Single-dose ethanol administration to rats caused inhibition of liver mitochondrial monoamine oxidases (MAO) A and B, and an increase in susceptibility of MAO A (but not MAO B) to limited proteolysis. Chronic ethanol feeding resulted in a less distinct alteration in catalytic activity and susceptibility to proteolysis of mitochondrial MAO, but increased the amount of soluble MAO. The sensitivity of membrane-bound MAO to inhibitors (imipramine and chlorpromazine), action of which depends on their lipophilicity and/or hydrophobicity, remained unchanged, compared with controls. Increased amounts of soluble MAO seen after chronic ethanol feeding probably reflect an impairment of insertion of newly synthesized enzyme molecules into the outer mitochondrial membrane, rather than solubilization of MAO from it.
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