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2C (2) - Biomarkers (WE7/2) Role of B-esterases in assessing toxicity of organophosphorous pesticides and carbamates to Daphnia magna. Barata, Carlos1, Arun, Solayan1, Porte, Cinta1, 1 IIQAB-CSIC, Barcelona, Spain, Spain ABSTRACT- Acetylcholinesterase (AChE) and carboxilesterase (CbE) inhibition are used as a tool to assess exposure/effects of organophosphorous pesticides (OPs) and carbamates in aquatic crustacea. However, the dynamics of inhibition, recovery, and the physiological significance for the organism need to be thoroughly understood before their use in risk assessment programs. In this study, we exposed the cladocera Daphnia magna to environmentally relevant concentrations of OPs and carbofuran for different periods of time. Our results revealed differences in kinetics of enzyme inhibition and recovery depending on the compound tested. Generally, CbE was more sensitive to inhibition than AChE when organisms where exposed to OPs, and the opposite trend was observed under carbofuran exposure. Significant inhibition of both enzymatic activities was observed 2 and 6 hours after exposure to carbamate and OPs; while the complete recovery occurred 12- and 96-hours after cessation of carbofuran and OPs exposure, respectively. When CbEs where inhibited (up to 75%) by using specific inhibitors, the toxicity of OPs and carbofuran increased up to 2- and 4-fold, respectively. Thus, CbEs are effective alternative targets for OPs and carbamates in Daphnia, and they play a key role on detoxication. The survival of Daphnia juveniles was impaired at 30 and 80% depression of AChE under carbofuran and OPs exposure, respectively. Hence, depressions of AChE in this range lead to mortality, and can be considered of environmental concern. Key words: carboxilesterase, acetylcholinesterase, daphnia magna, Biomarker |
