The study was carried out on male Wistar rats weighing 180-230 g. The rats were divided into two groups: examined - receiving oil solution of chlorfenvinphos in doses of 0.5 LD50, and 0.1 LD50, and control group - receiving oil. The activity of superoxide dismutase (SOD), catalase (CAT) and concentration of malondialdehyde (MDA) were determined after 1, 24 and 48 hours of intoxication.

We observed an increase in the liver activity of SOD in further period of intoxication with chlorfenvinphos in both doses and a decrease of liver SOD activity in the rats intoxicated with the higher dose. The CAT activity in liver of the treated rats increased at the 1st hour of experiment with a dose of 0.5 LD50 and at the Ist hour and the 24th hour after intoxication with a dose 0.1 LD50. Hepatic concentration of MDA showed a decrease at the 24th hour of intoxication with chlorfenvinphos and an increase at the 48th hour of intoxication with the higher dose and returned to control value for the rats intoxicated with the lower dose.

SOD and CAT play a major role in the maintaince of the physiological level of reactive form of oxygen. When reactive oxygen species generation exceeds capability of redox degrading systems, MDA levels increase.

The results obtained suggest that reactive oxygen species in liver injury might be caused by chlorfenvinphos.