1-Chloro-2-hydroxypropane epoxidase in rat liver and other organs

1,2-Dichloropropane, a widely used solvent for paint and varnish, is metabolized by the rat liver microsomal system to give a hydroxyl metabolite which is then epoxidized. The present study reports on a method for determining 1-chloro-2-hydroxypropane epoxidase and its distribution in several organs in rats. 10000xg supernatants from 20% w/v homogenates (0.1 ml) were incubated with 0.3 ml of a cofactor mixture (0.08 µmol NADP, 1.5 µmol glucose-6-phosphate, 7.8 µmol niacinamide and 3.9 µmol MgCl2 in phosphate buffer 0.1 M, pH 7.4) and 0.1 ml of substrate (0.01 M). After incubation for 30 min at 37°C, formation of propylene glycol was measured according to Harger & Forney. Enzyme activities (nmol-1 mg protein-1, mean±SD) were as follows: liver 2.84±0.61; kidney cortex 8.50±1.22; testis 8.41±2.19; lung 4.61±1.15. These results support our previous report that the solvent has a greater toxic effect on the kidney. This may be due to the higher epoxide formation during the metabolism of the solvent.