THE INTESTINAL TRANSPORT MECHANISM OF FLUOROQUINOLONES - INHIBITORY EFFECT OF CIPROFLOXACIN, AN ENOXACIN DERIVATIVE, ON THE MEMBRANE POTENTIAL-DEPENDENT UPTAKE OF ENOXACIN

Purpose. To clarify the absorption-structure relationship for the fluo roquinolones from the point of view of inhibitory behavior. Methods, T he inhibitory effects of ciprofloxacin on the transport process of eno xacin across the rat intestinal blush-border membrane was examined. Re sults, Ciprofloxacin, which has a similar structure to enoxacin, exhib ited a pH-dependent interference with enoxacin absorption from rat jej unal loops. The uptake experiments using BBM vesicles showed that cipr ofloxacin significantly reduced not only the initial binding of enoxac in to the membrane surface, hut also the K+- or H+-diffusion potential -dependent transport across the membrane. Furthermore, an H+-diffusion potential (interior negative) also exhibited a stimulative uptake of ciprofloxacin. Conclusions. These results suggest that the inhibition behavior of ciprofloxacin from the jejunal loop was closely related to the ionic diffusion potential-dependent uptake of enoxacin across the brush-border membrane.