Cell-based bioassays are very sensitive and allow integrative effect screening of the whole environmental sample, which is usually composed of a mixture of agonists and antagonists. Measured toxicity is usually expressed as a bioanalytical equivalent concentration. So far, it is not possible to distinguish which part of this value is caused by the agonists and which by the antagonists. In this article, we present a simple method to analyze the dose-response curve of a mixture and to determine an agonistic bioanalytical equivalent concentration: a concentration of a reference chemical that would elicit the same effect as do only agonists in an unknown mixture. The method has been validated using several artificially prepared mixtures of agonists and competitive antagonists measured in a recombinant yeast assay. No difference was observed between the calculated equivalent concentrations and the used concentrations of the agonist in the mixture.

The Laboratory of Environmental Biotechnology Institute of Microbiology of the Czech Academy of Sciences Vídeňská 1083 Prague 142 20 Czech Republic

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