3-Methyl-4-nitrophenol metabolism by uridine diphosphate glucuronosyltransferase and sulfotransferase in liver microsomes of mice, rats, and Japanese quail (Coturnix japonica)

3-Methyl-4-nitrophenol (PNMC) is a component of diesel exhaust particles and one of the major breakdown products of the insecticide fenitrothion. This chemical has a high potential for reproductive toxicity in Japanese quail (Coturnix japonica) and rats. Because PNMC inhaled by the body is metabolized by uridine diphosphate glucuronosyltransferase (UGT) and sulfotransferase, we investigated these enzyme activities in the hepatic microsomes and cytosols of quail (as a model of wild birds) and compared these activities with those of rats and mice as models of ecological and human risk assessment. The maximum velocity of the UGT for PNMC in quail was 12.7 nmol/min/mg, which was one third and one fourth those of rats and mice, respectively. The Michaelis-Menten constant of UGT for PNMC in quail was 0.29 mM, which was 1.3- and 1.8-fold higher than that in mice and rats, respectively, but not significantly different. In accordance with these results, UGT activities for PNMC were lowest in quail, with those in mice and rats being 4.4- and 2.7-fold higher, respectively. Sulfotransferase activity for PNMC was considerably less than that of UGT in all animals, including quail; no significant differences in the activities were found among mice, rats, and quail. These results suggest that glucuronidation may be involved primarily in PNMC elimination from wild birds as well as mammals and that the UGT activity in quail is less than that in the rodents.