Abstract
A and B-form monoamine oxidase (MAO) activities were measured in the liver of rats maintained with a diet containing 0.06% 3'-methyl-4-dimethylaminoazobenzene (3'-Me-DAB). A-form MAO activity was similar to the control value throughout the feeding periods with serotonin as substrate. In contrast, B-form MAO activity decreased rapidly and the level of MAO activity was maintained at about 30% with β-phenylethylamine (β-PEA) as substrate. 3'-Me-DAB feeding did not cause any changes in MAO activity in the brain of rats. A single administration of 3'-Me-DAB (100 mg/kg p.o.) failed to alter A and B-form MAO activities for up to 4 days after its administration. The mechanism of inhibition of B-form MAO activity in rat liver mitochondria by 3'-Me-DAB was investigated. The inhibition of 3'-Me-DAB of B-form MAO activity, in vitro, was competitive and reversible. There was no difference in the apparent Michaelis constant toward β-PEA between control and 3'-Me-DAB fed rats. B-form MAO in rat liver mitochondria was titrated with (−)deprenyl; this compound is selective to and an irreversible inhibitor of B-form MAO. The content of B-form MAO in liver mitochondria of rats fed 3'-Me-DAB for 3 weeks was decreased to about 60% of the control level.
Published Version
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