An Assessment Of Early Toxic Effects Of TBT On Rats By Multi-biomarkers

Tributyltin(TBT) is a kind of widely used organotin mainly in wood preservation, PVC plastic heat-stabilizer and disinfection of industrial circulating cooling waters. The most important application of TBT is as antifouling agent in paints used on vessels and marine buildings to prevent the adhering of mollusks, which decrease the velocity of vessels. As a result, the lifetime of vessels and marine buildings prolongs and the expense on dock repairing decreases. The production and applications of TBT are increasing due to its vast economical benefits.But the harm of TBT to environment especially marine environment appeared after the broad use of TBT. TBT is not only toxic to target marine organisms but also to other aquatic organisms. Immunotoxicity, reproductive toxicity, neurotoxicity and cytotoxicity induced by TBT have been extensively reported in recent years. Many researches founded that inducing apoptosis is one of the important mechanisms of the toxic effect of TBT.Due to the lower degradation, TBT can last long period in environment. Therefore, the problems caused by application of TBT like reduction of the yield of seafood, harmfulness to high animals or human being by contaminated seafood through food chain, are still highly concerned. Even though the resolution to forbid the usage of TBT in vessels from Jan.1, 2003 has been confirmed by International Marine Organization (IMO). There are many reports on the toxicity of TBT to marine organisms, but few about mammals. So SD rats were used as experimental animals in this study. Multi-biomarkers are adopted which are relative to antioxidant system andoxidative damages. The aim of this study is investigate the early toxic effects of TBT to rats by multi-biomarkers, the relativity of the markers and time/dose-effects. The purpose is to provide helpful information in appraising the general toxic effects of TBT to mammals through this study.Forty-eight Sprague-Dawley rats were divided into five groups randomly. The rats were gavaged for 11 consecutive days with TBT of 0, 0.1, 1.0 and 10.0 mg/kg B.W, respectively. The animals were sacrificed on the forth, eighth and twelfth day of the treatment. The activities of SOD, GST and GR and contents of MDA in liver, the activities of AChE in brain, DNA damage of lymphocytes and organ/weight values were analyzed.The results were shown as below:1. The activities of SOD increase significantly in the fourth day and has no change in eighth and twelfth day of TBT exposure.2. The contents of MDA has no change in fourth and twelfth day, increases significantly in the eighth day. It indicates the presence of lipid peroxidation in liver.3. Lymphocytes' tail length and tail moment have significantly increases with the elevation of TBT dosage and have a good dose-effect relationship. There is a good relationship between lymphocytes' tail length and tail moment. It indicates the strong damage of TBT to DNA of rats' lymphocytes.4. The activities of AChE in brain increase significantly in the forth, eighth and twelfth day. Further research is needed to reveal the causal relation between the change of AChE and biological effects.5. Brain/weight value increases and then decreases with the increasing of TBT doses in fourth day, and that in 1.0 mg/Kg.d dosage group has significant difference to the control. It has a decreasing trend in eighth day and there is a significant difference between the highest dosage group to the control group.6. The activities of phase II enzyme of detoxification system GST increase in fourth day with the elevation of TBT exposure dosage and have no significant difference in eighth and twelfth day. The activities of antioxidant enzyme GR have no significant difference with TBT exposure dosage and duration.Conclusions:1. The changes of activities of SOD and the content of MDA have negative correlation in fourth and eighth day, which indicate the presence of protection of SOD against oxidative damage induced by TBT.2. Both the lipid peroxidation (MDA) and the breakage of DNA strand (Comet assay) are biomarkers...