La detection du metabolite triglutathione-chlorothalonil dans les foies de poissons suite a une exposition aigue au chlorothalonil et son utilisation comme outil dans l'investigation des mortalites aigues de poissons

Previous unpublished studies have shown that no trace of chlorothalonil (TPN) parent compound can be detected in fish exposed to a lethal dose of chlorothalonil. Some studies have shown that TPN is immediately and effectively metabolized by the fish into a triglutathione-chlorothalonil (triGS-TPN) metabolite. This metabolite has however never been quantified.;The objective of this study was to develop a method for the chemical analysis of triGS-TPN, one of main metabolite found in fish exposed to TPN. We then examined the relationship between the TPN concentration in water and the concentration of triGS-TPN found in the liver of fish exposed to TPN.;The analytical method was developed by using a triGS-TPN standard which we synthesized. The triGS-TPN is not available on the market, therefore the product was synthesized using the biochemical reaction between TPN and glutathione. The triGS-TPN was then extracted and purified by solid phase extraction. The analyses were performed by HPLC-MS, using a modified version of the Ronser et al. 1996 method.;The results of a first toxicity test have shown that when fish died as a result of an acute exposure to varying lethal concentrations of TPN, concentrations of triGS-TPN in the livers of fish leveled off, showing no significant difference (ANOVA, p>0.05). However there was a significant difference (ANOVA, p<0.001) between the concentration of triGS-TPN in livers of fish exposed to sublethal concentrations of TPN and the concentration of triGS-TPN in livers of fish that died from an exposure to lethal concentrations of TPN.;We have also studied the effect of decay in fish tissue on the concentration of the triGS-TPN metabolite in fish liver. We have found that there was a significant loss (65%, ANOVA p<0.01) of triGS-TPN after 24h. After 72h of tissue decay, no trace of triGS-TPN could be found in the fish liver.;Fish samples from reported fish kill events that occurred in 2002 and 2007 in Prince Edward Island, Canada were analyzed for triGS-TPN. Low concentrations of the triGS-TPN metabolite were detected in some of the fish livers indicating an exposure to TPN. However, tissue decay prevents us from clearly establishing the link between the death of the fish and TPN exposure. This study reveals the importance of prompt sampling after fish kill events.;The results of this study show the importance of considering physiological metabolites and degradation metabolites in environmental analysis and their use as a diagnostic tool for environmental disasters.