Abstract
The aim of this study was to investigate the effects of an acute bout of high-intensity exercise on both MCT relative abundance and 13min vitro in humans. Six active women volunteered for this study. Biopsies of the vastus lateralis were obtained at rest and immediately after 45 s of exercise at 200% of maximum O2 uptake. 13min vitro was determined by titration, and MCT relative abundance was determined in membrane preparations by Western blots. High-intensity exercise was associated with a significant decrease in both MCT1 (-24%) and MCT4 (-26%) and a decrease in 13min vitro (-11%; 135 ± 3 to 120 ± 2µmol H+•g dry muscle-1•pH-1; P < 0.05). These changes were consistently observed in all subjects, and there was a significant correlation between changes in MCT1 and MCT4 relative abundance (R2 = 0.92; P < 0.05). In conclusion, a single bout of high-intensity exercise decreased both MCT relative abundance in membrane prep- arations and 13min vitro. Until the time course of these changes has been established, researchers should consider the possibility that observed training-induced changes in MCT and 13min vitro may be influenced by the acute effects of the last exercise bout, if the biopsy is taken soon after the completion of the training program. The implications that these findings have for lactate (and H+) transport following acute, exhaustive exercise warrant further investigation.