Nonmetabolically coupled coronary vasodilatation during inosine infusion in dogs

Left ventricular contractile force (LVCF), dP/dt, arteriovenous oxygen difference [(a-v)O2], circumflex blood flow (CBF), and myocardial oxygen consumption (MVo2) were determined in dogs during intravenous infusion of inosine at various rates. LCVF and maximal dP/dt increased progressively with increasing infusion rates. CBF increased by 100% at the highest infusion rate, but (a-v)O2 was reduced by 30%. At each infusion rate the increase in MVo2 was only 40% the increase in CBF (P less than 0.05), indicating a nonmetabolically coupled vasodilatation. To further demonstrate this action, the effects of isoproterenol on CBF and (a-v)O2 were compared with those of inosine. During isoproterenol infusion, the increase in CB paralleled the increase in MVo2, and (a-v)O2 showed no change. Intracoronary infusion experiments showed that a 100% increase in flow was caused by an arterial inosine level of about 150 micro M. At inosine levels over 400 micro M, the increase in flow was equal to the maximal increase seen with adenosine infusion.