Transport mechanism of ceftibuten, a dianionic cephem, in rat renal brush-border membrane.

The uptake mechanism of ceftibuten by rat renal brush-border membrane vesicles was investigated. Uptake was found to be independent of a Na+ gradient and partially dependent on an inwardly directed H(+)-gradient. Competition experiments between ceftibuten and several compounds demonstrated that the peptide-like structural features of inhibitors are more essential than their charge properties for inhibiting uptake. Anionic compound, such as p-aminohippuric acid, also inhibited ceftibuten uptake by renal brush-border membrane vesicles in the presence of an H(+)-gradient. We conclude that ceftibuten, in spite of its anionic structure, is transported via the dipeptide transport systems, rather than the organic anion transport system.