S. Kitagawa et Y. Sugaya, CHARACTERISTICS OF UPTAKE OF CEFROXADINE BY RABBIT SMALL-INTESTINAL BRUSH-BORDER MEMBRANE-VESICLES, Biological & pharmaceutical bulletin, 19(2), 1996, pp. 268-273
Characteristics of transport of an oral animocephalsoporin. cefroxadin
e. in rabbit small intestinal brush border membrane vesicles were exam
ined. Uptake rate of cefroxadine was saturable in the presence of an i
nward H+ gradient, and kinetic parameters were similar to those of cep
hradine. However, the uptake rate was almost linear with the concentra
tion in the absence of inward H+ gradient up to 5 mM. Overshoot phenom
enon was observed in the presence of an inward H+ gradient at 37 degre
es C, but it disappeared with decrease of temperature. The Arrhenius p
lot of uptake rate constant showed a break point at approximately 30 d
egrees C. Cefroxadine uptake was optimum in the vicinity of pH 5.5 at
37 degrees C, but the dependence on extravesicular pH disappeared at 1
5 degrees C. The uptake of cefroxadine but the inhibition was only sli
ght in the absence of an inward H+ gradient. Alkyl alcohols such as n-
hexyl alcohol also inhibited H+-coupled uptake of cefroxadine at the c
oncentration range at which the alcohols increased the membrane fluidi
ty, and overshoot phenomenon diminished, suggesting that H+-coupled tr
ansport of cefroxadine is sensitive to the alcohol-induced increase in
membrane fluidity. On the other hand, the alcohols rather stimulated
its uptake in the absence of an H+ gradient.