Identification of halothane gene carriers by use of in vivo 31P nuclear magnetic resonance spectroscopy in pigs.

In vivo muscle 31P nuclear magnetic resonance spectroscopy was performed on 12 homozygous halothane-nonsensitive female pigs and 13 female pigs heterozygous with respect to the halothane gene. Fifteen female pigs of a third line, consisting of heterozygotes and halothane-nonsensitive homozygotes, were also available. Body weight ranged from 12 to 18 kg. Mean decrease in phosphocreatine concentration in the biceps femoris of anesthetized pigs was significantly lower for heterozygous vs homozygous pigs (3.46% vs 5.94%, P less than 0.01) after 40 minutes of halothane exposure (3%; oxygen flow, 3 L/min). Also, a statistically significant difference, with respect to the initial (7.21 vs 7.11, P less than 0.008) and end muscle pH values (7.18 vs 7.06, P less than 0.0002), was observed for homozygous vs heterozygous pigs. By means of canonical discriminant analysis, it was possible to distinguish nonsensitive homozygotes from heterozygotes (P less than 0.0001). When applying this classification method to pigs of the same strain, 2 populations (nonsensitive homozygotes, heterozygotes) emerged, with a proportion of pigs corresponding to the expected value on the basis of breeding records. In contrast to the phenotypic expression of muscular rigidity related to the malignant hyperthermia syndrome, the expression of metabolic variables (phosphocreatine, pH) was shown to be dominant.