The activity of several antioxidant and detoxifying enzymes, superoxide dismutase SOD, GSH peroxidase GSHPx, GSSG reductase GSR and GSH S transferase GST, the contents of thiobarbituric acid reactive substances TBARS, and the SOD and GST isoenzyme patterns were studied in the livers of chubs Leuciscus cephalus from reference river areas and polluted urban sites. Livers of polluted fish contained higher concentrations of transition metals, especially copper and iron. Total GSHPx activity was 1.8 fold higher in the polluted fish than in reference animals, while the SOD and GSR activities and the TBARS content were not significantly changed. Three new SOD isoforms pI 4.45, 5.1, 5.2 and a higher intensity of the band pI 4.2 were observed after isoelectrofocusing of polluted fish extracts. Total GST activity was higher in fish from polluted areas. The GST isoenzyme pattern was studied using subunit specific substrates DCNB, EPNP, EA, NPB, NBC and by Western blot using antibodies specific to rat GST subunits 1, 8 Alpha class, 3 Mu class and 7 Pi class. Reference and polluted fish lacked cross reactivity towards Alpha class GSTs. Reference fish displayed weaker cross reactivity towards CST 7 and 2.3 fold lower activity with EA, while higher cross reaction with GST 3 was observed in polluted fish.

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Studies were undertaken to investigate the activity response of the antioxidant enzymes superoxide dismutase (SOD), glutathione peroxidase (GSHPx), glutathione reductase (GR) and mercury reductase (MR) of rumen bacteria Streptococcus bovis and Selenomonas ruminantium following exposure to HgCl2. SOD activity of S. bovis which was considered as Mn‐SOD increased when incubated with 5 μg Hg2+ ml−1 in anaerobic or aerobic conditions. A significant increase in the aerobic activities of GSHPx, GR and MR was observed in the presence of Hg2+. The anaerobic activities of these enzymes were unchanged and increased production of thiobarbituric acid reactive substances was observed. S. ruminantium was tolerant to 10 times higher concentrations of Hg2+ than S. bovis. As a reduction of GSHPx, GR and MR activities after exposure to Hg2+ was observed, we assume that the production of sulfides prevented the toxic effect of mercury on this bacterium.

The effects of feed supplementation with anorganic and organic forms of Se on the activities of liver enzymes, glutathione peroxidase (cGPx) and superoxide dismutase (SOD), was examined in young growing chickens. The birds were divided to 4 groups on the day of hatching. The first group received the basic diet (BD) with a Se content 0.12 mg.kg -1 of dry matter (DM) only. Diets for groups 2, 3 and 4 consisted of BD supplemented with sodium selenite, 0.2 mg·kg -1 of DM; Se-enriched yeast, 0.2 and 0.7 mg·kg -1 of DM, respectively. Analysis of the liver tissue from 2-and 4-week-old chickens showed no effects of the various Se intake or effects of the form supplemented to the diet on cGPx activity. The 2-week-old birds showed no significant effects of diets on SOD activity in the liver tissue. On the other hand, liver SOD activity appeared to be dose-dependent in 4-week-old chickens, but no effects of the form of Se applied were found. Lipid peroxide formation measured as the appearance of thiobarbituric acid-reactive substances (TBARS) showed no dependence on the amount or form of Se supplemented to the ration, but its content in the liver of 4-week-old chickens was higher than in the 2-week-old ones. The selenium level in the liver tissue was clearly related to its contents in the feeds, but no effects of the form of selenium supplemented on this parameter were noticed after 2 or 4 weeks of dietary intake. The presented results suggest that dietary supplementation with Seyeast to a level reaching even 0.7 mg·kg -1 of DM does not induce oxidative stress in young growing chickens. The synthesis of liver cGPx of 2-to 4-week-old chickens of a laying strain already seemed to be saturated at a dietary intake of Se at a level of 0.1 mg·kg -1 of DM.

The activities of the antioxidant and detoxifying enzymes, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSHPx), glutathione reductase (GR), glutathione-S-transferase (GST), and the content of thiobarbituric acid reactive substances (TBARS) were determined in the liver and kidney of rabbits after exposure to bendiocarb. In the liver, the activities of SOD, CAT and GR were not affected by bendiocarb. The induction or inhibition of isoenzymes of SOD (mainly MnSOD) were observed in the experimental groups. The activities of GSHPx-cum and GSHPx-H2O2 significantly decreased on the days 3 and 10 of the experiment. The activity of GST significantly increased on the day 9 of the experiment. In the kidney, the activity of SOD was significantly increased and the new MnSOD isoenzymes were detected. The activities of CAT and GSHPx-H2O2 were significantly decreased in the experimental groups. The activity of GR significantly increased on days 3 and 10, and the activity of GST was significantly increased on days 3, 10, and 30. Exposure of rabbit to bendiocarb did not affect the content of TBARS in the kidney. In the liver, the content of TBARS was significantly increased in the experimental groups as compared to the control. Our results showed that the response of organs to bendiocarb is different and may depend on the specific organ damage and their protective abilities. The alterations in the activities of the antioxidant defence system, increased TBARS values, and changes in the SOD isoenzyme pattern showed that the toxic effect of bendiocarb is not only in the acetylcholine esterase inhibition, but also in ROS production.