Hydroxyl-radical production and ethanol oxidation by liver microsomes isolated from ethanol-treated rats.
In order to distinguish between the mechanism of microsomal ethanol oxidation and hydroxyl-radical formation, the rate of cytochrome P-450 (P-450)-dependent oxidation of dimethyl sulphoxide (Me2SO) was determined in the presence and in the absence of iron-chelating compounds, in liver microsomes from control, ethanol- and phenobarbital-treated rats. Ethanol treatment resulted in a specific increase (3-fold) of the microsomal ethanol oxidation and NADPH consumption per nmol of P-450. A form of P-450 was purified to apparent homogeneity from the ethanol-treated rats and characterized with respect of amino acid composition and N-terminal amino acid sequence. Specific ethanol induction of a cytochrome P-450 species having a catalytic-centre activity of 20/min for ethanol and consuming 30 nmol of NADPH/min could account for the results observed with microsomes. Phenobarbital treatment caused 50% decrease in the rate of ethanol oxidation and NADPH oxidation per nmol of P-450. The rate of oxidation of the hydroxyl-radical scavenger Me2SO was increased 3-fold by ethanol or phenobarbital treatment when expressed on a per-mg-of-microsomal-protein basis, but the rate of Me2SO oxidation expressed on a per-nmol-of-P-450 basis was unchanged. Addition of iron-chelating agents to the three different types of microsomal preparations caused an 'uncoupling' of the electron-transport chain accompanied by a 4-fold increase of the rate of Me2SO oxidation. It is concluded that ethanol treatment results in the induction of P-450 forms specifically effective in ethanol oxidation and NADPH oxidation, but not in hydroxyl-radical production, as detected by the oxidation of Me2SO.
D000818:Animals; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D004121:Dimethyl Sulfoxide / Q000378:metabolism; D000431:Ethanol / Q000378:metabolism* / Q000494:pharmacology; D005609:Free Radicals; D006878:Hydroxides / Q000378:metabolism*; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects / Q000378:metabolism*; D009249:NADP / Q000378:metabolism; D009251:NADPH-Ferrihemoprotein Reductase / Q000378:metabolism; D010084:Oxidation-Reduction; D010634:Phenobarbital / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains
D005609:Free Radicals; D006878:Hydroxides; D000431:Ethanol; D009249:NADP; D003577:Cytochrome P-450 Enzyme System; D009251:NADPH-Ferrihemoprotein Reductase; D004121:Dimethyl Sulfoxide; D010634:Phenobarbital