Monocarboxylate transporters (MCT) as lactate carriers in equine muscle and red blood cells

Abstract

Monocarboxylate transporters (MCT) facilitate the transport of lactate across membranes. In red blood cells (RBC) the transport activity varies interindividually due to differences in the amount of an ancillary protein CD147. Similar variations in muscles could have a great influence on lactate accumulation during exercise. To study the expression of MCT isoforms and CD147 in the middle gluteal muscle. Venous blood and muscle biopsy samples were taken from 14 Standardbred horses. Lactate transport activity in RBC and the amounts of MCT1, 2, 4 and CD147 were measured. In muscle MCT1, MCT4 and CD147 were found. Amount of MCT1 was variable and not dependent on age or training. Expression of MCT4 increased with age and correlated positively with CD147. CD147 in muscle correlated with that in RBC. MCT4 in muscle and CD147/MCT1 in RBC were higher in race fit than in moderately trained horses. MCT isoform profile in equine muscle is similar to that in man. The correlation between CD147 in muscle and RBC supports the view that lactate transport activity in muscles may vary interindividually as with RBC. A larger number of horses need to be analysed to confirm the relationship of CD147 in muscle and RBC; and to allow the use the lactate transport activity in RBC as an indicator of the respective activity in muscles.