BACKGROUND OG-VI is a solution composed of 30 mmol/l inosine, 30 mmol/l sodium 5'-guanylate, 30 mmol/l cytidine, 22.5 mmol/l uridine, and 7.5 mmol/l thymidine, which is known to improve myocardial stunning. OBJECTIVE To study the effect of OG-VI on myocardial energy and carbohydrate metabolism during ischemia. METHODS Ischemia was induced in pentobarbital-anesthetized open-chested dogs for 3 min by left anterior descending coronary artery ligation. Saline, 1.2 mmol/kg per min OG-VI, or 12 mmol/kg per min OG-VI was infused at 0.1 ml/kg per min, starting 30 min before the onset of ischemia. The myocardium was extracted 3 min after the onset of ischemia, and used to determine the tissue levels of energy and carbohydrate metabolites. RESULTS Ischemia decreased the levels of ATP and fructose 1,6 diphosphate significantly, and increased those of AMP, glucose 6 phosphate, fructose 6 phosphate and lactate. OG-VI infusion preserved the adenine nucleotide levels significantly in 3 min ischemic hearts, and attenuated the ischemia-induced alteration of carbohydrate metabolism. CONCLUSIONS OG-VI may improve the myocardial metabolic derangement induced by ischemia.