Despite the importance of short chain fatty acids (SCFA) in maintaining the ruminant physiology, the mechanism of SCFA absorption is still not fully studied. Therefore, this study was carried out to elucidate the mechanism of SCFA transport in the caprine rumen epithelia by investigating the possible involvement of monocarboxylate transporter 1 (MCT1) as well as to delineate the precise localization and the level of MCT1 protein along the caprine gastrointestinal tract. To achieve these objectives, molecular studies including: RT-PCR, Western blotting, and immunohistochemistry as well as functional studies (in vivo and in vitro) were used. RT-PCR studies revealed the presence of mRNA encoding for MCT1 in all regions of the caprine gastrointestinal tract. By immunoblotting analysis on membrane protein extract, a 45-kDa-band corresponding to MCT1 was detected in all parts of the forestomach and abomasum as well as along the entire length of the intestine. The MCT1 protein level was found most abundantly in forestomach, at intermediate levels in large intestine and abomasum, and lower levels in small intestine. MCT1 is immunolocalized mostly to the stratum basale and stratum spinosum of the caprine rumen epithelia. The MCT1 inhibitor, pCMB exerted a significant influence on acetate flux in vitro as well as short-chain fatty acids absorption in vivo. The results obtained provide evidence, for the first time, for transepithelial transport of SCFA via MCT1 across the caprine ruminal epithelia. [J Physiol Sci. 2006;56 Suppl:S77]
