Kirat Doaa, Kondo Koji, Shimada Ritsu, Kato Seiyu
Department of Veterinary Physiology, School of Veterinary Medicine, Rakuno Gakuen University, 582-1 Bunkyodai-Midorimachi, Ebetsu, Hokkaido 069-8501, Japan.
Exp Physiol. 2009 Apr;94(4):422-33. doi: 10.1113/expphysiol.2009.046797. Epub 2009 Jan 23.
This work was undertaken to study the effect of pectin feeding on the expression level, cellular localization and functional activity of monocarboxylate transporter 1 (MCT1) in the gastrointestinal tract of rats. The results indicated that MCT1 protein level was significantly increased along the entire length of the gastrointestinal tract of pectin-fed rats in comparison with control animals. Immunohistochemical analysis revealed an increase in MCT1 in the stratified squamous epithelia of the forestomach as well as in the basolateral membranes of the cells lining the gastric pit of the glandular stomach of pectin-fed rats when compared with control animals. The parietal cells, which showed barely any or no detectable MCT1 in the control group, exhibited a strong intensity of MCT1 on the basolateral membranes in pectin-fed rats. In the small intestine of pectin-fed rats, strong immunopositivity for MCT1 was detected in the brush border and basolateral membranes of the absorptive enterocytes lining the entire villi, while in control rats, weak reactivity was detected on the brush border membrane in a few absorptive enterocytes in the villus tip. In the large intestine of control animals, MCT1 was detected on the basolateral membranes of the epithelia lining the caecum and colon. This staining intensity was markedly increased in pectin-fed rats, along with the appearance of strong reactivity for MCT1 on the apical membranes of the surface and crypt epithelia of caecum and colon. Our results also showed that MCT1 co-localizes with its chaperone, basigin (CD147), in the rat gastrointestinal tract, and that the pectin feeding increased the expression of CD147. In vivo functional studies revealed an enhanced acetate absorption in the colon of pectin-fed in comparison with control animals. We conclude that MCT1 is up-regulated along the gastrointestinal tract of pectin-fed rats, which might represent an adaptive response to the increased availability of its substrates.
本研究旨在探讨喂食果胶对大鼠胃肠道中一元羧酸转运体1（MCT1）的表达水平、细胞定位及功能活性的影响。结果表明，与对照动物相比，喂食果胶的大鼠胃肠道全长中MCT1蛋白水平显著升高。免疫组织化学分析显示，与对照动物相比，喂食果胶的大鼠前胃复层鳞状上皮以及腺胃胃小凹内衬细胞的基底外侧膜中MCT1增加。对照组中几乎检测不到或未检测到MCT1的壁细胞，在喂食果胶的大鼠中其基底外侧膜上呈现出强MCT1强度。在喂食果胶的大鼠小肠中，在整个绒毛内衬的吸收性肠上皮细胞的刷状缘和基底外侧膜中检测到对MCT1的强免疫阳性，而在对照大鼠中，仅在绒毛顶端的少数吸收性肠上皮细胞的刷状缘膜上检测到弱反应性。在对照动物的大肠中，在盲肠和结肠内衬上皮的基底外侧膜上检测到MCT1。在喂食果胶的大鼠中，这种染色强度显著增加，同时盲肠和结肠表面及隐窝上皮的顶端膜上出现对MCT1的强反应性。我们的结果还表明，MCT1与其伴侣蛋白基底结合素（CD147）在大鼠胃肠道中共定位，并且喂食果胶增加了CD147的表达。体内功能研究表明，与对照动物相比，喂食果胶的大鼠结肠中乙酸盐吸收增强。我们得出结论，喂食果胶的大鼠胃肠道中MCT1上调，这可能代表对其底物可用性增加的一种适应性反应。
