METABOLISM OF MONOAMINES IN MALIGNANT HYPERTHERMIA-SUSCEPTIBLE PIGS

A comparison of the monoamine oxidase activities in the hypothalamus and striatum between malignant hyperthermia-susceptible (Pietrain) and malignant hyperthermia-resistant (Landrace/Large White) pigs [a model for human malignant hyperthermia caused by halothane on suxamethonium] showed no significant difference between the 2 breeds. The concentrations of noradrenaline [norepinephrine], dopamine and their non-O-methylated metabolites did not reflect the low activities of monoamine oxidase type A differentially. The malignant hyperthermia-susceptible pigs had significantly greater concentrations of 3,4-dihydroxyphenyl glycol in the striatum and of 3,4-dihydroxymandelic acid in the hypothalamus. In the brain, low monoamine oxidase type A activity does not appear to be involved in susceptibility to malignant hyperthermia. Monoamine oxidase activities in the heart, liver, kidney and intestinal mucosa and catechol-O-methyl transferase activities in the kidney were the same in the susceptible and resistant pigs.