The stimulative effect of diffusion potential on enoxacin uptake across rat intestinal brush-border membranes

J Pharm Pharmacol. 1994 Aug;46(8):676-9. doi: 10.1111/j.2042-7158.1994.tb03881.x.


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.

MeSH terms

  • Animals
  • Biological Transport, Active / drug effects
  • Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / pharmacology
  • Chlorides / metabolism
  • Chromatography, High Pressure Liquid
  • Dipeptides / pharmacology
  • Enoxacin / metabolism*
  • Enoxacin / pharmacokinetics
  • Glycine / metabolism
  • Glycine / pharmacology
  • Guanidine
  • Guanidines / pharmacology
  • Hydrogen-Ion Concentration
  • In Vitro Techniques
  • Ionophores / pharmacology
  • Male
  • Membrane Potentials / drug effects
  • Microvilli / drug effects
  • Microvilli / metabolism*
  • Patch-Clamp Techniques
  • Potassium / metabolism
  • Rats
  • Rats, Wistar
  • Valinomycin / pharmacology


  • Chlorides
  • Dipeptides
  • Guanidines
  • Ionophores
  • Valinomycin
  • Enoxacin
  • Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone
  • Guanidine
  • Potassium
  • Glycine