DIETARY SELENIUM REGULATION OF GLUTATHIONE-PEROXIDASE MESSENGER-RNA AND OTHER SELENIUM-DEPENDENT PARAMETERS IN MALE-RATS

Weanling male rats were fed a basal torula yeast diet (0.007 mu g Se/g diet) supplemented with graded levels of Se (0 to 0.2 mu g Se/g diet as Na2SeO3) (three rats/group) to evaluate classical glutathione perox idase (GPX1, GSH:H2O2 oxidoreductase, EC 1.11.1.9) mRNA level as an in dicator of intracellular Se status. Growth was followed throughout the dietary treatment and a number of Se-dependent parameters including l iver GPX1 mRNA levels were determined after 33 days. Growth was not im paired at any level of dietary Se supplementation. In rats fed the Se- deficient basal diet, liver Se concentration was 5 +/- 1%, liver GPX1 mRNA levels were 10 +/- 2%, plasma GPX activity was 2 +/- 1%, erythroc yte GPX activity was 37 +/- 1%, and liver GPX activity was 0 +/- 2% of the levels in rats fed 0.1 mu g Se/g diet; these parameters increased sigmoidally with increasing dietary Se, showing a breakpoint near 0.1 mu g Se/g diet. Graphical analysis indicated that the increase in liv er GPX1 mRNA level with increasing dietary Se, preceded the increase i n liver GPX activity. Se supplementation had no effect on polyadenylat ed mRNA levels or on beta-actin mRNA levels, demonstrating that Se reg ulation of GPX1 mRNA is specific. Se-deficient liver selenoprotein P m RNA levels were 69 +/- 2% of the levels in rats fed 0.1 mu g Se/g diet . We hypothesize that GPX1 mRNA is a primary target of the Se regulato ry mechanism, making GPX1 mRNA level a potentially useful indicator of the status of an important intracellular regulatory pool of Se. (C) E lsevier Science Inc. 1997.