The pH Dependent Uptake of Enoxacin by Rat Intestinal Brush‐border Membrane Vesicles
The pH Dependent Uptake of Enoxacin by Rat Intestinal Brush‐border Membrane Vesicles
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大鼠肠刷状缘膜囊泡对依诺沙星的 pH 依赖性摄取
DOI：
10.1111/j.2042-7158.1992.tb05507.x
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发表时间：
1992
影响因子：
3.3
通讯作者：
K. Miyazaki
中科院分区：
文献类型：
--
作者：
K. Iseki;T. Hirano;Y. Fukushi;Yukie Kitamura;S. Miyazaki;M. Takada;M. Sugawara;H. Saitoh;K. Miyazaki
摘要-依诺沙星（一种口服活性氟喹诺酮类抗生素）的肠道转运机制已使用从大鼠小肠分离的刷状缘膜囊泡进行了研究。依诺沙星摄取的初始速率和时间过程在很大程度上取决于介质pH值（pH 5·5 > pH 7·5）和羧基的电离百分比（pKa 6·2，阴离子电荷），即阳离子形式的摄取程度高于两性离子形式。如囊外介质渗透压对稳态（30 min）依诺沙星摄取的影响所示，存在转运至囊内空间的证据。缬氨霉素诱导的K+-扩散电位（内部负）和向外的H+-扩散电位刺激了这种跨刷状缘膜的转运。此外，将培养基的pH从5.5改变为7.5显著降低了缬氨霉素诱导的K+扩散电位对依诺沙星摄取的影响。这些结果表明，依诺沙星的阳离子形式的摄取行为在依诺沙星的肠吸收过程中起着重要的作用。
Abstract— The mechanism of the intestinal transport of enoxacin, an orally active fluoroquinolone antibiotic, has been investigated using brush‐border membrane vesicles isolated from rat small intestine. The initial rate and time‐course of enoxacin uptake were considerably dependent upon the medium pH (pH 5·5 > pH 7·5) and upon the percent ionization of the carboxyl group (pKa 6·2, anionic charge), namely, the degree of uptake of cationic form was higher than that of the zwitterionic form. There was evidence of transport into the intravesicular space as shown by the effect of extravesicular medium osmolarity on enoxacin uptake at steady state (30 min). This transport across the brush‐border membrane was stimulated by the valinomycin‐induced K+‐diffusion potential (interior negative) and an outward H+‐diffusion potential. Furthermore, changing the pH of the medium from 5·5 to 7·5 significantly decreased the effect of valinomycin‐induced K+‐diffusion potential on the enoxacin uptake. These results suggest that the uptake behaviour of the cationic form of enoxacin plays an important role in the intestinal absorption process of enoxacin.
DOI：
10.1152/ajpgi.1988.255.1.g85
发表时间：
1988
期刊：
The American journal of physiology
影响因子：
--
作者：
Miyamoto,Y;Ganapathy,V;Leibach,FH
通讯作者：
Leibach,FH