Figure 2. The effects of ascorbate and iron on hydrogen peroxide production in cell culture medium and human plasma.

(a) Concentration of ascorbyl radical (marker of H₂O₂ production) in cell culture medium samples that were collected after incubation of LNCaP or PC-3 cells for the purposes of viability measurements (results presented in Fig. 1); Box: Characteristic EPR signal of ascorbyl radical with spectral simulation (pale); * - statistically significant (p < 0.05) compared to control (no Fe supplemeted). (b) The concentration of molecular oxygen and the rate of O₂ consumption in cell culture medium supplemented with Asc (5 mM) or Fe (5 μM) + Asc (5 mM). CAT (600 U) was added at 15 min. The change in O₂ concentration following CAT supplementation is presented as mean ± S.D. (c) Concentration of ascorbyl radical in human plasma samples collected after the incubation of LNCaP or PC-3 cells for the purposes of viability measurements; A low level of ascorbyl radical was found in some untreated plasma samples; Bars not sharing a common letter are significantly different (p < 0.05). (d) The concentration of molecular oxygen and the rate of O₂ consumption in plasma supplemented with Asc (5 mM). Characteristic polarographic recordings obtained on plasma samples from three healthy volunteers (total Fe concentrations: volunteer (1) 23.0 μM; (2) 15.4 μM; (3) 24.2 μM) are presented. CAT was added at 15 min. Statistical analysis was performed using one-way ANOVA with post hoc Duncan test.