title: Neuronal in vitro activity is more sensitive to valproate than intracellular ATP: Considerations on conversion problems of IC50 in vitro data for animal replacement.
abstract: We investigated the effects of acute valproate (VPA) on mouse embryonic primary cortex cells (MEPCs). Intracellular ATP concentrations were compared with changes in the mean action potential (AP) frequencies of MEPC networks growing on microelectrode arrays. Our data implies biphasic reactions towards increasing VPA concentrations for both parameters. Intracellular ATP and mean AP frequencies increased around characteristic concentrations of 0.15 and 0.07mM to hormetic plateaus of approx. 120% and 160% of their controls, before fading around 17 and 1.7 mM, respectively. The biphasic in vitro behavior of the two parameters hinders a simple extraction of IC50 and Hillslope values. Different ways of data-fitting with single and double logistic functions are discussed. For a typical hormetic increase of 60% above control, IC50 and Hillslope were decreased by 37% and 15%, respectively. Despite these marginal effects at a logarithmic concentration scale, the hormetic and double logistic behavior of parameters may provide information on the mode of action of toxic compounds. Comparison of our values with the LD50 of mice, recalculated by normalization to body mass, suggests that a neurotoxic rather than a cytotoxic mechanism is killing the animals. The future use of cellular microsystems to replace animal experiments will motivate the development of new microsensors, as well as the consideration of newly accessible parameters in systems biology models.
authors.affiliation: University of Rostock, Biophysics, Gertrudenstraße 11a, 18057 Rostock, Germany. Electronic address: matthias.nissen@gmx.de.
authors.forename: Matthias
authors.initials: M
authors.lastname: Nissen
authors.affiliation: Leibniz Institute for Farm Animal Biology (FBN), Institute of Muscle Biology and Growth, Wilhelm-Stahl-Allee 2, 18196 Dummerstorf, Germany. Electronic address: buehler@fbn-dummerstorf.de.
authors.forename: Sebastian M
authors.initials: SM
authors.lastname: Buehler
authors.affiliation: University of Rostock, Biophysics, Gertrudenstraße 11a, 18057 Rostock, Germany. Electronic address: marco.stubbe@uni-rostock.de.
authors.forename: Marco
authors.initials: M
authors.lastname: Stubbe
authors.affiliation: University of Rostock, Biophysics, Gertrudenstraße 11a, 18057 Rostock, Germany. Electronic address: jan.gimsa@uni-rostock.de.
authors.forename: Jan
authors.initials: J
authors.lastname: Gimsa
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D003593:Cytoplasm / Q000187:drug effects / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005260:Female; D020128:Inhibitory Concentration 50; D051379:Mice; D009415:Nerve Net / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D011247:Pregnancy; D014635:Valproic Acid / Q000494:pharmacology*
chemical_list: D014635:Valproic Acid; D000255:Adenosine Triphosphate
keywords: Action potential rate; Hormesis; Micro electrode array; Micro fluidic cell culture systems; Neurotoxicity