Human erythrocytes are protected against chromate-induced peroxidation

In previous studies performed in this laboratory it was realized that in a broad concentration range (0.5-8 mM) dichromate does not induced red blood cell (RBC) peroxidation, To investigate the reasons behind RBC protection a gainst chromate-induced peroxidation, the effects of 8 mM dichromate on whi te ghost and RBC peroxidation, RBC antioxidant system and hemoglobin status , as well as RBC osmotic fragility and morphology, were studied in more det ail. It was observed that the peroxidation level induced by dichromate on R BCs is practically negligible when compared with the peroxidation induced i n white ghosts. Furthermore, the osmotic fragility of RBCs exposed to dichr omate is not altered, but the cells undergo echinocytic transformation, pro bably due to chromate-induced structural RBC membrane modifications. The ac tivities of catalase, gluthatione peroxidase, and superoxide dismutase of R BCs exposed to dichromate were similar to those observed in controls, but t he gluthatione reductase and GSH levels were significantly reduced (P < 0.0 5), Concomitantly, GSSG and methemoglobin levels increased and NADH-methemo globin reductase activity decreased. These results indicate that chromate d oes not induce RBC peroxidation, but does promote echinocytic shape transfo rmation, oxidation of hemoglobin and GSH, and inhibition of gluthatione red uctase and methemoglobin reductase, The enzymatic antioxidant defense syste m and hemoglobin oxidation are probably involved in the mechanism of RBC pr otection against chromate-induced peroxidation, as is discussed. (C) 1999 A cademic Press.