TOLUENE AND P-XYLENE MIXTURE EXERTS ANTAGONISTIC EFFECT ON LIPID PEROXIDATION IN VITRO

Objectives: Previous research on a group of workers occupationally exposed to styrene, ethylene glycol, toluene, p-xylene and their mixture showed elevated levels of the main products of lipid peroxidation: malondialdehyde and 4-hydroxynonenal (MDA+,4-HNE) in plasma [1]. Moreover, an earlier in vitro study indicated a synergistic interaction between styrene and ethylene glycol on lipid peroxidation [2]. Therefore, it seemed interesting to investigate the effect of combined exposure to toluene and p-xylene on lipid peroxidation and define the type of the interaction. Materials and Methods: An in vitro model of human placenta mitochondria was used in the study. The concentration of TBARS (thiobarbituric active reagent species) was measured by spectrophotometry, and of hydroxyl radical ((OH)-O-center dot) by assessment of deoxyribose degradation. It was investigated whether the administration of coenzyme Q(10) (CoQ(10)) could have a protective function (if given before solvent exposure) or a reparatory function (if given after exposure) in solvent-induced oxidative stress. Results: Exposure to p-xylene at concentrations ranging from 5.3 to 265 mu g/ml produced an increase in TBARS concentration. The results showed that p-xylene had a stronger influence on lipid peroxidation than toluene. The mixture of toluene and p-xylene induced an antagonistic effect on lipid peroxidation, measured as TBARS concentration. The mechanism connected with (OH)-O-center dot generation was found to play an important role in the oxidative damage to lipids resulting from p-xylene exposure. Administration of coenzyme Q10 at the doses of 3.0 and 12.0 mu g/ml successfully decreased the TBARS level that was elevated after solvent exposure. Conclusions: In contrast to the synergistic effect that the mixture of styrene and ethylene glycol had on lipid peroxidation (previous study), an antagonism between toluene and p-xylene could be observed. The coenzyme Q(10) can be considered a protective agent against lipid peroxidation.