ADENOSINE REGULATES CORONARY BLOOD-FLOW DURING INCREASED WORK AND DECREASED SUPPLY

Adenosine may mediate coronary vasodilation during work-related hypere mia and during ischemia. We tested whether adenosine blockade with 8-p -sulfophenyltheophylline (PSPT) prevented dobutamine-induced hyperemia or magnified the reductions in flow due to vasopressin. Control (n = 8) and test (n = 7) dogs received paired infusions of dobutamine (70 m ug/min iv for 5 min). Test dogs received PSPT (10 mg/kg iv) between do ses. In both groups, paired infusions elicited comparable increases in oxygen consumption. However, in test dogs, the hyperemia was reduced significantly. Thus adenosine mediates the hyperemia of dobutamine. Se parately, control dogs (n = 9) received vasopressin (0.6 mug ic over 5 min); test dogs (n = 7) received PSPT before vasopressin. Vasopressin maximally increased coronary resistance by 3 min; effects were gone b y 10 min. With PSPT, coronary resistance was increased further and rem ained high beyond 10 min. Thus adenosine-mediated vasodilation moderat es the severity and duration of ischemia. These results indicate the i mportance of adenosine in mediating coronary flow during increased dem and and reduced supply.