Experimental porcine malignant hyperthermia: macromolecular characterization of muscle plasma membranes.

The purpose of this study was to examine muscle plasmalemma which is implicated as the site responsible for the appearance of malignant hyperthermia in human and susceptible strains of animals. In pigs with malignant hyperthermia (MH) the activity of Na+/K+, Mg2+-ATPase, p-nitrophenylphosphatase and Mg2+-ATPase fell significantly during anaesthesia. In the control group the contrary occurred. In both the groups tested there was a marginal rise in the levels of sialic acid. The levels of cholesterol and lysoderivatives were abnormal before the provoking agents were administered but they changed significantly after onset of the MH syndrome. Anaesthesia reduced the phospholipids level in both tested animal groups. Before and after the provoking agents an impoverishment in the polypeptide pattern in the range between 80,000 and 30,000 daltons of mol. wt. in MH susceptible animals occurred. It is postulated that in MH the macromolecular disorganization of the muscle plasma membranes means that defence mechanisms maintaining cell gradients do not work in the presence of provoking agents.