Short-term assay for the identification of neurotoxic compounds and their liver derived stable metabolites.

The release of stable neurotoxic metabolites from liver after metabolic activation of xenobiotics can be investigated in cultures of primary rat hepatocytes as metabolic activation system and embryonic chicken brain cell cultures as target. It was shown that adult rat hepatocyte cell cultures are a reliable bioactivating system for xenobiotics such as cyclophosphamide and isophenphos resulting in the release of stable metabolites into the supernatant. The cultured embryonic chicken brain cells were able to discriminate between the toxicity of parent drugs and its metabolite(s) and between metabolites with an unspecific cytotoxic activity (cyclophosphamide) and metabolites with a high potential to damage specific nerve cell population(s) (isophenphos). The observed neurotoxicity of the isophenphos metabolites is not an acute effect but induced only after a prolonged exposure period. The present study provides evidence that the subsequent use of hepatocytes and brain cell cultures has the potential to be used as an in vitro screening system for the identification of specific and non-specific neurotoxic compounds. Solely stable metabolites are taken into account, since in the in vivo situation only stable metabolites have a change to reach the nervous system. Our data suggest that the present approach is able to discriminate (a) between cell-type and organ specific toxicity, (b) between neurotoxicity derived after long-term or acute exposure, and (c) between the neurotoxicity induced by the native test compound or stable metabolites.