title: Moles of a Substance per Cell Is a Highly Informative Dosing Metric in Cell Culture.
abstract: BACKGROUND
  The biological consequences upon exposure of cells in culture to a dose of xenobiotic are not only dependent on biological variables, but also the physical aspects of experiments e.g. cell number and media volume. Dependence on physical aspects is often overlooked due to the unrecognized ambiguity in the dominant metric used to express exposure, i.e. initial concentration of xenobiotic delivered to the culture medium over the cells. We hypothesize that for many xenobiotics, specifying dose as moles per cell will reduce this ambiguity. Dose as moles per cell can also provide additional information not easily obtainable with traditional dosing metrics.
  
  
  METHODS
  Here, 1,4-benzoquinone and oligomycin A are used as model compounds to investigate moles per cell as an informative dosing metric. Mechanistic insight into reactions with intracellular molecules, differences between sequential and bolus addition of xenobiotic and the influence of cell volume and protein content on toxicity are also investigated.
  
  
  RESULTS
  When the dose of 1,4-benzoquinone or oligomycin A was specified as moles per cell, toxicity was independent of the physical conditions used (number of cells, volume of medium). When using moles per cell as a dose-metric, direct quantitative comparisons can be made between biochemical or biological endpoints and the dose of xenobiotic applied. For example, the toxicity of 1,4-benzoquinone correlated inversely with intracellular volume for all five cell lines exposed (C6, MDA-MB231, A549, MIA PaCa-2, and HepG2).
  
  
  CONCLUSIONS
  Moles per cell is a useful and informative dosing metric in cell culture. This dosing metric is a scalable parameter that: can reduce ambiguity between experiments having different physical conditions; provides additional mechanistic information; allows direct comparison between different cells; affords a more uniform platform for experimental design; addresses the important issue of repeatability of experimental results, and could increase the translatability of information gained from in vitro experiments.
authors.affiliation: Interdisciplinary Graduate Program in Human Toxicology, The University of Iowa, Iowa City, Iowa, 52242, United States of America.
authors.forename: Claire M
authors.initials: CM
authors.lastname: Doskey
authors.affiliation: Interdisciplinary Graduate Program in Human Toxicology, The University of Iowa, Iowa City, Iowa, 52242, United States of America.
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: van 't Erve
authors.affiliation: Free Radical and Radiation Biology Program, Department of Radiation Oncology, The University of Iowa, Iowa City, Iowa, 52242, United States of America.
authors.forename: Brett A
authors.initials: BA
authors.lastname: Wagner
authors.affiliation: Interdisciplinary Graduate Program in Human Toxicology, The University of Iowa, Iowa City, Iowa, 52242, United States of America; Free Radical and Radiation Biology Program, Department of Radiation Oncology, The University of Iowa, Iowa City, Iowa, 52242, United States of America.
authors.forename: Garry R
authors.initials: GR
authors.lastname: Buettner
mesh_terms: D016227:Benzoquinones / Q000008:administration & dosage / Q000633:toxicity; D002452:Cell Count; D002460:Cell Line; D048429:Cell Size; D004305:Dose-Response Relationship, Drug; D004353:Drug Evaluation, Preclinical / Q000379:methods* / Q000706:statistics & numerical data; D005978:Glutathione / Q000378:metabolism; D056945:Hep G2 Cells; D006801:Humans; D008954:Models, Biological; D009840:Oligomycins / Q000008:administration & dosage / Q000633:toxicity; D009994:Osmolar Concentration; D011506:Proteins / Q000378:metabolism; D015203:Reproducibility of Results; D015262:Xenobiotics / Q000008:administration & dosage* / Q000633:toxicity
chemical_list: D016227:Benzoquinones; D009840:Oligomycins; D011506:Proteins; D015262:Xenobiotics; C031004:oligomycin A; C004532:quinone; D005978:Glutathione