Red cell metabolism affects lactate and pyruvate partition across the plasma membrane

The influence on red cell metabolism of increasing the glucose concentration or the pH of the medium has been examined in order to compare the modification of the lactate/pyruvate ratio inside and outside the cell. In both situations, we evidenced a constancy in the intracellular lactate/pyruvate ratio and an increase in the extracellular one, thus suggesting that the cell efficiently opposes cytoplasmic modifications. In fact an increase of lactate efflux takes place when the intracellular pyruvate decreases. The implications of these changes in the two compartments are discussed on the basis of the available results.