The Toxic Effects Of Atrazine On Detoxification Enzymes And DNA Damage In Zebrafish

Introduced in the 1950s, atrazine (2-chloro-4-ethylamino-6- isopropylamino-1, 3, 5-triazine) has been one of the most frequently used herbicides worldwide. In fact, agriculture runoff, irrigation waters, and wetland applications are the central sources from which this contaminant enters the aquatic environment, leading to the deterioration of water quality in the process. Especially, atrazine can be transferred through phytoplankton to fish and ultimately to humans. The issue of contamination of atrazine has increased in importance in recent years, due to its persistence within the environment. So, it is emergent to evaluate the water ecological safety of atrazine.In this dissertation, taking atrazine as a model pollutant,ecotoxicity of the pesticides was evaluated by studying its toxicity and trauma effects on Danio rerio. The liver microsomal cytochrome P450 enzymes and glutathione S- transferase (GST) activity were measured respectively. From the biochemistry aspect, toxicity effects of the pesticides on Danio rerio were evaluated. Trauma effects of atrazine on DNA were tested by using single cell gel eletrophoresis test. From molecule level, some primary discussions of the possible induced mutation were made in the experiments. The results could be summarized as follows:1. Effect of atrazine on cytochrome P450 enzymes in zebrafish liver: The liver microsomal cytochrome P450 content, NADPH-P450 reductase (NCR), aminopyrine N-demethylase (APND), and erythromycin N-demethylase (ERND) activity were measured. The results indicated that, within the range of test atrazine concentrations, either P450 content or P450 isozyme activities could be induced by atrazine; atrazine significantly stimulates cytochrome P450 enzymes in zebrafish livers at concentrations ranging from 0.01 to 1 mg/L. Moreover, gender-based differences were also observed. Our data showed that, in control zebrafish, cytochrome P450 content and NCR activity in males are 24.4% and 13.9% higher, respectively; females are more susceptible to CYP3A than males following atrazine treatment, APND and ERND levels were found to be higher in females than in males.2. Effect of atrazine on glutathione-S-transferase (GST) activity in zebrafish liver: Our present results evidence different trends in GST activity between both males and females of zebrafish. Compared to the controls, for males, the GST activity at all atrazine concentrations (0.01, 0.1, 1 mg/L) was stimulated markedly throughout the duration of the entire experiment while a significant inhibition of the activity at 1mg/L atrazine at days 5 and 20. For females, significantly increase was found at 0.1 mg/L on the days 5 and 15 while 0.01 mg/L on the day 20. Moreover, gender-based differences were also observed on GST activity.3. Effect of atrazine on DNA damage in zebrafish liver: In the single cell gel eletrophoresis test, the results showed that, Olive tail moments of Danio rerio was enhanced after treatment with different doses of atrazine on the days 5, 10, 15, 20, and 25, and DNA fragmentation showed a dose-response relationship, DNA damage increased with increasing atrazine concentrations, and significant differences were found compared to the controls.