The aim of the present study was to determine possible direct adverse effects of a 2-hour Escherichia coli endotoxin infusion (50 ng kg-1 min-1) on myocardial oxidative carbohydrate metabolism. The experiments were performed in intact dogs to assay glucose and lactate cardiac uptake and relate them to oxygen consumption (MVO2), CO2 production, and myocardial hemodynamics. Coronary sinus blood flow (CSBF) was measured by thermodilution, and the arteriovenous differences in glucose, lactate, pyruvate, O2, and CO2 were determined by blood samples obtained simultaneously from the carotid artery and sinus coronary. The adequacy of CSBF in meeting cardiac oxygen needs was evaluated by calculating the percentage of anaerobic metabolic rate (% AMR). During endotoxin infusion, CSBF was significantly lowered by 33% while mean aortic blood pressure was decreased by 43%. Cardiac index exhibited a minimal reduction of 14%. Mean arterial blood glucose decreased 30% and arterial lactate increased 100%. Despite the progressively developing hypoglycemia, cardiac glucose uptake increased 140%. Although MVO2 was reduced to 70% of control value, lactate uptake increased 50%. Throughout the experimental period, the % AMR remained negative. Under endotoxin infusion, up to 78% of the cardiac CO2 production was derived from carbohydrate utilization, as compared to 40% prior to endotoxin infusion. Our findings suggest the absence of any toxic action by an endotoxin-sustained infusion on cardiac oxidative metabolism.