Qualitative and quantitative modelling of toxic effects of organophosphorous compounds to fish

In this paper a QSAR analysis is applied with the intention of analyzing toxicity data of 20 organophosphorous compounds in terms of possible rate-limiting steps. Several aspects will be discussed and related to the physico-chemical properties of the test compounds. These are: bioconcentration factors, inhibition of acetylcholinesterase (AChE) and biotransformation in oxidative and glutathione-mediated in vitro systems. As expected, relatively simple relationships between toxicity data and K ow, as obtained for narcotic chemicals, were not obtained. The results of this study show that large differences can occur in the toxicity of the chemicals to fish, despite the fact that in vitro parameters for AChE inhibition and biotransformation are approximately equal. From these observations it is concluded that the application of general QSAR models for the estimation of toxicity data of reactive compounds that can be metabolized in vivo is as yet restricted due to our lack of knowledge of specific enzyme activities and of the role of possible extrahepatic biotransformation processes.