Inclusion of Physicochemical Data in Quantitative Comparisons of <i>In Vitro</i> and <i>In Vivo</i> Toxic Potencies

Abstract

In order to evaluate the relevance of in vitro test systems for acute toxicity assessment, quantitative comparisons of in vitro and in vivo potency data have to be performed. The potency of chemicals to cells in vitro is usually characterised by nominal effective concentrations (e.g. EC50 values). Often, the only available in vivo data are acute lethal body doses (e.g. LD50 values). To enable a reasonable quantitative in vitro–in vivo comparison to be made, a formula has been developed to permit the conversion of EC50 values into “effective model body doses, ED50 values”. This formula takes into account the lipophilicity of the compounds and the very different relationships between the volumes of the lipid and water compartments in vitro and in vivo. The suitability of this approach is evaluated with results obtained for the first 30 MEIC chemicals.