title: Dimethyl sulfoxide effects on hERG channels expressed in HEK293 cells.
abstract: BACKGROUND
  Dimethyl sulfoxide (DMSO) is widely used as a solvent to facilitate formulation of test substances in cell perfusion solutions. However, DMSO concentration in bath (extracellular) solution is usually limited to 0.1-0.3% to avoid DMSO-induced changes in cell morphology and membrane properties due to elevation of osmolality. The purpose of this study was to examine whether DMSO-induced hyperosmotic effects on hERG expressing cells could be compensated by adding an equivalent amount of DMSO in pipette (intracellular) solution, to investigate DMSO effects on hERG channels, and to determine the impact of DMSO on the potency of hERG channel blockers.
  
  
  METHODS
  Whole-cell patch clamp method was used to record hERG currents in HEK293 cells. DMSO at concentrations of 0.1% to 2% was applied to bath and pipette solutions. Various voltage protocols were used to examine DMSO effects on hERG channel properties and to evaluate DMSO impacts on the potency of terfenadine and E-4031.
  
  
  RESULTS
  When DMSO was added simultaneously in bath and pipette solutions, normal cell morphology and the proper current recording conditions could be maintained with application of up to 2% DMSO. DMSO slightly shifted the current-voltage relationship, activation curve, and inactivation curve of the hERG channel to more positive voltages. DMSO had little effect on the concentration-response relationship of hERG channel blockers we assessed. The IC50 for terfenadine and E-4031 were not significantly changed in the presence of 0.3, 0.5, 1 and 2% DMSO.
  
  
  CONCLUSIONS
  Our results demonstrate that changes in cell morphology induced by extracellular DMSO can be prevented by application of DMSO in pipette solution. By utilizing this approach, we successfully performed hERG current recordings using bath solution containing up to 2% DMSO. DMSO-induced shifts of the voltage-dependence of hERG channel gating had little impact on the potency of hERG channel blockers.
authors.affiliation: Aptuit, Inc., Preclinical Technologies, 10245 Hickman Mills Drive, Kansas City, MO 64137, USA.
authors.forename: Xiaoyi
authors.initials: X
authors.lastname: Du
authors.forename: Daniel
authors.initials: D
authors.lastname: Lu
authors.forename: Eric D
authors.initials: ED
authors.lastname: Daharsh
authors.forename: Aizhen
authors.initials: A
authors.lastname: Yao
authors.forename: Rebecca
authors.initials: R
authors.lastname: Dewoody
authors.forename: Jian-An
authors.initials: JA
authors.lastname: Yao
mesh_terms: D000465:Algorithms; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology; D002460:Cell Line; D004121:Dimethyl Sulfoxide / Q000633:toxicity*; D004305:Dose-Response Relationship, Drug; D000072237:ERG1 Potassium Channel; D004594:Electrophysiology; D051638:Ether-A-Go-Go Potassium Channels / Q000096:biosynthesis / Q000187:drug effects*; D006634:Histamine H1 Antagonists / Q000494:pharmacology; D006801:Humans; D009994:Osmolar Concentration; D018408:Patch-Clamp Techniques; D010880:Piperidines / Q000494:pharmacology; D026902:Potassium Channel Blockers / Q000494:pharmacology*; D011725:Pyridines / Q000494:pharmacology; D012997:Solvents / Q000633:toxicity*; D016593:Terfenadine / Q000494:pharmacology
chemical_list: D000889:Anti-Arrhythmia Agents; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; D006634:Histamine H1 Antagonists; C000606913:KCNH2 protein, human; D010880:Piperidines; D026902:Potassium Channel Blockers; D011725:Pyridines; D012997:Solvents; C063968:E 4031; D016593:Terfenadine; D004121:Dimethyl Sulfoxide