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  • Title: The stimulative effect of diffusion potential on enoxacin uptake across rat intestinal brush-border membranes.
    Author: Hirano T, Iseki K, Miyazaki S, Takada M, Kobayashi M, Sugawara M, Miyazaki K.
    Journal: J Pharm Pharmacol; 1994 Aug; 46(8):676-9. PubMed ID: 7815283.
    Abstract:
    Evidence of a membrane potential dependence for enoxacin uptake by rat intestinal brush-border membrane vesicles has been found. The transient overshooting uptake of enoxacin disappeared in the voltage-clamped brush-border membrane vesicles in the presence of an outward H(+)-gradient. Momentary dissipation of the H(+)-gradient itself by carbonyl cyanide p-(trifluoromethoxy)phenylhydrazone (FCCP) did not affect the uptake of enoxacin. In contrast, enoxacin uptake was depressed by an interior positive K(+)-diffusion potential induced by valinomycin. Furthermore, not only the outward H(+)-gradient but also an inward Cl(-)-gradient caused a stimulating effect on enoxacin uptake, and the stimulation by the Cl(-)-gradient was dissipated by using voltage-clamped membrane vesicles. These results indicate that enoxacin transportation across the brush-border membrane is dependent on the ionic diffusion potential. On the other hand, neither Gly-Gly nor guanidine had any effect on enoxacin uptake by the membrane vesicles in the presence of an inward (for Gly-Gly) or outward (for guanidine) H(+)-gradient as a driving force for each transport system. Therefore, it seems that enoxacin transport through the intestinal epithelia does not participate in the carrier-mediated transport systems for Gly-Gly and guanidine.
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