Abstract

1,1,2,3,3,3-Hexafluoropropyl methyl ether is developed as an alternative to replace ozone-depleting chlorofluorocarbons. The metabolism of 1,1,2,3,3,3-hexafluoropropyl methyl ether was studied in rat and human liver microsomes and in rats in vivo. Rat and human liver microsomes metabolized 1,1,2,3,3,3-hexafluoropropyl methyl ether to inorganic fluoride and formaldehyde in a ratio of 2:1. 2,3,3,3-Tetrafluoropropionic acid was also identified as a metabolite by GC/MS and 19F-NMR. In rat liver microsomes, formation of inorganic fluoride and formaldehyde from 1,1,2,3,3,3-hexafluoropropyl methyl ether was dependent on the presence of NADPH, time, substrate concentration and protein concentration, and was linear for up to 35 min. Microsomes from unpretreated rats oxidized 1,1,2,3,3,3-hexafluoropropyl methyl ether at low rates (3.56 nmol fluoride.20 min-1.mg-1). Pretreatment of rats with pyridine and ethanol, inducers of cytochrome P450 2E1, increased the rate of fluoride formation. The rates of fluoride formation from 1,1,2,3,3,3-hexafluoropropyl methyl ether correlated well with the relative amount of cytochrome P450 2E1 in the microsomes as quantified by immunoblotting. Coincubation of 1,1,2,3,3,3-hexafluoropropyl methyl ether with microsomes and diethyldithiocarbamate (100 microM), an inhibitor of cytochrome P450 2E1, reduced fluoride production by > 80%. In different samples of human liver microsomes, rates of fluoride formation were higher than observed in liver microsomes from unpretreated rats and correlated well to the content of cytochrome P450 2E1 protein as determined by immunoblotting and chlorzoxazone 6-hydroxylation.(ABSTRACT TRUNCATED AT 250 WORDS)