OVEREXPRESSION OF CELLULAR GLUTATHIONE-PEROXIDASE DOES NOT AFFECT EXPRESSION OF PLASMA GLUTATHIONE-PEROXIDASE OR PHOSPHOLIPID HYDROPEROXIDEGLUTATHIONE-PEROXIDASE IN MICE OFFERED DIETS ADEQUATE OR DEFICIENT INSELENIUM

Selenium-dependent cellular glutathione peroxidase (GPX1) overexpressi ng [GPX1(+)] mice were derived by microinjecting a 5.3-kb cloned entir e mouse GPX1 genomic DNA into fertilized eggs. The objective of this s tudy was to determine the effect of GPX1 overexpression and dietary se lenium on the expression of selenoperoxidases and the status of lipid peroxidation of these transgenic animals. An experiment with a 2 x 2 f actorial arrangement of treatments with 15 GPX1(+) and 15 control mice (2 mo old) was conducted for 8 wk. Ten mice of each group (half males and females) were fed a Se-deficient, Torula yeast basal diet (0.02 m g Se/kg, no supplemental vitamin E) and five mice (three males and two females) were fed the basal diet supplemented with 0.51 mg Se/kg as N a2SeO3. The GPX1(+) mice had greater GPX1 activities (one- to sixfold, P < 0.0001) than the control mice at both levels of dietary selenium in all tissues except for liver, in which such difference (100%, P < 0 .05) was observed only in Se-deficient mice. The GPX1 mRNA level in ki dney and in lung of the Se-deficient GPX1(+) mice was 81% and 7.5-fold greater (P < 0.003) than the respective control level. Overexpression of GPX1 did not alter phospholipid hydroperoxide glutathione peroxida se (GPX4) activities and mRNA levels or glutathione S-transferase (GST ) activities in most of the tissues, plasma glutathione peroxidase (GP X3) activity or plasma Se concentrations. No differences in lipid pero xidation in kidney, lung or intestine were observed between the Se-def icient GPX1(1) and control mice. In conclusion, the overexpression of the GPX1 gene in these mice was tissue specific and did not affect the expression of GPX3, GPX4 or GST and plasma Se levels; dietary Se appe ared to affect the GPX1 overexpression at its mRNA level.