Effect of growth on monocarboxylate transporters and indicators of energy metabolism in the gluteus medius muscle of thoroughbreds

Abstract

Objective-To examine the changes in monocarboxylate transporter (MCT) 1 and MCT4 content and in indicators of energy metabolism in the gluteus medius muscle (GMM) of Thoroughbreds during growth.Animals-6 Thoroughbreds (3 males and 3 females).Procedures-Samples of GMM were obtained when horses were 2, 6, 12, and 24 months old. Muscle proteins were separated via SDS-PAGE; amounts of MCT1 and MCT4 and peroxisome proliferator-activated receptor-γ coactivator-1α content were determined by use of western blotting. Muscle activities of phosphofructokinase and citrate synthase were measured biochemically; lactate dehydrogenase isoenzymes were separated by agarose gel electrophoresis and quantifed.Results-Compared with fndings when horses were 2 months old, MCT1 protein content in GMM samples obtained when the horses were 24 months old was signifcantly higher; however, MCT4 protein content remained unchanged throughout the study period. Peroxi-some proliferator-activated receptor-γ coactivator-1α content was signifcantly increased at 24 months of age and citrate synthase activity was increased at 6 and 24 months of age, compared with fndings at 2 months. Phosphofructokinase activity remained unaltered during growth. The percentage contributions of lactate dehydrogenase 1 and 2 isoenzymes to the total amount of all 5 isoenzymes at 12 and 24 months of age were signifcantly higher than those at 2 months of age.Conclusions and Clinical Relevance-Changes in protein contents of MCTs and the lac-tate dehydrogenase isoenzyme profle in GMM samples suggested that lactate usage capacity increases with growth and is accompanied by an increase in the oxidative capacity in Thoroughbreds.