Carrier-mediated uptake of cephalexin in human intestinal cells.

A transport carrier for cephalexin, a cephalosporin antibiotic, was identified in a human intestinal cell line, HT-29. Uptake via the carrier was inhibited by dipeptides, phe-gly, gly-pro, carnosine, and cefaclor, a close drug analog. Uptake was unaffected by the presence of amino acids. The pH optimum for uptake was 6.2. Drug uptake was not dependent on the presence of sodium and was insensitive to metabolic inhibitors. The efflux of cephalexin was stimulated by extracellular carnosine, indicating counter-transport. Taken together, drug uptake is mediated by a dipeptide transport carrier and not by an amino acid transport carrier. This is the first demonstration of the carrier in an established cell line.