Carrier-mediated transport of amino-cephalosporins by brush border membrane vesicles isolated from rat kidney cortex

The uptake of cephalosporin antibiotics by brush border membrane vesicles isolated from rat renal cortex has been studied by a rapid filtration technique, demonstrating a carrier-mediated transport system for amino-cephalosporins such as cephalexin and cephradine. The antibiotics were taken up into an osmotically reactive intravesicular space. The uptake of cephalexin was saturable (apparent Km2.2 mM), was inhibited by structural analogues and sulfhydryl reagents, and was stimulated by the countertransport effect, although the Na+ gradient did not affect the uptake. This transport system was essentially different from the transport system for p-aminohippurate in brush border membranes. The uptake properties for cephradine in brush border membrane vesicles appeared to be similar to those for cephalexin. The present results suggest the existence of a carrier-mediated transport system for amino-cephalosporins in brush border membranes. This system may be a part of the mechanism of tubular reabsorption of these antibiotics.