Uridine: a marker of myocardial viability after coronary occlusion and reperfusion

Tissue accumulation of radiolabeled uridine, a precursor of uracil, reflects ribonucleic acid (RNA) synthesis and may be a marker of viability. To test this hypothesis, myocardial accumulation of H-3 uridine was compared to deoxyglucose uptake and histopathology in an experimental model of myocardial ischemia. In 18 Wistar rats the left coronary artery was occluded for 5, 10 or 60 minutes followed by reperfusion. Five hours later H-3 uridine and C-14 deoxyglucose were administered intravenously and the animals were sacrificed 45 minutes later. The left ventricle of each animal was divided into 12 segments and myocardial tracer accumulation was determined by measurement of tissue radioactivity. From the results of TTC staining, the animals were divided into 3 groups: Group I--ischemia without infarction (n = 9); Group II--non-transmural infarction (n = 4) and transmural infarction (n = 5). Retention of uridine was observed in ischemic zones with enhanced deoxyglucose accumulation in Group I animals. Uridine accumulation was relatively preserved compared to slightly decreased deoxyglucose accumulation in regions of non-transmural infarction in Group II. In Group III, uridine accumulation decreased in parallel with deoxyglucose in zones of infarction. These result suggest that accumulation of radiolabeled uridine may be a useful indicator of viability in ischemic myocardium.