Eccentric contractions do not induce rhabdomyolysis in malignant hyperthermia susceptible mice

Corona BT, Rouviere C, Hamilton SL, Ingalls CP. Eccentric contractions do not induce rhabdomyolysis in malignant hyperthermia susceptible mice. J Appl Physiol 105: 1542-1553, 2008. First published September 11, 2008; doi:10.1152/japplphysiol.90926.2008. 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 (RYR1(Y522S/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, RYR1(Y522S/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 RYR1(Y522S/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 RYR1(Y522S/wt) than in WT mice. Uninjured and injured EDL muscle from RYR1(Y522S/wt) mice also displayed greater S-glutathionylation of RYR1 than that from WT mice. During the weekly injury bouts, torque production by RYR1(Y522S/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 similar to 50% fewer fibers exhibiting signs of muscle damage in RYR1(Y522S/wt) than in WT TA muscle. These findings indicate that the RYR1(Y522S/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.