Experimental porcine malignant hyperthermia: the activity of certain transporting enzymes and myofibrillar calcium-binding protein content in the muscle fibre.

The activity of enzymes transporting calcium across the membrane of the muscle fibre and sarcoplasmic reticulum was studied. The activity of actomyosin Mg2+-ATPase and the composition of troponin were investigated also. In seven Pietrain pigs halothane alone or with suxamethonium induced the malignant hyperthermia syndrome. In the animals with malignant hyperthermia Ca2+-ATPase was not activated in the plasma membranes of the muscle fibres, when compared with control animals (n = 4). An increase of Ca2+-ATPase of the sarcoplasmic reticulum was observed in animals with malignant hyperthermia; the opposite was noted in the control group. No significant changes in the activity of Mg2+-ATPase of the sarcoplasmic reticulum and of Mg2+-ATPase of actomyosin were observed after exposure to halothane in control pigs and those with malignant hyperthermia. The amount of troponin C was significantly changed in the animals with malignant hyperthermia. The mechanism of the development of malignant hyperthermia syndrome is discussed.