Iwanaga Toshihiko, Takebe Kumiko, Kato Ikuo, Karaki Shin-Ichiro, Kuwahara Atsukazu
Laboratory of Histology and Cytology, Graduate School of Medicine, Hokkaido University, Sapporo, Japan.
Biomed Res. 2006 Oct;27(5):243-54. doi: 10.2220/biomedres.27.243.
Short-chain fatty acids (SCFA) are monocarboxylates produced by bacterial fermentation that play a crucial role in maintaining homeostasis in the large intestine. Two major transporters for SCFA, monocarboxylate transporter (MCT) and slc5a8 (or SMCT), exist in the digestive tract. The present histochemical study using in situ hybridization and immunohistochemistry revealed the distribution and subcellular localization of the MCT family in the digestive tract of mice, rats, and humans, comparing these with that of slc5a8. The expression of mucosal MCT1 in the mouse and rat was most intense in the cecum, followed by the colon, but low in the stomach and small intestine. Among other MCT subtypes, only MCT2 was detected in the parietal cell region of the gastric mucosa. Slc5a8 had predominant expression sites in the distal half of the large bowel and in the most terminal ileum. The mucosal MCT1 was localized in the basolateral membrane of enterocytes, while slc5a8 was restricted to the apical cell membrane, suggesting the involvement of slc5a8 in the uptake of luminal SCFA, and of MCT1 in the efflux of SCFA and monocarboxylate metabolites towards blood circulation. The large intestine expressed both types of the transporter, but their distribution patterns differed along the longitudinal axis of the intestine and along the perpendicular axis of the mucosa.
短链脂肪酸（SCFA）是细菌发酵产生的单羧酸盐，在维持大肠内环境稳定中起关键作用。消化道中存在两种主要的SCFA转运体，即单羧酸盐转运体（MCT）和slc5a8（或SMCT）。本研究采用原位杂交和免疫组织化学方法，揭示了MCT家族在小鼠、大鼠和人类消化道中的分布及亚细胞定位，并与slc5a8进行了比较。小鼠和大鼠黏膜MCT1在盲肠中表达最强，其次是结肠，而在胃和小肠中表达较低。在其他MCT亚型中，仅在胃黏膜壁细胞区域检测到MCT2。Slc5a8在大肠远端和最末端回肠有主要表达位点。黏膜MCT1定位于肠上皮细胞的基底外侧膜，而slc5a8局限于顶端细胞膜，这表明slc5a8参与腔内SCFA的摄取，而MCT1参与SCFA和单羧酸盐代谢产物向血液循环的外排。大肠表达这两种转运体，但它们的分布模式在肠道纵轴和黏膜垂直轴上有所不同。
