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This Article Full Text Full Text (PDF) All Versions of this Article: 91/5/835    most recent expphysiol.2006.033837v1 Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Kirat, D. Articles by Kato, S. Search for Related Content PubMed PubMed Citation Articles by Kirat, D. Articles by Kato, S. Related Collections GI & Epithelial

¹ Department of Veterinary Physiology, School of Veterinary Medicine, Rakuno Gakuen University, 582 Bunkyodai-Midorimachi, Ebetsu, Hokkaido 069-8501, Japan

The present study was undertaken to investigate the functional role of monocarboxylate transporter 1 (MCT1) in the ruminant large intestine. Messenger RNA encoding for MCT1 was verified by reverse transcriptase-polymerase chain reaction in caecum, proximal colon and distal colon of adult cattle. Both immunohistochemistry and confocal laser microscopy verified that the MCT1 protein was abundant in the surface epithelium of the large intestine, and the amount decreased from the opening of the crypt to its base. In the immunopositive cells, MCT1 was primarily localized in the basolateral membranes of epithelium lining the large intestine. Western blotting indicated that the levels of MCT1 protein were highest in the caecum, followed by proximal colon and then distal colon. In vitro studies were conducted to elucidate the possible involvement of MCT1 in the transport of short-chain fatty acids (SCFA) across the isolated mucosal sheets of cattle caecum using the Ussing chamber technique. Acetate absorption was found to be pH dependent, and the rate of acetate absorption increased as pH decreased. The serosal application of the MCT1 inhibitor ‘p-chloromercuribenzoic acid (pCMB)’ significantly reduced the transport of acetate across the caecal epithelium of cows. In addition, the transport of acetate was significantly reduced in the presence of its analogue, propionate, indicating that acetate and propionate compete for binding to the same transporter. The results show that MCT1 is a major route for SCFA efflux across the basolateral membrane of bovine large intestine and that it could play a role in the regulation of intracellular pH.

(Received 2 March 2006; accepted after revision 10 July 2006; first published online 20 July 2006)
Corresponding author S. Kato: Department of Veterinary Physiology, School of Veterinary Medicine, Rakuno Gakuen University, 582 Bunkyodai-Midorimachi, Ebetsu, Hokkaido 069-8501, Japan. Email: kato{at}rakuno.ac.jp