Cellular distribution of glutamate transporters in the gastrointestinal tract of mice: an immunohistochemical and in situ hybridization approach.
L-Glutamate transport by intestinal epithelial cells is an initial step of the entire glutamate metabolism pathway in the gut mucosa. The present study examined the cellular distribution of glutamate transporters in the digestive tract of adult mice using immunohistochemistry and in situ hybridization technique. Expression of EAAC1 mRNA was more intense in the ileum, where the epithelium in crypts and the basal half of intestinal villi showed high levels of transcripts, suggesting an essential role of EAAC1 in differentiating or premature epithelial cells. Electron-microscopically, EAAC1 immunoreactivity was predominantly localized in the striated border of enterocytes. Immunoreactivity for GLT-1 was found in the lateral membrane of epithelial cells at the bottom of gastric glands and at the intestinal crypts, and also in the lateral membrane of secretory cells at the duodenal gland. GLAST immunoreactivity was restricted to the fundic and pyloric glands, and was especially intense in the neck portion of both glands. However, in situ hybridization analysis failed to confirm the expression of GLT-1 and GLAST at the mRNA level, possibly due to limited sensitivity. The strong and specific luminal localization of EAAC1 in the intestinal epithelium suggests that EAAC1 is a predominant transporter of glutamate, at least in the lower part of the small intestine.
Iwanaga
Toshihiko
T
Department of Anatomy, Hokkaido University Graduate School of Medicine, Kita-ku, Sapporo 060-8638, Japan. tiwanaga@med.hokudai.ac.jp
Goto
Marie
M
Watanabe
Masahiko
M
D000818:Animals; D001692:Biological Transport / Q000502:physiology; D004386:Duodenum / Q000378:metabolism* / Q000648:ultrastructure; D020895:Enterocytes / Q000378:metabolism* / Q000648:ultrastructure; D005753:Gastric Mucosa / Q000378:metabolism* / Q000648:ultrastructure; D050491:Glutamate Plasma Membrane Transport Proteins / Q000096:biosynthesis*; D007082:Ileum / Q000378:metabolism* / Q000648:ultrastructure; D007150:Immunohistochemistry / Q000379:methods; D017403:In Situ Hybridization / Q000379:methods; D008297:Male; D051379:Mice; D009928:Organ Specificity / Q000502:physiology
D050491:Glutamate Plasma Membrane Transport Proteins