It is well known that environmental contaminants such as arsenic can induce oxidative stress in fish. It is also known that thyroid hormone status affects susceptibility to oxidative stress. However, the effect of thyroid hormone status on pollutant- induced oxidative stress is unknown. This is significant, because such knowledge would help to assess the risk of xenobiotics such as arsenate, a prevalent contaminant in the environment. The interaction between arsenate- induced oxidative stress and altered thyroid hormones has not been elucidated thoroughly in previous studies. In order to address this, we used zebrafish (Danio rerio). There are many advantages of using this as a research model over rodents such as rats. For example, it is often used to study the effects of xenobiotic compounds such as arsenic. This xenobiotic is widespread in the environment due to human activities such as agricultural, industrial and military activities. For this purpose, it is more appropriate to use this fish as a research model. The reason for using the chemicals perchlorate and arsenic is that they occur together in the environment. Oxidative stress can be caused by environmental pollutants such as arsenic. One of the key defenses against oxidative stress is glutathione (GSH). GSH concentrations, GSSG/GSH ratios, and lipid peroxidation (TBARS) were used to assess the affect of arsenic, perchlorate and thyroxine (T4) on zebrafish (Danio rerio) liver, gills, and muscle tissue. Our results support the hypothesis that thyroid hormones modulates the toxicity of arsenic. Moreover, arsenite was found to cause oxidative stress as reflected by GSH levels, GSSG/GSH levels, and lipid peroxidation (TBARS). Although hypothyroidism caused by perchlorate did not cause any major difference on oxidative stress, but hyperthyroidism caused by treating the fish with T4 enhanced GSH levels. This shows that thyroxine is involved in response to oxidative stress. In addition, perchlorate abrogated or reversed the affects of arsenite on oxidative stress parameters. These results support the hypotheses that thyroid hormones modulate oxidative stress in general, and arsenite-mediated oxidative stress in particular.
|Commitee:||Jennings, David, Williams, Jake|
|School:||Southern Illinois University at Edwardsville|
|School Location:||United States -- Illinois|
|Source:||MAI 52/04M(E), Masters Abstracts International|
|Subjects:||Molecular biology, Environmental science|
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