抄録
When injected with pyrithiamine in amounts larger than 0.2 mg per gram of body weight in a single dose, mice fed even on a ordinary diet showed symptoms similar to the thiamine deficiency. The lethal doses of pyrithiamine for the above animals and mice fed on a thiamine deficient diet for a fortnight were 0.5 mg/g and 0.3-0.35 mg/g respectively. Based on the assay of thiamine in the whole homogenate of the above animals, it was roughly estimated that the ratio of the amount of combined thiamine in the animals bodies to the lethal doses of injected pyrithiamine was 1 : 220-230 in both cases. In mice on a thiamine deficient diet for a fortnight 0.035 mg/g of thiamine competed with 0.35 mg/g of pyrithiamine elongating their lives by 7-11 days, and 0.11 mg of 2-ethyl-thiamine which has an ethyl group instead of methyl at 2-position of the pyrimidine moiety of thiamine, could prolong them by 5-8 days in competition with pyrithiamine. The single administration of the same dose of ethylthiamine made the lives of the thiamine deficient mice 8-14 days longer. From these facts it was concluded that 2-ethylthiamine had really a thiamine activity though it was weaker than that of the ordinary thiamine.
