A decrease of intracellular ATP is compensated by increased respiration and acidification at sub-lethal parathion concentrations in murine embryonic neuronal cells: measurements in metabolic cell-culture chips.

We present a label-free in vitro method for testing the toxic potentials of chemical substances using primary neuronal cells. The cells were prepared from 16-day-old NMRI mouse embryos and cultured on silicon chips (www.bionas.de) under the influence of different parathion concentrations with sensors for respiration (Clark-type oxygen electrodes), acidification ( pH-ISFETs) and cell adhesion (interdigitated electrode structures, IDES). After 12 days in vitro, the sensor readouts were simultaneously recorded for 350 min in the presence of parathion applying a serial 1:3 dilution. The parathion-dependent data was fitted by logistic functions. IC50 values of approximately 105 mu M, 65 mu M and 54 mu M were found for respiration, acidification, and adhesion, respectively. An IC50 value of approximately 36 mu M was determined from the intracellular ATP-levels of cells, which were detected by an ATP-luminescence assay using microwell plates. While the intracellular ATP level and cell adhesion showed no deviation from a simple logistic decay, increases of approximately 29% in the respiration and 15% in the acidification rates above the control values were found at low parathion concentrations, indicating hormesis. These increases could be fitted by a modified logistic function. We believe that the label-free, continuous, multi-parametric monitoring of cell-metabolic processes may have applications in systems-biology and biomedical research, as well as in environmental monitoring. The parallel characterization of IC50 values and hormetic effects may provide new insights into the metabolic mechanisms of toxic challenges to the cell. (C) 2011 Elsevier Ireland Ltd. All rights reserved.