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Abstract

The uptake of L-lactate by rat small intestinal brush-border and basal-lateral plasma membrane vesicles has been studied. L-Lactate uptake by the isolated membrane vesicles is osmotically sensitive and represents predominantly transport into an intravesicular space and not binding to the membranes.

The transport of L-lactate across the brush-border membrane is stimulated by sodium, whereas the transport across the basal-lateral plasma membrane is sodium-independent. In both types of membrane vesicles L-lactate is transported faster than D-lactate and L-lactate transport is inhibited by α-cyano-cinnamic acid. L-Lactate transport across basal-lateral membranes is inhibited by D-lactate and pyruvate and transstimulated by L-lactate and pyruvate.

The polar distribution of transport system for Lactate in the plasma membrane of rat enterocytes—a Na⁺/L-lactate cotransport system in the brush-border membrane and a facilitated diffusion system in the basal-lateral membrane — can explain the fact that in the intact epithelium L-lactate produced by cell metabolism is preferentially released on the serosal side and could enable the cell to perform vectorial, secondary active transport of L-lactate from the intestinal lumen to the serosal compartment