Expression of MCT1, MCT2 and MCT4 in the rumen, small intestine and liver of reindeer (Rangifer tarandus tarandus L.)

The expression of monocarboxylate transporters MCT1, MCT2 and MCT4 in the rumen, small intestine and liver was examined in free-ranging and captive reindeer. In addition, expression of chaperone protein CD147, which is needed for the activity of MCT1 and MCT4, was studied in the rumen of suckling calves. Immunoblotting of cell membrane proteins showed the expression of MCT1 and MCT4, but not that of MCT2 in the rumen of reindeer. In free-ranging reindeer the amount of MCT1 was higher than in the captive ones (P<0.01). Developing rumen of suckling calves expressed MCT1 and MCT4 and positive correlation was found between MCT1 and CD147. Both MCT1 and CD147 correlated also with age in calves less than 10 days. In the small intestine all the isoforms studied were expressed, but the amounts were lower than in the rumen (P<0.05). In the liver MCT1 and MCT2 were found while MCT4 was nearly undetectable. The expression of MCT isoforms in the rumen and small intestine reflects the site of absorption and concentrations of short chain fatty acids (SCFA). In the liver the expression of high affinity transporters, MCT1 and MCT2, is in accordance with almost complete uptake of propionate from portal blood.