Eccentric contractions do not induce rhabdomyolysis in malignant hyperthermia susceptible mice

Abstract

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.

Fig. 1.

Malignant hyperthermia-susceptible (RYR1^Y522S/wt) and wild-type (WT) basic contractile phenotype. In vivo torque produced by uninjured anterior crural muscles was measured as a function of stimulation frequency (A) and normalized to peak tetanic torque (B). Representative 20-Hz twitch (C) and 300-Hz peak tetanic (D) in vivo torque responses are shown. In vitro specific force produced by uninjured extensor digitorum longus (EDL) muscle was measured as a function of stimulation frequency (E) and normalized to peak specific force (F). Values in A, B, E, and F are means ± SE. *P < 0.05, RYR1^Y522S/wt vs. WT mice.

Fig. 2.

In vivo isometric torque normalized to body weight as a function of stimulation frequency produced by the anterior crural muscles of RYR1^Y522S/wt (A) and WT mice (B) before (preinjury), immediately after (immediate post), and 3, 7, and 14 days after (d post) a single bout of eccentric contractions. Values are means ± SE.

Fig. 3.

In vitro contracture force as a function of caffeine concentration produced by uninjured (A) and injured RYR1^Y522S/wt (B) and WT EDL muscle (C). Dashed lines in B and C are repeated from A for reference. Values are means ± SE. *P < 0.05, RYR1^Y522S/wt vs. WT mice.

Fig. 4.

Histological presence of tibialis anterior (TA) muscle fiber damage. TA muscle collected from RYR1^Y522S/wt (A, C, E, G) and WT mice (B, D, F, H) before injury (uninjured; A and B) or at 3 (C and D), 7 (E and F), or 14 days (G and H) after a single injury bout were stained with hematoxylin and eosin.

Fig. 5.

TA muscle active fiber degeneration and regeneration from RYR1^Y522S/wt (A) and WT mice (B). Values are means ± SE. *P < 0.05, RYR1^Y522S/wt vs. WT mice.

Fig. 6.

Ryanodine receptor (RYR1) S-glutathionylation in EDL muscle from RYR1^Y522S/wt and WT mice. Injured muscle samples were collected either 3 or 14 days after the performance of a single bout of eccentric contractions. Values are means ± SE. *P < 0.05, RYR1^Y522S/wt vs. WT mice.

Fig. 7.

Peak in vivo eccentric torque produced by the anterior crural muscles from RYR1^Y522S/wt (A) and WT mice (B) during 4 weekly injury bouts. Values are means ± SE.

Fig. 8.

In vivo isometric torque normalized to body weight as a function of stimulation frequency produced by the anterior crural muscles of RYR1^Y522S/wt (A and C) and WT mice (B and D) before (A and B) and immediately after (C and D) 4 weekly bouts of eccentric contractions. Values are means ± SE.