Monoamine Oxidase and the Enzymes of Ethanol Metabolism in Rats After Administration of Tetrahydroisoquinolines
A mixture of tetrahydroisoquinolines, synthesized by the method of Osswald et al. (1975), was injected intraperitoneally at a dose of 2 mg/kg into rats. After 3 hours, the activity of ethanol-metabolizing enzymes (alcohol dehydrogenase and the microsomal ethanol oxidizing system) and acetaldehyde-metabolizing enzymes (NAD- and NADP-dependent aldehyde dehydrogenases) in liver subcellular fractions, as well as the activity of monoamine oxidase with noradrenaline, tyramine, benzylamine and serotonin as substrates, were investigated in various brain areas. There was observed a decrease in the activity of the microsomal ethanol-oxidizing system and the NAD-dependent mitochondrial aldehyde dehydrogenase with low Km for acetaldehyde, the activity of the other enzymes investigated being invariable. The inhibition of the activity of monoamine oxidase with noradrenaline as a substrate was revealed in the caudate nucleus, cerebellum, truncus cerebri, and cerebral cortex, while only in the cerebral cortex was there revealed an inhibition of monoamine oxidase with the other substrates. The data obtained indicate that tetrahydroisoquinoline alkaloids not only disturb biogenic amine metabolism, but also affect ethanol and acetaldehyde metabolism in animals.
KeywordsAlcohol Dehydrogenase Monoamine Oxidase Amine Oxidase Ethanol Metabolism Infrared Spectrophotometry
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