Low levels of dehydroascorbic acid in uraemic serum and the partial correction of dehydroascorbic acid deficiency by haemodialysis

Background. Vitamin C is currently considered a potent water-soluble antioxidant and it appeared reasonable to study the metabolic changes of vitamin C in uraemia and during haemodialysis. Methods. We measured the levels of ascorbic. dehydroascorbic and diketogulonic acids in sera of uraemic patients before and during haemodialysis, using the 2,4-dinitrophenylhydrazine method. Results. The results indicate that the levels of ascorbic and dehydroascorbic acids in uraemic sera are low in comparison with controls, but the levels of diketogulonic acid are higher than in healthy persons. The comparison of ratios between levels of these substances in uraemic sera and in normal sera indicate that the oxidation of ascorbic acid to dehydroascorbic in uraemia proceeds much slower than in controls. We propose that uraemic patients are characterized by pronounced deficiency of dehydroascorbic acid. A marked decrease of ascorbic and diketogulonic acid plasma levels, and a pronounced increase of dehydroascorbic acid levels during haemodialysis was observed. Ratios between plasma levels of ascorbic and dehydroascorbic acids following haemodialysis are the same as in healthy persons. Conclusion. Uraemic patients are characterized by marked deficiency of dehydroascorbic acid and this deficiency can be partially corrected by haemodialysis.