Evaluation of the physiology of Medaka as a model animal for standardized toxicity tests of chemicals by using mRNA expression profiling.

The fish acute toxicity test in the Organisation for Economic CoOperation and Development "OECD Guidelines for Testing of Chemicals" is an essential test for environmental toxicity. Here, we have tried to evaluate the physiology of medaka during these test procedures by using genomics. Genomics technology can provide genome-wide expression profiles of mRNA, and these profiles correspond to the physiology of organisms. Thus, a comparison of mRNA expression profiles gives information on the reproducibility of experimental conditions. Expression profiles of mRNA were measured for medakas maintained within the allowable range of the test conditions and also under extreme conditions beyond the guideline limits. We confirmed the high physiological reproducibility of medaka kept in the recommended conditions of the fish acute toxicity test in the "OECD Guidelines for Testing of Chemicals" from the expression profiles obtained under all experimental conditions, except for the types of feeding.