2007 年 56 巻 4 号 p. 273-278
Germfree mice died when they were fed a purified diet of AIN-76 formula sterilized by γ-irradiation. Vitamin K deficiency was suspected and this study was performed to confirm the cause of the death. Germfree mice were fed purified diets of AIN-76 or AIN-93M formula, which were pelleted and sterilized by γ-irradiation at a dose of 50 kGy. One half of the mice fed the AIN-76 diet died within two weeks and the surviving animals were also in poor health, while 91% of mice fed the AIN-93M diet survived. No hemorrhage was observed grossly in any organs of the surviving animals. Histologically, degeneration with inflammatory cell infiltration was observed as well as hemorrhage and fibrosis in the heart muscles of mice fed the AIN-76 diet. No microscopic lesions were observed in the other organs. Prothrombin time (PT) and activated partial thromboplastin time (APTT) were extremely prolonged when mice were fed the AIN-76 diet. The animals totally recovered when they were intragastrically administered 1 μg/day of vitamin K3 from the third day of feeding of the AIN-76 diet, except for PT and APTT which were still slightly longer than in mice fed the AIN-93M diet. The concentration of vitamin K3 supplied in the AIN-76 diet decreased to an undetectable level after γ-irradiation, while the AIN-93M diet contained 240 μg/kg of vitamin K1. These results indicate that the deaths of the germfree mice fed the γ-irradiated AIN-76 diet were caused by vitamin K deficiency. Vitamin K deficiency may cause fatal degeneration of cardiac muscle cells.