Cytotoxicity and biotransformation inducing activity of rodent beddings: a global survey using the Hepa-1 assay.

Unknown and uncontrolled toxic materials in the environment of experimental animals endanger the reliability of research results. In this study, the cytotoxic and biotransformation inducer activity of beddings obtained from a number of institutes in Africa, Americas, Asia, Australia and Europe were compared using the Hepa-1 in vitro-assay. A great variation in both cytotoxicity and inducer activity was observed. Pine shavings beddings, commonly used all over the world appeared in general to be highly cytotoxic. Extracts of corn cob, rice hulls and straws, used in a few laboratories, were practically non-toxic. Some softwood extracts, especially from pine, were also potent inducers of cytochrome P4501A1. Grass as well as hardwood materials were much less active. Due to great variation in toxicity and inducer activity in the beddings it is possible that, in spite of standardization of feed and other environmental factors, different biological responses to chemicals and drugs in even genetically identical animal strains in different laboratories, may be obtained. Control of bedding, one of the animals' closest environmental factors, for its toxicity and biotransformation enzyme induction is strongly recommended.