RESUMEN
INTRODUCTION: The purpose of this study was to test the hypothesis that malignant hyperthermia model mice (RyR1Y522S/wt) are more vulnerable to exercise-induced muscle injury and fatigability and adapt less to run training. METHODS: After 6 weeks of voluntary wheel running, we measured anterior crural muscle fatigability, muscle injury, and cytochrome oxidase (COX) and citrate synthase (CS). RESULTS: Although RyR1Y522S/wt mice ran without undergoing MH episodes, they ran 42% less distance than wild-type (WT) mice. Muscles from WT mice exhibited increased fatigue resistance and COX content after training. Muscles from RyR1Y522S/wt mice demonstrated no significant change in fatigability or COX and CS after training. However, muscles from RyR1Y522S/wt mice displayed less intrinsic fatigability and greater COX/CS content and muscle damage than WT mice. CONCLUSIONS: RyR1Y522S/wt mice can run without having rhabdomyolysis, and their inability to adapt to training appears to stem from intrinsic enhancement of mitochondrial enzymes and fatigue resistance.
Asunto(s)
Hipertensión Maligna/metabolismo , Hipertensión Maligna/fisiopatología , Fatiga Muscular/fisiología , Músculo Esquelético/patología , Músculo Esquelético/fisiopatología , Condicionamiento Físico Animal/fisiología , Aerobiosis , Animales , Western Blotting , Citrato (si)-Sintasa/metabolismo , Susceptibilidad a Enfermedades , Complejo IV de Transporte de Electrones/metabolismo , Femenino , Contracción Isométrica/fisiología , Masculino , Ratones , Ratones Endogámicos C57BL , Mitocondrias Musculares/metabolismo , Fibras Musculares Esqueléticas/patología , Fuerza Muscular/fisiología , Cadenas Pesadas de Miosina/metabolismo , Tamaño de los Órganos/fisiología , Oxidación-Reducción , Resistencia Física/fisiología , Reacción en Cadena de la Polimerasa , Carrera/fisiología , Canal Liberador de Calcio Receptor de Rianodina/genéticaRESUMEN
Recent studies suggest a link between exercise-induced rhabdomyolysis and mutations of the ryanodine receptor (RYR1) associated with malignant hyperthermia (MH). We hypothesized that MH-susceptible mice (RYR1Y522S/wt) would exhibit greater anterior crural muscle [tibialis anterior (TA) and extensor digitorum longus (EDL) muscles] damage and strength deficits following the performance of a single or repeated bouts of eccentric contractions compared with wild-type (WT) mice. After a single injury bout, RYR1Y522S/wt mice produced more isometric torque than WT mice immediately and 3 and 7 days postinjury. Moreover, EDL muscle isometric specific force deficits were fully recovered for RYR1Y522S/wt but not WT mice 14 days postinjury. The percentage of fibers in TA muscle exhibiting signs of muscle damage 7 and 14 days postinjury were at least three times less in RYR1Y522S/wt than in WT mice. Uninjured and injured EDL muscle from RYR1Y522S/wt mice also displayed greater S-glutathionylation of RYR1 than that from WT mice. During the weekly injury bouts, torque production by RYR1Y522S/wt mice was fully recovered before the third and fourth injury bouts, whereas torque was still reduced for WT mice. Three days after multiple injury bouts, there were approximately 50% fewer fibers exhibiting signs of muscle damage in RYR1Y522S/wt than in WT TA muscle. These findings indicate that the RYR1Y522S/wt mutation protects skeletal muscle from exercise-induced muscle injury and do not support a direct association between MH susceptibility and contraction-induced rhabdomyolysis when core temperature is maintained at lower physiological temperatures during exercise.
