The effect of progressive selenium deficiency on anti-glutathione peroxidase antibody reactive protein in rat liver.

Liver glutathione peroxidase (GSH-Px, EC 1.11.1.9) activity decreases when weanling rats are fed a Se-deficient diet. To determine the effect of dietary Se deficiency on the concentration of the protein portion of GSH-Px, weanling rats were fed a Se-deficient (less than 0.02 ppm Se) or a Se-supplemented (0.2 ppm Se as Na2SeO3) 30% torula yeast-based diet and killed 0, 3, 7, 14, 21 or 28 d later. GSH-Px activity was assayed using H2O2, so only the Se-dependent GSH-Px was measured. Anti-GSH-Px antibodies, produced in a rabbit by three injections of purified rat liver GSH-Px, were used in an enzyme-linked immunosorbent assay for GSH-Px protein. Immunoblotting showed that the antibodies were highly specific for GSH-Px. In Se-supplemented rats, liver GSH-Px activity increased 66% and GSH-Px protein increased 50% over the 28 d. In Se-deficient rats, liver GSH-Px activity decreased exponentially to zero with a half-life of 2.8 d. Liver GSH-Px protein also decreased exponentially, but with a longer half-life of 5.2 d (P less than 0.001), and the anti-GSH-Px antibody-reactive protein did not decrease to zero. This experiment shows that both GSH-Px activity and GSH-Px protein decrease exponentially during progressive dietary Se deficiency. The longer half-life of GSH-Px protein compared with GSH-Px activity suggests that an inactive GSH-Px polypeptide is present in rat liver during the early stages of Se deficiency.