Thiamin metabolism in the rat during long term alcohol administration.

In order to test the effect of a long term alcohol administration on the thiamin metabolism in blood, heart and liver under suboptimal supply, an experiment with rats was carried out over a period of 16 weeks. The suboptimal thiamin supply became visible mainly in the liver stores which were lowered during the whole test period. The unphosphorylated thiamin (T) of liver and heart was not detectable after 4 weeks up to the end of experiment. On the other hand the total thiamin concentration in the erythrocytes increased from the beginning due to an enhanced thiamin-diphosphate (TDP) and thiamintriphosphate (TTP) pool and T was lowered to undetectable amounts only after 16 weeks. In contrast, the alpha-TK in blood and liver was enhanced only after 2 and 4 weeks and tended to become normal by the end of the test period indicating an apoenzyme degeneration. Alcohol ingestion resulted in a general diminution of the total thiamin and the thiamin phosphates in blood, heart and liver and a reduced thiamin excretion in urine. An alcohol induced shift of the phosphorylation status could be observed only in the liver, but not in the heart and the erythrocytes, leading to a lowered concentration of T and TMP. The results demonstrate that the level of thiamin and thiamin phosphates in blood and organs under suboptimal thiamin supply seems to be more sensitive to chronic alcohol administration than the transketolase activity and the alpha-TK value.