Cytochrome P450 reductase-mediated anaerobic biotransformation of ethanol to 1-hydroxyethyl-free radicals and acetaldehyde

The ability of cytochrome P450 reductase to metabolize ethanol (EtOH) to ac etaldehyde (AC) and 1-hydroxyethyl free radicals (1HEt) in anaerobic media was studied. Determination of AC was made by GC-FID analysis of the head sp ace of incubation mixtures. The formation of 1HEt was established by GC-MS analysis of the adduct formed between the: radical and the spin trap PEN. R esults showed that pure human P450 reductase is able to biotransform EtOH t o AC and 1HEt in a NADPH-dependent process under an oxygen-free nitrogen at mosphere. Pure FAD in the presence of NADPH was also able to generate AC an d 1HEt fi om the alcohol. Anaerobic incubation mixtures containing either r at liver microsomes or pure nuclei were also able to biotransform EtOH to A C and 1HEt in the presence of NADPH. These processes were inhibited by anti body against rat liver microsomal P450 reductase. Results suggest that semi quinone forms of the flavin in P450 reductase may biotransform EtOH. These reactions might be of some significance in tissues where the P450 reductase is present in the absence of specific forms of cytochrome P450 known to be involved in EtOH metabolism (e.g. CYP2E1). However the toxicological signi ficance of this enzymatic process remains to be established. (C) 2000 Elsev ier Science Ireland Ltd. All rights reserved.