Effect of calcium ion channel antagonists on chorionic gonadotropin secretion

Abstract

By using calcium ion channel antagonists such as Verapamil and Nifedipine, we demonstrated that calcium ion channels are involved in human chorionie gonadotropin (hCG) secretion stimulated by gonadotropin releasing hormone (GnRH). Addition of 1 μM Verapamil (Class II inhibitor) resulted in an inhibition of GnRH-stimulated hCG secretion by placenta without affecting basal release. However, while addition of 10 μM Niffedipine (Class I inhibitor) resulted only in partial inhibition, significant inhibition was observed at 100 μM concentration and above. These results suggest that calcium ion channels in placenta appear to be similar although not identical with the channels reported in the pituitary.