Discordance and cosegregation of swine halothane susceptibility and 1843 C-T mutation of their RYR1 locus responsible for the ryanodine receptor

In two Siberian swine populations, the halothane test and PCR were used to determine the halothane susceptibility of the animals and to reveal a point mutation in their RYR1 gene, respectively. No correlations were found between the halothane susceptibility of an animal and the presence or absence of a point mutation at its RYR1 locus. However, the population changes in halothane susceptibility and the frequency of the mutation proved to be unidirectional. In the studied swine populations, the halothane-susceptible animals had no hyperthermia and the frequencies of their Hal and RYR1 genes changed similarly. These phenomena along with the phylogenesis of malignant hyperthermia and the porcine stress syndromes (PSS) in different breeds are discussed. In the populations studied, PSS is suggested to be under the polygenic control.