Role of NADH-cytochrome b(5) reductase in biosynthesis of thyroid hydrogen peroxide / 生理学报

ABSTRACT

The activity of NADH-cytochrome b(5) reductase (b(5)R) and the levels of hydrogen peroxide in the thyroid of patients with Graves' disease (GD) and normal controls were measured with potassium ferricyanide as substrate and with the homovanillic acid fluorescence assay. The activity of b(5)R and the level of H2O2 in GD thyroid were definitely higher than those in normal control, but the activity of catalase in GD thyroid was not significantly different from that in normal thyroid. After addition of p-chloromercuribenzoate, a b(5)R inhibitor, the activity of b(5)R in GD and normal thyroid decreased by 85%, the level of H2O2 decreased by 50%, and protein-bound iodine (PBI) formation by 52%. There is a positive correlation between the level of H2O2 and the activity of b(5)R. Our data indicate that b(5)R participates in thyroid hydrogen peroxide biosynthesis, and is an important enzyme in the production of H2O2.