Uranium toxicity on plant cells: Isothermal microcalorimetric studies for the differentiation between chemotoxic and radiotoxic effects of uranium


Uranium toxicity on plant cells: Isothermal microcalorimetric studies for the differentiation between chemotoxic and radiotoxic effects of uranium

Sachs, S.; Oertel, J.; Fahmy, K.

The transfer of radionuclides into the food chain is a central concern in the safety assessment of both nuclear waste repositories and remediation strategies in radioactively contaminated sites, such as legacies of the former uranium mining. The uptake and translocation of radionuclides, e.g., uranium, is speciation dependent and induces several stress response reactions, which changes the plant metabolism. Correlating molecular information on radionuclide speciation and biomolecular interactions with physiological performance is a major challenge for radioecology.
In our previous work we applied isothermal microcalorimetry as a sensitive real-time monitor to study the interaction of U(VI) with canola (Brassica napus) cells (Sachs et al., 2017). Applying this method we were able to monitor the metabolic activity of the cells in the presence of U(VI) and to determine the U(VI) toxicity in B. napus cells. Those was correlated with the oxidoreductase activity of the cells and the U(VI) speciation in solution. Based on this work we are currently investigating the differentiation between chemotoxic and radiotoxic effects of uranium on B. napus cells applying natural uranium as well as 233U as alpha emitter. To discriminate between these effects, the metabolic heat flow of the cells at a constant total uranium concentration of 50 µmol/L is monitored by isothermal microcalorimetry applying increasing concentrations of 233U (1-15 µmol/L), which correspond to increasing radiation doses. Applying liquid scintillation counting (LSC) we determine the amount of uranium that is bioassociated to the plant cells and estimate the respective 233U doses for the cells.
Mc values provide a quantitative ranking of metabolic activities that is independent of cell number and largely unaffected by normal variations between experiments (Sachs et al., 2017). Our data are normalized to Mc values of B. napus cells that were exposed to natural uranium only. In the presence of 2 µM 233U a slight increase in the Mc values was observed, which indicates a slightly higher metabolic activity of the cells. Probably, this is an indication for a stress response of the cells to the radiotoxic effect of 233U. With increasing 233U concentration only a slight decrease of the Mc values was observed. This indicates only a slight effect of the alpha radiation on the cells compared to those cells that were exposed to natural uranium, which exhibits a predominant chemotoxic effect. These first results point to a high resistance of B. napus cells to the radiotoxicity of 233U.
This presentation will demonstrate the potential of life cell microcalorimetry for radioecological studies. We will present the calorimetric determination of the U(VI) toxicity in B. napus cells that correlates with oxidoreductase activity and U(VI) speciation and will focus on the differentiation between chemotoxic and radiotoxic effects of uranium.

Sachs, S., Geipel, G., Bok, F., Oertel, J., Fahmy, K. 2017. Calorimetrically determined U(VI) toxicity in Brassica napus correlates with oxidoreductase activity and U(VI) speciation. Environ. Sci. Technol. 51, 10843-10849.

Keywords: uranium; plant cells; toxicity; isothermal microcalorimetry

  • Lecture (Conference)
    ENVIRA 2019, 5th International Conference on Environmental Radioactivity, 08.-13.09.2019, Prague, Czech Republic

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Publ.-Id: 29272