Characterization of swine susceptible to malignant hyperthermia by in vivo, in vitro and post-mortem techniques.

We investigated German Landrace pigs from a special breeding program producing animals which were of three genotypes with respect to in vivo halothane inhalation (i.e., exposure to 3% halothane for up to 3 min): (1) Hal NN, i.e. homozygous normal exhibiting no response; (2) Hal Nn, i.e. heterozygous, also responding with a normal reaction; and (3) Hal nn, i.e. homozygous for the 'halothane gene n' which exhibited signs of malignant hyperthemia (MH). Additional characteristics of these three groups of animals were studied using accepted methodology from the fields of animal science, clinical testing, and food science. The following characteristics of group (2) and (3) were different from those of the normal animals: 1) creatine kinase levels; 2) in vitro sensitivities of muscles to caffeine and halothane administration (contracture test) and 3) postmortem muscle properties. In humans, results of the in vitro contracture test are indicative of susceptibility to MH. In humans, MH is considered to be inherited as an autosomal dominant trait. Similarly the results of the in vitro contracture test described here also indicate that MH is inherited as an autosomal dominant trait in German Landrace swine.