Inhibition of uterine contraction by synthetic parathyroid hormone fragment

The inhibitory effect of synthetic bovine parathyroid hormone fragment bPTH-(1-34)] on rat uterine contraction was studied $\text{in vitro}$. Oxytocin, prostaglandin F_2α and acetylcholine produced log dose-related contraction. The addition of bPTH-(1-34) shifted the dose-response curves of the three agonists to the right. Two doses of bPtH-(1-34) were tested. The higher dose (400 ng/ml) caused a greater inhibition of the agonists than did the lower dose (40 ng/ml). bPTH-(1-34) also inhibited the uterine contraction elicited by electrical stimulation of the tissue. We suggest that bPTH-(1-34) has a non-specific depressing effect on the contractile mechanism of the uterine tissue.