Thiamine metabolism in the liver of mice with Ehrlich ascites carcinoma

Thiamine pyrophosphate (TPP) content, activities of thiamine pyrophosphokinase (TPKase), thiamine pyrophosphatase, transketolase (TK), pyruvate (PDG) and oxoglutarate dehydrogenases (OGDG) were measured in the liver and cells of Ehrlich ascites carcinoma (EAC) on the 5th, 10th and 15th day after transplantation of the tumor to mice fed a thiamine-deficient diet. The TPP level gradually decreased in the liver of tumor-bearing mice but remained constant in tumor cells (1.06 +/- 0.02 microgram/g tissue). Deprivation of dietary thiamine lowered the liver TPP level even to a greater extent, and subsequent daily 10 micrograms thiamine/mouse injections did not restore it. The TPKase activity in the liver of mice with EAC decreased by 24% and in thiamine deficiency, by 44%. The liver PDG, OGDG and TK activities were reduced but slightly in mice with EAC, whereas thiamine deprivation resulted in a decrease of the enzyme activities: PDG by 60%, OGDG by 25% and TK by 45%. TK activity in tumor cells was 90 mumol S-7-P/g tissue/h, and the TPP effect amounted to 24%. Thiamine deprivation decreased the TK activity by 45% and raised the TPP effect up to 180%. Thiamine injections restored the TK activity in tumor cells and reduced the TPP effect.