The mechanism of lactate transport in human erythrocytes

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Abstract
Lactate accumulates in human erythrocytes stored at 4°C in the presence of glucose. Efflux of lactate exhibits an activation energy of 22 kcal/mole and is markedly stimulated with increasing medium pH. Lactate influx into erythrocytes that were depleted of intracellular lactate by incubation at 37° at pH 8.0 was stimulated by decreasing medium pH. Under appropriate conditions the pH-dependent lactate flux was insensitive to 4-acetamido-4′-isothiocyano-2,2′-disulfonic stilbene or 4,4′-diisothiocyano-2,2′-disulfonic stilbene, inhibitors of the inorganic anion channel, while, e.g., inorganic phosphate transport was fully sensitive. These experiments as well as measurements of H+ movements associated with lactate fluxes demonstrate that lactate transport takes place via a specific monocarboxylate transporter (distinct from the inorganic ion channel) by a H+-lactate symport mechanism.