Cytochrome P450 dependent free radical processes in the liver microsomes of rats administered diethyl phthalate

Diethyl phthalate (DEP) is widely used as a plasticizer and aromatic additive in various consumer products. Biotransformation of this xenobiotic occurs through the cytochrome P450 (CYP) -hydroxylating system, the catalytic cycle of which is accompanied by ROS generation in uncoupling reactions. The present study investigated the effects of DEP administration on the CYP-dependent ROS generation and lipid peroxidation in the rat liver microsomes. The experiment was conducted on three groups of purebred white rats: control (intact animals); rats orally administered with DEP at a dose of 2.5 or 5.4 mg/kg b.w per day for 21 days. CYP-mediated ROS generation was initiated by adding 0.24 μmol/l NADPH to the incubation mixture. It was found that daily administration of DEP at a dose of 2.5 mg/kg led to an increase in the rate of O2•– formation, H2O2 content, and intensification of lipid peroxidation in the liver microsomes only on the 21st day of the experiment. In contrast, administration of DEP at a dose of 5.4 mg/kg resulted in increased content of primary, secondary and final lipid peroxidation products as early as on the 14th day of xenobiotic exposure, indicating a dose- and time-dependent effect of DEP on the oxidative stress intensity in liver microsomes. Keywords: diethyl phthalate, hydrogen peroxide, lipid peroxidation, liver microsomes, superoxide radical