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2D - Mechanisms of toxic action (MOP/97) Toxic Effects and Mechanisms of Toxicity of Reactive Chemicals in Green Algae. Niederer, Christian1, 2, Escher, Beate1, 1 EAWAG Swiss Federal Institute for Environ. Sci. and Technol., Duebendorf, Switzerland2 ETH Swiss Federal Institute of Technology, Zuerich, Switzerland ABSTRACT- Effect assessment of reactive electrophilic chemicals in algae is limited by the fast hydrolysis of these compounds, which renders them unsuitable for 72h growth inhibition tests. It was therefore the goal of this study to establish and evaluate toxicity indicators for reactive chemicals in the green algae Scenedesmus vacuolatus after short term exposure of two hours. Methods evaluated include growth recovery experiments and chlorophyll fluorescence quenching. The enhanced toxicity of reactive chemicals is caused by unselective alkylation of essential cellular biomolecules such as DNA, proteins, and peptides. Since organisms are well equipped to defeat DNA-damage by various repair systems, genotoxicity is established only under chronic exposure or at high concentrations in acute tests. Other cellular components, namely certain proteins and peptides, react faster to alkylating chemicals resulting in acute disturbance of cellular processes. Therefore interference with glutathione metabolism, in particular glutathione induction and depletion were also investigated. The methods were evaluated with the reactive chemicals epichlorohydrin, styrene-7,8-oxide, trans-1,4-dichloro-2-butene, 1,2-epoxybutane, (2,3-epoxypropyl)benzene, and benzylchloride. With the established test battery it is possible to draw not only reliable conclusions about the acute toxicity of reactive chemicals but also obtain information on the mechanisms of toxic action. Key words: chlorophyll fluorescence, Scenedesmus vacuolatus , glutathion depletion, algae |
