The effect of CO on N-, 3-, 5- and 7-hydroxylation of 2-acetamidofluorene by liver microsomal fractions from control and 3-methylcholanthrene-pretreated hamsters was studied. All hydroxylations were inhibited by CO, but the degree of inhibition was different for each hydroxylation. The ratios of CO to O2 needed for 50% inhibition of the N-, 3-, 5- and 7-hydroxylations by control preparations were 8.0:1, 8.2:1, 4.2:1 and 7.1:1 respectively and by preparations from treated animals were 4.2:1, 8.9:1, 2.3:1 and 3.2:1 respectively. These results are discussed in terms of the possible presence of more than one type of cytochrome P-450 involved in hydroxylations of 2-acetamidofluorene by liver microsomal fractions from both control and pretreated hamsters.
