EFFECTS OF ACUTE AND CHRONIC ETHANOL ADMINISTRATION ON THIAMINE METABOLIZING ENZYMES IN SOME BRAIN-AREAS AND IN OTHER ORGANS OF THE RAT

The effect of ethanol (4.7 g/kg body wt intragastrically as a single dose or once daily for 35 days) on the levels of the thiamine metabolizing enzymes (thiamine pyrophosphokinase, TPKase; thiamine pyrophosphatase, TPPase; and monophosphatase, TMPase) was studied in different organs (liver, kidney, small intestine, heart and skeletal muscle) and nervous regions (cerebral cortex, cerebellum, medulla oblongata, pons, corpus callosum, hypothalamus and sciatic nerve) of the rat. In order to evaluate the non-specific effects of the stress of gastric gavage and of the additional caloric intake, appropriate control groups of animals were treated intragastrically with water or with a saccharose solution isoenergetic with ethanol respectively. All animals were reared on a nutritionally adequate diet supplying amounts of thiamine higher than the reccommended daily requirement. Enzymatic activities were determined quantitatively by biochemical methods. Tissue TPKase levels were generally reduced by both acute and chronic ethanol administration. TPPase levels were generally reduced after acute and increased after chronic ethanol treatment. Changes in brain TMPase levels were similar to those observed for TPPase. In visceral organs and skeletal muscle TMPase activity was increased by chronic ethanol treatment as compared to acute ethanol administration. In conclusion, ethanol exerts a marked influence on the tissue levels of the thiamine metabolizing enzymes: the activity of the enzymes dephosphorylating thiamine phosphates is increased whereas the activity of the thiamine pyrophosphate synthesizing enzyme is reduced. These changes may contribute to an important extent to the disturbances in thaimine cellular uptake and metabolism observed in alcoholism.