Influence of bovine parathyroid hormone-(1-34) on the contraction of the rat vas deferens and the effect of calcium

The inhibitory effect of bovine PTH fragment, bPTH-(1-34) on rat vas deferens contraction was studied in vitro. bPTH-(1-34) inhibited the contraction elicited by either electrical stimulation or depolarization with 80 mM K+.Increase of Ca2+ from 2.5 to 5 mM in the medium shifted the dose-response curve of bPTH-(1-34)to the right. In addition, bPTH-(1-34), similar to La3+ and Mn2+, delayed the development of tension induced by Ca2+. bPTH-(1-34) reduced the Ca2+ content in rat vas deferens incubated with 45 CaCl2 for 3 or 5 min. Similar to LaCl3, MnCl2 and verapamil, bPTH-(1-34) influenced the contraction of rat vas deferens induced by Ca2+ in depolarizing high K+ solution. We suggest that the inhibitory effect of bPTH-(1-34) on the contraction of rat vas deferens is acted by interfering with the Ca2+-dependent process of smooth muscle contraction.