In Vitro Assessment of Modes of Toxic Action of Pharmaceuticals in Aquatic Life

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• 作者：Beate I. Escher ; Nadine Bramaz ; Rik I. L. Eggen ; and Manuela Richter
• 刊名：Environmental Science & Technology
• 出版年：2005
• 出版时间：May 1, 2005
• 年：2005
• 卷：39
• 期：9
• 页码：3090 - 3100
• 全文大小：207K
• 年卷期：v.39,no.9(May 1, 2005)
• ISSN：1520-5851

文摘

An ecotoxicological test battery based on a mode-of-action approach was designed and applied to the hazardidentification and classification of modes of action ofsix pharmaceuticals (carbamazepine, diclofenac, ethinylestradiol, ibuprofen, propranolol, and sulfamethoxazole). Therationale behind the design of the battery was to coverthe relevant interactions that a compound may have withbiological targets. It is thus not comprehensive butcontains representative examples of each category ofmode of toxic action including nonspecific, specific, andreactive toxicity. The test battery consists of one test systemfor nonspecific toxicity (baseline toxicity or narcosis),two test systems for specific effects, and two test systemsfor reactive toxicity. The baseline toxicity was quantifiedwith the Kinspec test, which detects membrane leakage viameasurements of membrane potential. This test systemmay also be used to detect the specific effects on energytransduction, although this was not relevant to anycompound investigated in this study. As examples ofspecific receptor-mediated toxicity, we chose the yeastestrogen screen (YES) as a specific test for estrogenicity,and the inhibition of chlorophyll fluorescence in algaeto assess specific effects on photosynthesis. Reactivemodes of action were assessed indirectly by measuringthe relevance of cellular defense systems. Differences ingrowth inhibition curves between a mutant of Escherichiacoli that could not synthesize glutathione and its parentstrain indicate the relevance of conjugation with glutathioneas a defense mechanism, which is an indirect indicatorof protein damage. DNA damage was assessed by comparingthe growth inhibition in a strain that lacks various DNArepair systems with that in its competent parent strain. Mostcompounds acted merely as baseline toxicants in all testsystems. As expected, ethinylestradiol was the only compoundshowing estrogenic activity. Propranolol was baseline-toxic in all test systems except for the photosynthesis inhibitionassay, where it surprisingly showed a 100-fold excesstoxicity over the predicted baseline effect. The exact modeof toxic action could not be confirmed, but additionalchlorophyll fluorescence induction experiments excludedthe possibility of direct interference with photosynthesisthrough photosystem II inhibition. Mixture experiments wereperformed as a diagnostic tool to analyze the mode oftoxic action. Compounds with the same mode of toxic actionshowed the expected concentration addition. In thephotosynthesis inhibition assay, agreement betweenexperimental results and prediction was best for two-stage predictions considering the assigned modes of action.In a two-stage prediction, concentration addition wasused as a model to predict the mixture effect of the baselinetoxicants followed by their independent action as asingle component combined with the specifically actingcompound propranolol and the reference compound diuron.A comparison with acute toxicity data for algae, daphnia,and fish showed generally good agreement for thenonspecifically acting compounds but also that the proposedtest battery offered better diagnostic value in the caseof the specifically acting compounds.