THE RELATIONSHIP BETWEEN HAPTOGLOBIN POLYMORPHISM AND OXIDATIVE STRESS IN HEMODIALYSIS PATIENTS

Background: The relationship between haptoglobin polymorphism and oxidative stress in hemodialysis patients is not fully understood. In this study, total antioxidant capacity and ceruloplasmin ferroxidase activity were evaluated in relation to haptoglobin phenotype distribution in hemodialysis patients. Methods: Serum samples collected from 161 patients and 84 healthy controls were haptoglobin-typed by electrophoresis. Ceruloplasmin ferroxidase activity and total antioxidant capacity were assayed using colorimetric methods. Results: Irrespective of the haptoglobin phenotype, patients exhibited significantly lower total antioxidant capacity (1.42+/-0.29 vs. 1.55+/-0.28 mmol/L, P=0.002) and higher ferroxidase activity than controls. Frequency of Hp1-1 and Hp2-1 in patients was 15.5% and 36% as compared with 9.5% and 41.7% in controls. While ferroxidase activity was lower in Hp2-2 patients than in controls (142+/-61 vs. 179+/-47 U/L, P=0.002), it was higher in Hp2-1 (173+/-56 U/L) and Hp1-1 (170+/-54 U/L) patients than in controls (141+/-43 and 99+/-30 U/L respectively) (P=0.002 and 0.009). Ferroxidase activity in Hp2-2 patients was significantly lower than that of Hp2-1 or Hp1-1 patients (P=0.004 and 0.034). Total antioxidant capacity was significantly lower only in Hp2-2 patients (1.44+/-0.25) compared to that in Hp2-2 controls (1.65+/-0.22) (P=0.000). Conclusions: These findings suggest that haptoglobin polymorphism can differentially impact oxidative stress levels in hemodialysis patients.