Influence of body weight of mice on the susceptibility to okadaic acid, a diarrhetic shellfish poisoning toxin

The mouse bioassay (MBA) for diarrhetic shellfish poisoning (DSP) toxins has been widely used in many countries of the world. However, different body weight ranges of mice are designated to be used in the Japanese official method and European Union procedure. In this study we investigated whether and to what extent the body weights of the mice affect the susceptibility to DSP toxins. A lethal dose of okadaic acid, one of the representative DSP toxins, was injected intraperitoneally into mice of five different body weight range groups, from 14 to 24 g. The mice were observed until 24 h after injection. The lethality was 100% in the 14–15 and 16–17 g groups, 80% in the 19–20 g group, 50% in the 21–22 g group, and 40% in the 23–24 g group, with significant differences. Survival analysis indicated a relationship between body weights of mice and susceptibility to okadaic acid. These results would be quite useful not only for the MBA, but also to improve understanding of the biological responses to DSP toxins.