Parathyroid hormone-related peptide inhibits oxytocin-induced rat uterine contractionsin vitro

Abstract

Synthetic human parathyroid hormone-related peptide (hPTHrP)-(1-34) fragment was compared with parathyroid hormone (bovine sequence, 1-34; bPTH-(1-34) for inhibiting oxytocin or prostaglandin F2α (PGF2α)-induced contractions on rat uterus in vitro. bPTH exhibited a potent (ED₅₀ = 7 × 10⁻⁹M) inhibition on oxytocin-induced contractions. Both bPTH-(1-34) and hPTHrP-(1-34) were devoided of any significant effect upon PGF2α-induced uterine contractions. Human PTHrP also inhibited oxytocin-induced uterine contractions (ED₅₀ = 77 × 10⁻⁹M) and this effect, like that of bPTH, was dose dependent. Human PTHrP-(140-173) fragment had no significant effect on oxytocin-induced uterine contractions. The inhibitory effect of hPTHrP-(1-34) disappeared after pretreatment with [Tyr]³⁴-bPTH-(7-34)-NH₂, a competitive reversible antagonist of bPTH-(1-34). Thus PTHrP might be involved in the control of myometrial activity.