Asunto(s)
Contracción Isométrica , Hipertermia Maligna/fisiopatología , Fuerza Muscular , Músculo Esquelético/fisiopatología , Rabdomiólisis/prevención & control , Canal Liberador de Calcio Receptor de Rianodina/metabolismo , Animales , Cafeína/farmacología , Relación Dosis-Respuesta a Droga , Estimulación Eléctrica , Glutatión/metabolismo , Contracción Isométrica/efectos de los fármacos , Hipertermia Maligna/complicaciones , Hipertermia Maligna/metabolismo , Ratones , Ratones Mutantes , Fuerza Muscular/efectos de los fármacos , Músculo Esquelético/efectos de los fármacos , Músculo Esquelético/metabolismo , Músculo Esquelético/patología , Mutación , Oxidación-Reducción , Fenotipo , Rabdomiólisis/etiología , Rabdomiólisis/metabolismo , Rabdomiólisis/fisiopatología , Canal Liberador de Calcio Receptor de Rianodina/genética , Factores de Tiempo , TorqueRESUMEN
Strength deficits associated with eccentric contraction-induced muscle injury stem, in part, from excitation-contraction uncoupling. FKBP12 is a 12-kDa binding protein known to bind to the skeletal muscle sarcoplasmic reticulum Ca2+ release channel [ryanodine receptor (RyR1)] and plays an important role in excitation-contraction coupling. To assess the effects of FKBP12 deficiency on muscle injury and recovery, we measured anterior crural muscle (tibialis anterior and extensor digitorum longus muscles) strength in skeletal muscle-specific FKBP12-deficient and wild-type (WT) mice before and after a single bout of 150 eccentric contractions, as well as before and after the performance of six injury bouts. Histological damage of the tibialis anterior muscle was assessed after injury. Body weight and peak isometric and eccentric torques were lower in FKBP12-deficient mice compared with WT mice. There were no differences between FKBP12-deficient and WT mice in preinjury peak isometric and eccentric torques when normalized to body weight, and no differences in the relative decreases in eccentric torque with a single or multiple injury bouts. After a single injury bout, FKBP12-deficient mice had less initial strength deficits and recovered faster (especially females) than WT mice, despite no differences in the degree of histological damage. After multiple injury bouts, FKBP12-deficient mice recovered muscle strength faster than WT mice and exhibited significantly less histological muscle damage than WT mice. In summary, FKBP12 deficiency results in less initial strength deficits and enhanced recovery from single (especially females) and repeated bouts of injury than WT mice.
Asunto(s)
Fuerza Muscular/genética , Fuerza Muscular/fisiología , Músculo Esquelético/lesiones , Proteína 1A de Unión a Tacrolimus/deficiencia , Proteína 1A de Unión a Tacrolimus/genética , Animales , Peso Corporal/fisiología , Cafeína/farmacología , Estimulantes del Sistema Nervioso Central/farmacología , Estimulación Eléctrica , Femenino , Contracción Isométrica , Masculino , Ratones , Ratones Noqueados , Contracción Muscular/fisiología , Músculo Esquelético/anatomía & histología , Tamaño de los Órganos/fisiología , Caracteres SexualesRESUMEN
Site-directed spin labeling EPR (SDSL-EPR) was used to determine the structure of the inhibitory region of TnI in the intact cardiac troponin ternary complex. Maeda and collaborators have modeled the inhibitory region of TnI (skeletal 96-112: the structural motif that communicates the Ca(2+) signal to actin) as a kinked alpha-helix [Vassylyev, D., Takeda, S., Wakatsuki, S., Maeda, K. & Maeda, Y. (1998) Proc. Natl. Acad. Sci. USA 95, 4847-4852), whereas Trewhella and collaborators have proposed the same region to be a flexible beta-hairpin [Tung, C. S., Wall, M. E., Gallagher, S. C. & Trewhella, J. (2000) Protein Sci. 9, 1312-1326]. To distinguish between the two models, residues 129-145 of cardiac TnI were mutated sequentially to cysteines and labeled with the extrinsic spin probe, MTSSL. Sequence-dependent solvent accessibility was measured as a change in power saturation of the spin probe in the presence of the relaxation agent. In the ternary complex, the 129-137 region followed a pattern characteristic of a regular 3.6 residues/turn alpha-helix. The following region, residues 138-145, showed no regular pattern in solvent accessibility. Measurements of 4 intradomain distances within the inhibitory sequence, using dipolar EPR, were consistent with an alpha-helical structure. The difference in side-chain mobility between the ternary (C.I.T) and binary (C.I) complexes revealed a region of interaction of TnT located at the N-terminal end of the inhibitory sequence, residues 130-135. The above findings for the troponin complex in solution do not support either of the computational models of the binary complex; however, they are in very good agreement with a preliminary report of the x-ray structure of the cardiac ternary complex [Takeda, S. Yamashita, A., Maeda, K. & Maeda, Y. (2002) Biophys. J. 82, 832].