Effect of prior exercise on thermal sensitivity of malignant hyperthermia-susceptible muscle

Abstract

Malignant hyperthermia (MH) episodes may occur upon exposure to halogenated anesthetics, during resistance and endurance exercise, and in response to thermal stress. The purpose of this study was to investigate the effects of prior eccentric and concentric (i.e., wheel running) exercise on the thermal sensitivity of isolated MH-susceptible mouse muscle (RyR1(Y522S/wt)). Eccentric, but not concentric, exercise attenuated the thermal sensitivity of MH-susceptible muscle.

Figure 1

Effects of prior exercise on temperature sensitivity and functional capacity of MH susceptible muscle. (a) The total tension produced over the 30-minute incubation periods (i.e., resting tension integral) were compared between WT (top panel) and RYR1^Y522S/wt (bottom panel) mice and among conditions. See methods section for definition of groups. There were no significant differences between WT and RYR1^Y522S/wt values for any condition at 30°C, while only E-0d and E-3d values were similar (†) between genotypes at 35°C. (b) Peak isometric specific force of WT and RYR1^Y522S/wt muscle produced at 35°C, expressed as a ratio of force produced at 30°C, was compared between genotypes and among conditions. (c) Caffeine contracture force for WT and RYR1^Y522S/wt muscle produced at 35°C. * denotes a significant main effect of genotype (p < 0.001). (d) JP1:Tubulin values for WT and RYR1^Y522S/wt tibialis anterior muscles. Within each panel, values with different letters are significantly different (p < 0.05). All values are expressed as means ± SEM; sample sizes (n) are similar for (a & b).