Synergistic effects of H2O2 with components of dental restorative materials on gluconeogenesis in rat kidney tubules

No data are available about (toxic) effects of dental materials administered in combination with H2O2 from dental bleaching compounds. The effect of dental composite components triethyleneglycoldimethacrylate (TEGDMA) and hydroxyethylmethacrylate (HEMA) as well as mercuric chloride (HgCl2) and methylmercury chloride (MeHgCl), each in combination with H2O2, was investigated on gluconeogenesis in kidney cells. From rats kidney tubules were prepared. Every 10 min up to 60 min 1-ml samples were drawn from the cell suspension for quantitating the glucose content. Glucose formation in controls was 3.5±0.3 nmol/mg•per min (mean±SEM, n=21). Relative rates of glucose formation were obtained by expressing individual rates as percentage of the corresponding control. X–Y concentration curves (effective concentration, EC) of the substances were calculated by fitting a four-parametric sigmoid function to the relative rates of the glucose formation at various test concentrations. At the end of the incubation period cell viability was assessed by trypan blue exclusion. Cell viability decreased within the 60 min interval from 90% to approx. 80% (controls), <25 (HEMA), <20 (TEGDMA), <20 (H2O2) <10 (MeHgCl), and <10 (HgCl2). Values of 50% effective concentration (EC50) were calculated from fitted curves. EC50 values were (mmol/l; mean±SEM; n=4): HEMA, 17.2±2.8; TEGDMA, 1.9±0.2; H2O2 0.22±0.03, MeHgCl, 0.016±0.0005; and HgCl2, 0.0017±0.0005. No significant decrease of the EC50 values was found when kidney cells were exposed to HEMA, HgCl2, or MeHgCl in addition with H2O2 (1–100 μ ), compared to those EC50 values of each compound without H2O2 addition. A significant decrease of the TEGDMA EC50 values to about 0.25 or 0.04 (mmol/l) was found when cells were exposed to TEGDMA in combination with H2O2 (75 or 100 μ ), compared to that TEGDMA EC50 value without H2O2 addition. The addition of H2O2 (75 and 100 μ ) resulted in a synergistic toxic effect of TEGDMA