Intracellular acidification and volume increases explain R2 decreases in exercising muscle
Open Access
- 20 December 2001
- journal article
- research article
- Published by Wiley in Magnetic Resonance in Medicine
- Vol. 47 (1) , 14-23
- https://doi.org/10.1002/mrm.10043
Abstract
Exercise‐induced decreases in the 1H transverse relaxation rate (R2) of muscle have been well documented, but the mechanism remains unclear. In this study, the hypothesis was tested that R2 decreases could be explained by pH decreases and apparent intracellular volume (Vi′) increases. 31P and 1H spectroscopy, biexponential R2 analysis, and imaging were performed prior to and following fatiguing exercise in iodoacetate‐treated (IAA, to inhibit glycolysis), NaCN‐treated (to inhibit oxidative phosphorylation), and untreated frog gastrocnemii. In all exercised muscles, the apparent intracellular R2 (R2i′) and pH decreased, while intracellular osmolytes and Vi′ increased. These effects were larger in NaCN‐treated and untreated muscles than in IAA‐treated muscles. Multiple regression analysis showed that pH and Vi′ changes explain 70% of the R2i′ variance. Separate experiments in unexercised muscles demonstrated causal relationships between pH and R2i′ and between Vi′ and R2i′. These data indicate that the R2 change of exercise is primarily an intracellular phenomenon caused by the accumulation of the end‐products of anaerobic metabolism. In the NaCN‐treated and untreated muscles, the R2i′ change increased as field strength increased, suggesting a role for pH‐modulated chemical exchange. Magn Reson Med 47:14–23, 2002.Keywords
This publication has 37 references indexed in Scilit:
- The Role of Specific Side Groups and pH in Magnetization Transfer in PolymersJournal of Magnetic Resonance, 1998
- The origin of biexponential T2 relaxation in muscle waterMagnetic Resonance in Medicine, 1993
- Effect of perfusion on exercised muscle: MR imaging evaluationJournal of Magnetic Resonance Imaging, 1992
- Muscle Activity Localization with31P Spectroscopy and Calculated T2-Weighted 1H ImagesInvestigative Radiology, 1991
- Direct Relationship Between Proton T2 and Exercise Intensity in Skeletal Muscle MR ImagesInvestigative Radiology, 1990
- Relative contributions of chemical exchange and other relaxation mechanisms in protein solutions and tissuesMagnetic Resonance in Medicine, 1989
- Nuclear magnetic resonance relaxation in experimental brain edema: Effects of water concentration, protein concentration, and temperatureMagnetic Resonance in Medicine, 1988
- Spin-echo water suppression for the generation of pure-phase two-dimensional NMR spectraJournal of Magnetic Resonance (1969), 1987
- Muscular fatigue investigated by phosphorus nuclear magnetic resonanceNature, 1978