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Objective: The aim of this study was to evaluate the chemopreventive potential of organoselenium compounds (Se I and Se II) in the well-established rat model treated with 7,12-dimethylbenz[a]anthracene (DMBA), by monitoring the extent of tyrosine hydroxylase (TH) activity, adrenomedullin (ADM) level and total RNA level in adrenal medulla. Organic pollutants are the most important environmental factor for the biologic systems. DMBA exposure appears to be associated with a number of physiological disease processes., Methods: The effects of Se I and Se II compounds were investigated on TH activity, ADM and total RNA levels in adrenal medulla of rats exposed to DMBA., Results: TH activity, ADM and total RNA levels were found to be increased significantly due to the effect of DMBA (p < 0.05). This increase was restricted in the Se I- and Se II-treated groups (p < 0.05)., Conclusion: The present data showed that the organoselenium compounds may have important effects in the maintainance of homeostasis against stress induced by DMBA.

The main purpose of this study is to discuss the effect of Cd+2, Cr+3 and Se metals on biochemical parameters in liver tissue of Oncorhynchus mykiss. The rainbow trout were exposed to heavy metal stress (Cd+2, Cr+3) at 2 ppm dosage. The present study was undertaken to determine the protective effect of selenium treatment at the same dosage (2 ppm) on some biochemical parameters. The activity of catalase (CAT), glutathione peroxidase (GSH-Px), superoxide dismutase (SOD) and the changes in levels of malondialdehyde (MDA) from biochemical parameters were determined in liver tissue of the fish groups exposed to heavy metals, especially for the selenium-applied groups. Results of this study showed that the activities of CAT, GSH-Px and SOD in the tissues of fish exposed to the stress of Cd+2 and Cr+3 were significantly lower than the control groups (P < 0.05). Meanwhile, the closer values to the control groups were obtained in selenium-added groups (Cr+3 + Se+4, Cd+2 + Se+4). For the level of MDA, the last production of lipid peroxidation showed increases (P < 0.05) in the groups exposed to the metal stress, whereas significant decreases were obtained in selenium-applied groups. The result of the statistical evaluation showed that the negative effects occurring in the biochemical parameters of the applied groups exposed to the toxicity of heavy metal were significantly eliminated (P < 0.05) as a result of selenium treatment.

Chemical toxic pollutants (especially heavy metals) are important sources of reactive oxygen species (ROS) in biological systems. Membrane phospholipids of aerobic organisms are continually subjected to oxidant challenges from endogenous and exogenous sources, while peroxidized membranes and lipid peroxidation products represent constant threats to aerobic cells. The primary antioxidant protection against free radical and ROS is provided by the enzymes glutathione peroxidase (GSH-Px), superoxide dismutase (SOD) and catalase (CAT), respectively. The trace element selenium has been implicated in chemo-prevention and drug-resistance through reduction of oxidative stress. Selenium could prevent damage to the unsaturated fatty acid of subcellular membranes by lipid peroxidation induced by free radicals. The results reported here show that sodium selenite has an important contribution to antioxidative defense for the spleen and heart of rainbow trout. The ability of sodium selenite to prevent the oxidative stress induced by heavy metals (Cd(2+), Cr(3+)) in fish was rationalized.