Possible catabolism of paraquat in mouse brain microsomes

Whether formalin would be formed from paraquat (PQ) was studied in vitro using subcellular fractions of the mouse tissues. When Nash's method was used, a detectable increase of the OD at 412 nm was obtained only in the brain microsomal fraction in the presence of NADPH. The OD was increased by the addition of 0.1 mM EDTA. It disappeared when NADPH was omitted or when microsomes were denatured. However, when the brain microsomes were incubated with [3H]PQ in the presence of NADPH and EDTA, no [3H] formalin was detected. These results suggest that PQ may be catabolized in the mouse brain microsomes, though not demethylated, resulting in the production of the Nash reagent-reactive substance.