Background: Oxidative stress is a complicating factor in chronic renal failure, especially in hemodialysis (HD) patients. Also, aluminum intoxication may occur during hemodialysis treatment. Aluminum has been shown to inhibit the sulfhydryl-containing enzyme delta-aminolevulinate dehydratase (ALA-D). Thus, the involvement of -SH oxidation in ALA-D inhibition and its relationship with serum Al levels and lipid peroxidation in HD patients were evaluated.
Methods: Blood ALA-D activity, plasma thiobarbituric acid reactive substances (TBARS), and serum aluminum levels were measured in HD patients (n=37) and healthy controls (n=20).
Results: TBARS and Al levels were higher in HD patients than in controls (p<0.01), while ALA-D activity was lower (p<0.05). The sulfhydryl-reducing agent dithiothreitol (DTT) reactivated ALA-D of HD patients, but activity was still lower than that of controls. ALA-D activity was negatively correlated with TBARS (r=-0.63, p<0.01) and aluminum levels (r=-0.31, p<0.05).
Conclusions: Reduced ALA-D activity in HD patients was found to be related to the oxidation of -SH groups essential for enzyme activity. Our results suggest that increased oxidative stress may have contributed to enzyme inhibition in HD patients.