Factors influencing the metabolic pathways of glucose in human erythrocytes

The metabolic effect of a lactate or pyruvate load and methylene blue (Mb) on hexose monophosphate shunt (HMPS) and Embden-Meyerhof pathway (EMP) were investigated in intact erythrocytes in the presence of glucose. Pyruvate enhances glucose consumption and 14CO2 production, lactate reduces 14CO2 production but glucose consumption is unchanged. These effects are dependent on the lactate and pyruvate concentrations in the buffer. A pyruvate load does not results to influence the net production of pyruvate, which is conversely markedly increased by Mb. The lactate load raises slightly the total pyruvate level but its rate of production is unchanged, with respect to that of the control. A considerable effect on the intracellular to extracellular pyruvate ratio is observed in these different conditions, as well as modifications in the levels of inorganic phosphate (Pi).