Bishop David, Edge Johann, Thomas Claire, Mercier Jacques
School of Human Movement and Exercise Science, The Univ. of Western Australia, Crawley, WA 6009, Australia.
J Appl Physiol (1985). 2007 Feb;102(2):616-21. doi: 10.1152/japplphysiol.00590.2006. Epub 2006 Nov 2.
The regulation of intracellular pH during intense muscle contractions occurs via a number of different transport systems [e.g., monocarboxylate transporters (MCTs)] and via intracellular buffering (beta m(in vitro)). The aim of this study was to investigate the effects of an acute bout of high-intensity exercise on both MCT relative abundance and beta m(in 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. Beta m(in 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 beta m(in vitro) (-11%; 135 +/- 3 to 120 +/- 2 micromol H+ x g dry muscle(-1) x 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 preparations and beta m(in vitro). Until the time course of these changes has been established, researchers should consider the possibility that observed training-induced changes in MCT and beta m(in 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.
在剧烈肌肉收缩过程中，细胞内pH值的调节通过多种不同的转运系统（如单羧酸转运体（MCTs））以及细胞内缓冲作用（体外βm）来实现。本研究的目的是调查一次急性高强度运动对人体MCT相对丰度和体外βm的影响。六名活跃女性自愿参与本研究。在静息状态下以及在以最大摄氧量的200%进行45秒运动后立即获取股外侧肌活检样本。通过滴定法测定体外βm，通过蛋白质免疫印迹法在膜制剂中测定MCT相对丰度。高强度运动与MCT1（-24%）和MCT4（-26%）的显著降低以及体外βm的降低（-11%；从135±3降至120±2微摩尔H⁺×克干肌肉⁻¹×pH⁻¹；P<0.05）相关。在所有受试者中均一致观察到这些变化，并且MCT1和MCT4相对丰度的变化之间存在显著相关性（R² = 0.92；P<0.05）。总之，单次高强度运动降低了膜制剂中的MCT相对丰度和体外βm。在确定这些变化的时间进程之前，如果在训练计划完成后不久进行活检，研究人员应考虑到观察到的训练诱导的MCT和体外βm变化可能受到最后一次运动 bout 的急性影响的可能性。这些发现对急性力竭运动后乳酸（和H⁺）转运的影响值得进一步研究。
