Deuterium oxide reduces agonist and depolarization-induced contraction of rat aortic rings

The influence of deuterium oxide (D2O) on calcium-dependent vascular smooth muscle contraction was investigated. The effect of D2O on receptor-operated calcium channels was investigated with phenylephrine-induced contraction in the rat aortic ring preparation. D2O depressed the contraction response in a dose-dependent manner with 50% inhibition of maximum contraction observed with 60% D2O. The effect of 60% D2O on phenylephrine-induced contraction was reversible and not dependent on an intact endothelium. Sixty percent D2O also reduced potassium chloride induced contractions by 50%, indicating an effect on voltage-operated calcium channels. Studies with Bay K 8644, and L-type calcium channel activator, confirm an effect on utilization of extracellular calcium sources and on the voltage-operated calcium channel. Sixty percent D2O also depressed a calcium contraction dose-response curve by approximately 25%. Likewise, a change in the pD2' for nifedipine in the presence of D2O may indicate an effect on the nifedipine binding site and (or) the voltage-dependent calcium channel. Further studies were performed to determine whether the D2O effects were nonspecific or selective effects on the receptor- and voltage-operated calcium channels. Sucrose-induced contaction in the presence of 60% D2O was found to be inhibited by approximately 50%. D2O similarly affected isoprenaline relaxation, which would suggest a nonspecific D2O effect on the vascular smooth muscle contractile process.