Fig. 3.

Cu decreases selenoprotein activity, but does not directly affect enzyme activity within the assay. HepG2 cells were cultured with increasing Cu concentrations (0, 25, 50 or 100 μM) in combination with or without 50 nM selenite for 72 h (A, C). Lysates of selenite supplemented (50 nM for 72 h) cells were used to measure the direct impact of Cu on enzyme activities (B, D). Increasing concentrations of Cu were added 15 min prior to measurement of enzyme activities and were normalized to lysates without additional Cu. Activities of GPX (A, B) and TXNRD (C, D) were measured photometrically and normalized to protein content. Data are depicted as mean + SD (n = 3-4). Statistical analyses were based on two-way ANOVA with Bonferroni's post-test (A, C) or one-way ANOVA (B, D) with Bonferroni's post-test. *p < 0.05; **p < 0.01; ***p < 0.001 vs. 0 nM CuSO₄ and ^#p < 0.05; ^##p < 0.01; ^###p < 0.001 vs. 0 nM Se.