULTS: Parathyroid hormone-related peptide exerted a statistically signif icant net relaxant effect on myometrial contractility in human nonpregnant myometrium (34.71%; P <.01), in human pregnant myometrium obtained before ( 18.27%; P <.05) but not after (10.32%; P >.05) the onset of labor, and in r at tissue (31.60%; P <.01). CONCLUSIONS: Parathyroid hormone-related peptide exerts a relaxant effect o n human and rat myometrial tissue. In human myometrium, sensitivity to para thyroid hormone-related peptide is reduced in pregnancy and abolished by th e onset of labor.