MESSENGER-RNAS OF ENZYMES INVOLVED IN ENERGY-METABOLISM AND MTDNA AREINCREASED IN ENDURANCE-TRAINED ATHLETES

Improvements in endurance capacity by training are associated with str uctural and biochemical adaptations of working muscles that affect the mitochondrial compartment. We investigated whether the 1.8-fold highe r mitochondrial volume density in a group of endurance-trained athlete s compared with untrained subjects was reflected by higher steady-stat e levels of mRNAs coding for components of the oxidative phosphorylati on pathway using a quantitative polymerase chain reaction approach. We found that mitochondrially encoded RNAs (cytochrome-c oxidase subunit I, NADH reductase subunit 6, 168 rRNA), as well. as nuclear-encoded R NAs (cytochrome-c oxidase subunit IV, succinate dehydrogenase, fumaras e) are all increased coordinately in the athletes (1.54- to 1.94-fold) . In addition, mitochondrial (mt) DNA concentration was also 1.55-fold higher in the trained athletes, whereas genomic DNA was not changed. Our findings thus show similar RNA expression of mitochondrially encod ed genes in sedentary and endurance-trained subjects, whereas pretrans lational control mechanisms account for higher levels of nuclear-encod ed RNAs in the athletes.