Enhancement of glutathione-dependent haemin degradation by ascorbic acid

In the current work, we investigated the effect of ascorbic acid on GSH-mediated haemin degradation. GSH-mediated haemin degradation in the presence of ascorbic acid in phosphate-buffered saline and in erythrocyte ghosts was determined by recording absorbance at 365 and 399 nm, respectively. Generation of intracellular H2O2 was measured indirectly in terms of the inactivation of endogenous catalase in erythrocytes in the presence of 3-amino-1,2,4-triazole. Although ascorbic acid itself did not induce haemin degradation, it enhanced GSH-mediated haemin degradation. Experiments with catalase showed that H2O2 was essential in this process. The oxidation of ascorbic acid in the presence of haemin was stimulated by GSH, suggesting that ascorbic acid can alter the mechanism of H2O2 generation observed with GSH and haemin alone. These results suggest that enhancement of GSH-mediated haemin degradation by ascorbic acid may be due to an increase in the production of H2O2 generated by GSH and haemin in the absence of ascorbic acid. Crown Copyright (C) 2002 Published by Elsevier Science Inc. All rights reserved.