ROLE OF BILIRUBIN IN THE REGULATION OF THE TOTAL PEROXYL RADICAL TRAPPING ANTIOXIDANT ACTIVITY OF PLASMA IN SICKLE-CELL DISEASE

Alpha-tocopherol and bilirubin antioxidant properties were evaluated i n sickle cell disease. The total peroxyl radical trapping antioxidant activity of plasma (TRAP) was measured with a polarographic method usi ng hemin as oxidative stress initiator. The TRAP was not correlated wi th plasma alpha-tocopherol concentration. The TRAP was correlated with plasma total bilirubin concentration [TRAP = 8.1 (total bilirubin) +3 63.7 (r = 0.67)] and the correlation was even better with the sum (alp ha-tocopherol + total bilirubin) plasma concentration [TRAP = 9.1 (alp ha-tocopherol + total bilirubin)+ 170.5 (r = 0.77)]. The alpha-tocophe rol contribution in the antioxidant capacity of plasma was significant but bilirubin level acted as the limiting factor of plasma antioxidan t capacity in sickle cell anemia. This result can be explained by the antioxidant property of bilirubin but also by coantioxidant activity t owards oxidized alpha-tocopherol, (C) 1998 Academic Press.