FIG. 3.

Incubating either L cells or NIH 3T3 cells in Se-deficient medium for 24, 48, or 72 h decreases Se-GPx1 activity to 50 to 55% of the activity of Se-supplemented cells. Activity was measured according to the method of Paglia and Valentine (36), as modified by Reddy et al. (39). Each cell line was mock transfected with either DEAE dextran (L cells) or calcium phosphate (NIH 3T3 cells) and incubated for an additional 12 h before the medium was changed to either Se-deficient (−) or Se-supplemented (+) medium. Se-GPx1 activities are presented as the means of duplicate measurements for each time point.