Uptake of pyrithiamine (
PyT
) by tissues of normal and thiamine-deficient rats was compared.
1.
PyT
concentration in livers of both normal and thiamine deficient rats reached a maximal level of approximately 20μg/g within 1 hour after the intraperitoneal injection of 10mg/kg of
PyT
, and then decreased. The rate of decrease of
PyT
was much slower in the deficient liver than in the normal one. The former retained about 8μg/g of
PyT
even after 6 days, while the latter retained less than 0.5μg/g.
2. Brain and muscular tissues took up
PyT
very slowly, and the maximal concentrations were obtained 24 to 48 hr after the injection.
PyT
levels in these tissues of the deficient rats were markedly higher and maintained for a longer time than that of normal ones.
3. The thiamine levels in tissues of
PyT
treated normal rats decreased temporarily in accordance with the time of
PyT
accumulation. In thiamine-deficient tissues except brain, thiamine levels decreased to a very low level and were not further affected by
PyT
administration. The brain thiamine level decreased by the injection of
PyT
.
4. The increased
PyT
levels of
PyT
treated thiamine-deficient rats were quickly decreased by the administration of thiamine.
5. Most of the
PyT
taken up by the tissues of thiamine-deficient rats was present as the phosphorylated form.
6. When an equimolar amount of
PyT
or thiamine was administered to thiamine-deficient rats, more
PyT
was taken up by the tissues than thiamine. Coadministration of
PyT
and thiamine caused reduction of the uptake of both compounds.
7. The mechanism of the thiamine lowering action of
PyT
was discussed.
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