Polar distribution of sodium-dependent and sodium-independent transport system for L-lactate in the plasma membrane of rat enterocytes.
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 alpha-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 L-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.
D000818:Animals; D001693:Biological Transport, Active; D002462:Cell Membrane / Q000378:metabolism; D066298:In Vitro Techniques; D007413:Intestinal Mucosa / Q000378:metabolism*; D007422:Intestines / Q000166:cytology; D007773:Lactates / Q000378:metabolism*; D009994:Osmolar Concentration; D011773:Pyruvates / Q000378:metabolism; D051381:Rats; D012964:Sodium / Q000502:physiology*
D007773:Lactates; D011773:Pyruvates; D012964:Sodium