[Halothane-induced malignant hyperthermia (MH) in the Belgian Landrace breed of pigs: some findings concerning the role of subcellular fractions (author's transl)].

Both calcium ++-activated magnesium++ adenosine triphosphatase and the calcium++-accumulating activity of SR isolated from white skeletal muscle of pigs of the Yorkshire breed resistant to MH and pigs of the Belgian Landrace breed susceptible to MH continue to be stable throughout the process of growth. There was not any detectable difference between the two breeds and therefore it could not be concluded that there was a defective SR membrane. Abnormal contractions induced by halothane and caffeine in biopsy specimens of muscle of MH-susceptible pigs of the Belgian Landrace breed are mainly produced by external calcium++, CN--not having any inhibitory effect in these cases. The contractions induced by combined caffeine and halothane in susceptible animals are more marked than those occurring in resistant animals. These increased contractions are mainly due to external Ca++ and, to a less extent, to CN--sensitive mitochondrial Ca++ fluxes.