Histochemical observations on muscle from normal and malignant hyperthermia-susceptible swine.

A comparison was made of muscle from two locations in both the longissimus and the semitendinous muscles of normal and malignant hyperthermia-susceptible swine. Serial frozen sections were stained for alkali-stable adenosine triphosphatase (ATPase), phosphorylase, and the oxidative enzymes succinate dehydrogenase and reduced nicotinamide adenine dinucleotide (NADH)-diaphorase. Myofiber types were identified on the basis of these staining reactions. There was no consistent statistically significant difference between muscle from normal and muscle from susceptible swine with any system of fiber classification. This is contrary to several published reports but consistent with physiologic studies which indicate that both oxidative and glycolytic pathways are abnormally active during the onset of malignant hyperthermia.