pH-dependent inhibitory effects of angiotensin-converting enzyme inhibitors on cefroxadine uptake by rabbit small intestinal brush-border membrane vesicles and their relationship with hydrophobicity and the ratio of zwitterionic species.

The inhibitory effects of five angiotensin-converting enzyme (ACE) inhibitors on the uptake of an aminocephalosporin antibiotic, cefroxadine, by rabbit small intestinal brush-border membrane vesicles were examined in the presence of an inward H+ gradient. Dixon plot analysis showed that all these ACE inhibitors inhibited the uptake of cefroxadine, which is transported by a H+/oligopeptide transporter in the membrane, in the order of enalapril