Effects of verapamil and nifedipine on human uterine artery "in vitro".

We have studied, in isolated human uterine arteries, the effects of verapamil and nifedipine on the contractions induced by noradrenaline (NA) and KCl in standard Krebs and those produced by CaCl2 and NA added to a free-calcium medium (128.5 mM K+). Both calcium antagonists reduce in a dose-dependent way the contractions induced by NA, KCl and CaCl2. Smaller doses of nifedipine were needed to produce the same inhibitory effects. The maximal doses of calcium antagonists utilized had no effect on the contractions induced by NA when the calcium was removed from the medium. NA, in equal doses, had similar contractile effect whether after incubation with the maximal doses of verapamil and nifedipine or in a calcium-free medium. The inhibitory effects produced by verapamil and nifedipine are only adequately explained by a blockage of the entry of calcium. Other intracellular changes do not seem to play a role in this case.