Myocardial high-energy phosphates and function under different postischemic conditions. A study in a paracorporeal rat heart model.

Infusion of phosphoenolpyruvate together with adenosine triphosphate early during reperfusion after ischemia increased the energy content and the left ventricular isovolumic performance in a paracorporeal rat heart model. Excised hearts were subjected to 15 min of complete global ischemia at 37 degrees C before reperfusion. During reperfusion they were either nonworking (empty-beating) or working (performing left ventricular isovolumic work) between 20 and 40 min of reperfusion before freeze-clamping. Early during reperfusion the excised hearts were either supplemented with 144 mumol phosphoenolpyruvate and 0.67 mumol adenosine triphosphate or nonsupplemented (plain saline) administered in a pulsatile arterial blood flow. The supplemented nonworking group showed significantly higher creatine phosphate and adenosine triphosphate contents compared to the nonsupplemented group. However, under postischemic working conditions there were no significant differences in high-energy phosphates between the supplemented and the nonsupplemented groups in spite of significantly better left ventricular isovolumic performance in the supplemented group. Concomitantly the efflux of creatine kinase isoenzyme MB indicating cellular damage was significantly less for this group. The data presented here favor the view of a possible compartmentalized adenosine triphosphate pool with a high metabolic turnover close to the plasma membrane.