Inhibition of myocardial reactive hyperaemia but not of hypoxic coronary vasodilatation by constant verapamil infusion in the in situ dog heart.

The purpose of the present study was to investigate the changes of characteristic parameters of myocardial reactive hyperaemia that follow coronary artery occlusion for 10 sec and of the coronary vascular response to hypoxia during constant verapamil infusion (0.01 mg. kg-1 X min-1) in anaesthetized open-chest dogs. Reactive hyperaemia was significantly reduced by the specific Ca-antagonist verapamil, while augmentation of coronary blood flow by 100% N2 inhalation for 30 sec was not significantly influenced by the drug. The experimental results indicate that, similar to myocardial cells, verapamil reduces the oxygen requirement of vascular smooth muscle cells as well. The possibility exist that verapamil excludes factor(s) responsible for the disproportional overpayment of flow debt.