Takano Mikihisa, Koyama Yuka, Nishikawa Hiromi, Murakami Teruo, Yumoto Ryoko
Department of Pharmaceutics and Therapeutics, Programs for Pharmaceutical Sciences, Graduate School of Biomedical Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8551, Japan.
Eur J Pharmacol. 2004 Oct 11;502(1-2):149-55. doi: 10.1016/j.ejphar.2004.08.041.
Absorption of fluorescein isothiocyanate-labeled lysozyme (FITC-lysozyme) was examined in rat small intestine. Messenger RNA of megalin, an endocytic receptor for lysozyme in the kidney, was expressed in the lower but not in the upper intestine. In in situ closed loop and recirculation methods, absorption of FITC-lysozyme from the upper intestine was much higher than from the lower intestine. The absorption rate of FITC-lysozyme in the upper intestine was significantly higher than FITC-dextran and was inhibited by unlabeled lysozyme in a concentration-dependent manner. The absorption of FITC-lysozyme was also inhibited by spermine and phenylarsine oxide. These results indicate that the intestinal absorption of lysozyme is segment-selective and occurs preferentially from the upper intestine. Megalin expressed in the lower intestine appears not to have a significant role in the absorption of lysozyme. In the upper intestine, lysozyme appears to be absorbed by an endocytic pathway, and cationic charge may be important for lysozyme absorption.
在大鼠小肠中检测了异硫氰酸荧光素标记的溶菌酶（FITC-溶菌酶）的吸收情况。巨膜蛋白是肾脏中溶菌酶的一种内吞受体，其信使核糖核酸在小肠下段表达，而在上段不表达。采用原位闭环和再循环方法，FITC-溶菌酶从小肠上段的吸收远高于下段。FITC-溶菌酶在上段小肠的吸收速率显著高于FITC-葡聚糖，且被未标记的溶菌酶以浓度依赖的方式抑制。精胺和苯砷酸氧化物也抑制FITC-溶菌酶的吸收。这些结果表明，溶菌酶的肠道吸收具有节段选择性，且优先从小肠上段发生。在小肠下段表达的巨膜蛋白似乎在溶菌酶的吸收中没有显著作用。在小肠上段，溶菌酶似乎通过内吞途径被吸收，阳离子电荷可能对溶菌酶的吸收很重要。
