Effect of decreased O2 supply to tissue on the lactate: pyruvate ratio in blood.

Experiments were performed with trained conscious dogs with permanently implanted intravascular catheters. With the dogs in a basal resting state, the concentrations of lactate (L) and pyruvate (P) in arterial blood fluctuated widely from day to day, whereas their concentration ratio (L/P) remained relatively constant. By contrast, decrease in tissue O(2) supply induced by severe chronic anemia increased the arterial blood L/P, specifically, with only random accompanying changes in the lactate or pyruvate concentrations themselves. When systemic O(2) consumption was increased acutely by muscular exercise, cardiac output increased, and the changes in blood L/P were small and not consistent between different dogs. But when O(2) supply to the tissues was simultaneously limited by anemia, L/P increased during exercise, and the magnitude of the increase was proportional to the severity of the anemia. These results suggest that changes in blood L/P during exercise are related specifically to tissue O(2) supply.