[The activity of the peroxide-metabolizing system in human liver (author's transl)].

The activities of various peroxide-metabolizing enzymes were determined in homogenates of human liver excisions. The specific activity of selenium-dependent glutathione peroxidase was 41.1 +/- 23.7 (S.D.) mU/mg protein; non-selenium glutathione peroxidase showed a activity of 30.5 +/- 14.0 mU/mg protein. The catalase and superoxide dismutase concentrations were 4.72 +/- 0.58 and 1.87 +/- 0.68 microgram/mg protein, respectively. Total glutathione amounted to 12.9 +/- 7.4 nmol/mg. Malondialdehyde formation, used as the basis for the determination of lipid hydroperoxides, was 0.32 +/- 0.14 nmol/mg. The data indicate much lower enzyme and substrate levels compared to rats and mice. A positive correlation of r = 0.48 +/- 0.31 was found between the glutathione level and selenium-dependent peroxidase. Selenium-dependent and non-selenium-glutathione peroxidase correlate negatively (r = -0.71 +/- 0.18); superoxide dismutase concentration and lipid-hydroperoxides are also related by a negative correlation coefficient of r = 0.47 +/- 0.31. These data stress the major hepatoprotective role of these systems in human liver.