Hemodialysis may induce hemolysis, thereby heme overload, release of iron and further increase of the peroxidative reactions in the blood of patients. We studied the activity of the rate limiting enzyme of heme degradation, heme oxygenase (HOX) and that of ferroxidase (FOX), together with the level of plasma lipid peroxides (expressed as MDA) in 11 adolescent patients and in 12 aged matched controls.

The blood carboxyhemoglobin and plasma bilirubin levels (Bi) showed positive correlation in the controls (r=0.8769, p<0.01) but not in the patients. HOX activity expressed as Bi/(Bi+plasma hemoglobin) and ferroxidase activity were lower (0.25±0.05 versus 0.31±0.07, p<0.01 and 610±160 mU/ml versus 760±120 mU/ml, p<0.05), while the MDA level was significantly higher (2.25±0.77 μmol/l versus 1.38±0.74 μmol/l, p<0.01) in the patients than in the controls. In the hemodialysis patients, both plasma total ferroxidase and ceruloplasmin activities correlated inversely with the MDA level (r=-0.69, p<0.05 and r=-0.74, p<0.05).

In case of HD induced hemolysis, the low activities of HOX and FOX may contribute to the increased lipid peroxidation observed in the uremic patients.