Aim: The precise understanding of myocardial metabolism is crucial for the optimization of cardiosurgical procedures. We attempted to gain a comprehensive insight into the purine metabolism of the porcine heart during reperfusion by measuring concentrations of nucleotides, nucleosides and oxypurines simultaneously in the myocardium and coronary sinus.
Methods: Twenty-five pigs were subjected to sham cardiosurgery with extracorporeal circulation and cold cardioplegic arrest of 60 min. Myocardial biopsies, as well as coronary sinus and arterial blood samples were taken before aortic clamping and at 5, 20, 60 and 120 min of reperfusion. HPLC was used to measure concentrations of 17 purines in the bioptates and of 5 in plasma.
Results: Reperfusion rapidly normalized the ischaemic decrease in the adenylate energy charge of the myocardium, but during 120 min failed to restore the reduced adenylate pool, because of irreversible loss of nucleosides by cardiomyocytes. Low adenylate energy charge and depletion of the adenylate pool were accompanied by analogous changes in the guanylates and growing deficit of NAD and NADP. Reperfusion was marked by significant release of inosine and guanosine from the heart, without any noticeable effect on hypoxanthine and xanthine.
Conclusions: Coronary sinus concentrations of purines provide only a limited insight into the metabolism of the porcine heart. Repeated biopsies of the heart muscle and HPLC determinations of purine profiles represent a comprehensive and unique method for the study of purine metabolism during ischaemia and reperfusion. Future research on myocardial metabolism in disease and during cardiosurgical procedures should additionally be oriented to deficits in guanine and pyridine nucleotides.