Effect of dental materials on gluconeogenesis in rat kidney tubules

The effect of dental composite components triethyleneglycoldimethacrylate ( TEGDMA) and hydroxyethylmethacrylate (HEMA) as well as mercuric chloride (H gCl2) and methylmercury chloride (MeHgCl) on gluconeogenesis was investigat ed in isolated rat kidney tubules. From starved rats kidney tubules were pr epared and isolated by digestion with collagenase. Every 10 min up to 60 mi n l-ml samples were drawn from the cell suspension for quantitating the glu cose content. Glucose formation in controls was 3.3 +/- 0.2 nmol/mg.per min (mean +/- SEM, n = 21). Relative rates of glucose formation were obtained by expressing individual rates as a 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 relati ve rates of 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), < 10 (MeHgCl), and <10% (HgCl2). Values of 50% effective concentration (EC50) were calculated from fitted cu rves. EC50 values were (mmol; mean +/- SEM; n = 4). HEMA, 17.7 +/- 2.9; TEG DMA, 1.8 +/- 0.2; MeHgCl, 0.018 +/- 0.0005; and HgCl2, 0.0016 +/- 0.0005. T he toxic effect of HgCl2 was similar to 1000 or 10 000 higher than that of the dental composite components TEGDMA or HEMA, respectively.