Yamamoto A, Sakane T, Shibukawa M, Hashida M, Sezaki H
Department of Basic Pharmaceutics, Faculty of Pharmaceutical Sciences, Kyoto University, Japan.
J Pharm Sci. 1991 Nov;80(11):1067-71. doi: 10.1002/jps.2600801114.
Absorption and metabolic characteristics of p-aminobenzoic acid (PABA) and m-aminobenzoic acid (MABA) from the rat small intestine were examined by means of in situ recirculation and in vitro everted sac experiments. p-Aminobenzoic acid was extremely rapidly absorbed from the rat small intestine, whereas the absorption of MABA, the m-isomer of PABA, was comparably slower. This finding was partly explained by the result that PABA is more lipophilic than MABA. The metabolite percentage of PABA was considerably greater than that of MABA in mucosal fluid, tissue, and serosal fluid. On the other hand, a concentration-dependent and a directional difference in the transfer rate of these drugs were observed in everted and noneverted sacs of rat small intestine. Furthermore, mucosal uptake of PABA or MABA was inhibited by 1 mM 2,4-dinitrophenol, 10 mM sodium azide, and pretreatment with HgCl2 (10 mM). These results indicate that MABA, as well as PABA, is transported through the intestine by a carrier-mediated transport system, and that the molecular structure of these drugs is important for their absorption and metabolic characteristics.
通过原位再循环和体外外翻肠囊实验研究了对氨基苯甲酸（PABA）和间氨基苯甲酸（MABA）在大鼠小肠中的吸收和代谢特性。对氨基苯甲酸从大鼠小肠吸收极快，而PABA的间位异构体MABA的吸收相对较慢。这一发现部分可由PABA比MABA更具亲脂性这一结果来解释。在黏膜液、组织和浆膜液中，PABA的代谢物百分比远高于MABA。另一方面，在大鼠小肠的外翻和未外翻肠囊中观察到这些药物转运速率存在浓度依赖性和方向性差异。此外，1 mM 2,4-二硝基苯酚、10 mM叠氮化钠以及用HgCl2（10 mM）预处理可抑制PABA或MABA的黏膜摄取。这些结果表明，MABA与PABA一样，是通过载体介导的转运系统在肠道中转运的，并且这些药物的分子结构对其吸收和代谢特性很重要。
