Effect of inosine on ventricular regional perfusion and infarct size after coronary occlusion

In 16 dogs inosine was infused at 0.5 mmol/min i.v. for 5 min beginning 15 min after coronary occlusion. Tracer microspheres were used to estimate flow in subepicardium and subendocardium of nonischemic, central ischemic, and borderline isch-emic muscle. Estimates of flow before occlusion, 5 min after occlusion, during inosine infusion, 30 min after infusion and 60 min after infusion were obtained. Coronary occlusion reduced flow in the central ischemic regions by 75-95%. The reduction in flow was greatest in subendocardium. In the borderline regions subendocardial flow was reduced by 30% while subepicardial flow was unaffected. The major effects of inosine were seen in non-ischemic and borderline ischemic regions. Flow in borderline subendocardium returned to its pre-occlusion value, and flow in nonischemic myocardium increased by approximately 60-80%. However, only in the ischemic regions was the increase in flow sustained for the entire 60 min. In 20 dogs infarct size was determined using nitro blue tetrazolium stain. In 10 controls infarct size was 20.1%, while in 10 inosine-treated dogs infarct size was 15.2% of left ventricular weight (p <0.01). Thus, following coronary occlusion inosine infusion was associated with an increase in perfusion of ischemic myocardium and a reduction in infarct size.