[Effect of insulin and beta-adrenergic blockaders on coronary circulation in response to hypoxia]

An experimental study in dogs with intact thoracic cavity under morphine-chloralose narcosis featured coronary catheterization, extracorporeal perfusion and resistography as well as catheterization of the heart cavities and the coronary sinus. Hemodynamic and respiratory parameters were recorded simultaneously. PO2, PCO2 and pH were measured in the inflowing and outflowing blood. The effect of insulin on circulatory response in acute hypoxic hypoxia was examined before and after obsidan block of beta-adrenoreactive systems. Insulin administered after the obsidan beta-adrenergic block was found to limit coronary dilatation and reduce myocardial oxygen consumption in a more pronounced measure. It is suggested that the effect of insulin on coronary dilatation is due to reduced myocardial oxygen consumption resulting from its action on the heart's beta-adrenergic systems.