Effect of vasoactive intestinal polypeptide on the canine cardiovascular system

Our purpose was to determine the effect of vasoactive intestinal polypeptide (VIP) on the cardiovascular system with special emphasis on coronary vascular effects. In section I, VIP was infused into six healthy and six cobalt-cardiomyopathic dogs at two infusion rates (0.02 and 0.05 micrograms/kg/min). Left ventricular end diastolic pressure and mean systemic pressure fell significantly in both groups. Heart rate rose in both, and maximum systolic dP/dt increased in the myopathic group. Cardiac output and regional blood flows were determined by serial left atrial injections of radioactive 15 +/- 3 mum (mean +/- SD) microspheres. In both groups, blood flow increased significantly to the esophagus, pancreas, atria, and ventricles and to the endocardial and epicardial regions of the left ventricular free wall. Blood flow to the brain decreased. In section II, VIP was infused intravenously at 0.1 micrograms/kg/min into six anesthetized dogs with coronary sinus flow, pulmonary artery, and systemic artery catheters inserted. Cardiac index rose from baseline (3.1 +/- 0.5 to 4.8 +/- 1.3 L/min/m2, P less than 0.005), as did coronary blood flow (90 +/- 25 to 159 +/- 54 ml/min, P less than 0.005) during the VIP infusion. Myocardial oxygen consumption rose from 14.1 +/- 3.9 to 19.8 +/- 5.4 ml/min (P less than 0.001), but the aorta-to-coronary sinus O2 difference decreased from 157 +/- 19 ml/L to 132 +/- 42 ml/L (P less than 0.05), and the percent O2 extracted from coronary blood also decreased significantly.(ABSTRACT TRUNCATED AT 250 WORDS)