title: 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.
  
  
  METHODS
  6 Thoroughbreds (3 males and 3 females).
  
  
  METHODS
  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 quantified.
  
  
  RESULTS
  Compared with findings when horses were 2 months old, MCT1 protein content in GMM samples obtained when the horses were 24 months old was significantly higher; however, MCT4 protein content remained unchanged throughout the study period. Peroxisome proliferator-activated receptor-γ coactivator-1α content was significantly increased at 24 months of age and citrate synthase activity was increased at 6 and 24 months of age, compared with findings 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 significantly higher than those at 2 months of age.
  
  
  CONCLUSIONS
  Changes in protein contents of MCTs and the lactate dehydrogenase isoenzyme profile in GMM samples suggested that lactate usage capacity increases with growth and is accompanied by an increase in the oxidative capacity in Thoroughbreds.
authors.affiliation: Department of Exercise Physiology, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tennodai 1-1-1, Tsukuba, Ibaraki 305-8574, Japan.
authors.forename: Yu
authors.initials: Y
authors.lastname: Kitaoka
authors.forename: Daisuke
authors.initials: D
authors.lastname: Hoshino
authors.forename: Kazutaka
authors.initials: K
authors.lastname: Mukai
authors.forename: Atsushi
authors.initials: A
authors.lastname: Hiraga
authors.forename: Tohru
authors.initials: T
authors.lastname: Takemasa
authors.forename: Hideo
authors.initials: H
authors.lastname: Hatta
mesh_terms: D000818:Animals; D001693:Biological Transport, Active; D002950:Citrate (si)-Synthase / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D004734:Energy Metabolism; D005260:Female; D015870:Gene Expression; D006736:Horses / Q000254:growth & development / Q000378:metabolism*; D007527:Isoenzymes / Q000378:metabolism; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008137:Longitudinal Studies; D008297:Male; D027501:Monocarboxylic Acid Transporters / Q000235:genetics / Q000378:metabolism*; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000378:metabolism*; D025221:Phosphofructokinases / Q000378:metabolism; D027981:Symporters / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism; D000099233:Monocarboxylate Transport Protein 1
chemical_list: D002950:Citrate (si)-Synthase; D007527:Isoenzymes; D007770:L-Lactate Dehydrogenase; D027501:Monocarboxylic Acid Transporters; D009124:Muscle Proteins; D025221:Phosphofructokinases; D027981:Symporters; D014157:Transcription Factors; D000099233:Monocarboxylate Transport Protein 1