[Stimulation of microsomal lipid peroxidation as the effect of combined action of xylene and ethanol]

The aim of the study was to evaluate if in the case of combined exposure of rats to xylene and ethanol stimulation of lipid peroxidation in the liver microsomes (an index of interaction with lipids and derangements of integrity/fluidity of membranes) might occur. Experiments were carried out on male Wistar rats in the conditions of prolonged, inhalatory preexposure to m-xylene at concentration of 4000 mg/m3 for 6 and 12 weeks, and next joint 5-fold treatment with ethanol (2.5 g/kg oral doses in 12 hours intervals for 3 days). The degree of lipid peroxidation was assessed both in vivo and in vitro under chemical stimulation: enzymatically (NADPH, Fe2+) and nonenzymatically (ascorbic acid, Fe2+). The chemical stimulation permits to measure multiplied biological effects of chemicals acting in vivo. As a results of performed studies it was found that the highest increase of lipid peroxidation appeared in the case of prolonged, 12 weeks exposure to m-xylene (4000 mg/m3) and successively under subacute ethanol treatment and 6-week m-xylene exposure. Thus, it was evidenced that stimulation of lipid peroxidation depends on the duration of exposure to m-xylene. Stimulation of lipid peroxidation, revealed here, may arise from the processes of biotransformation of xylene in cyt. P-450 monooxygenase system where generated oxygen free radicals may attack the lipid components of microsomal membrane as well as from the mechanisms leading to decrease of antioxidant ability of the organism (decrease of glutathione-SH and vitamins E and C levels).