title: Turnover of [14C]thiamin and activities of thiamin pyrophosphate-dependent enzymes in tissues of mice with Ehrlich ascites carcinoma.
abstract: Turnover of [14C]thiamin was studied in mice with Ehrlich ascites carcinoma fed a thiamin-deficient diet and injected with 5 or 2 micrograms/mouse of the labeled vitamin. The process of conversion of [14C]thiamin to thiamin pyrophosphate (TPP) was monitored by measuring the activities of transketolase, pyruvate dehydrogenase, and oxoglutarate dehydrogenase. The amount of coenzyme-unsaturated apotransketolase was assessed by measuring the TPP effect--determining transketolase activity with and without the addition of TPP in vitro. Tumor growth was accompanied by thiamin deficiency, manifested in an increase in [14C]thiamin incorporation into the host tissues and the absence of saturation of the tissues with the labeled vitamin over 13 days. Increased values for the turnover coefficients, reduction of thiamin-dependent enzyme activities, elevation of the TPP effect, and a decrease in urinary excretion of the radioactive products also provided evidence for a disturbance in thiamin metabolism. The severity of the disturbance in thiamin metabolism during malignant tumor growth was directly related to the dose of the exogenous vitamin.
mesh_terms: D000818:Animals; D002250:Carbon Radioisotopes; D002286:Carcinoma, Ehrlich Tumor / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D005260:Female; D007700:Kinetics; D051379:Mice; D013831:Thiamine / Q000378:metabolism*; D013832:Thiamine Deficiency / Q000378:metabolism; D013835:Thiamine Pyrophosphate / Q000378:metabolism*; D014018:Tissue Distribution; D014815:Vitamins
chemical_list: D002250:Carbon Radioisotopes; D014815:Vitamins; D013835:Thiamine Pyrophosphate; D013831:Thiamine