title: Development of selective blockers for Ca²(+)-activated Cl channel using Xenopus laevis oocytes with an improved drug screening strategy.
abstract: BACKGROUND
  Ca²(+)-activated Cl⁻ channels (CaCCs) participate in many important physiological processes. However, the lack of effective and selective blockers has hindered the study of these channels, mostly due to the lack of good assay system. Here, we have developed a reliable drug screening method for better blockers of CaCCs, using the endogeneous CaCCs in Xenopus laevis oocytes and two-electrode voltage-clamp (TEVC) technique.
  
  
  RESULTS
  Oocytes were prepared with a treatment of Ca²(+) ionophore, which was followed by a treatment of thapsigargin which depletes Ca²(+) stores to eliminate any contribution of Ca²(+) release. TEVC was performed with micropipette containing chelerythrine to prevent PKC dependent run-up or run-down. Under these conditions, Ca²(+)-activated Cl⁻ currents induced by bath application of Ca²(+) to oocytes showed stable peak amplitude when repetitively activated, allowing us to test several concentrations of a test compound from one oocyte. Inhibitory activities of commercially available blockers and synthesized anthranilic acid derivatives were tested using this method. As a result, newly synthesized N-(4-trifluoromethylphenyl)anthranilic acid with trifluoromethyl group (-CF₃) at para position on the benzene ring showed the lowest IC₅₀.
  
  
  CONCLUSIONS
  Our results provide an optimal drug screening strategy suitable for high throughput screening, and propose N-(4-trifluoromethylphenyl)anthranilic acid as an improved CaCC blocker.
authors.affiliation: Center for Neural Science, Korea Institute of Science and Technology, Seoul, Republic of Korea. osj@kist.re.kr
authors.forename: Soo-Jin
authors.initials: SJ
authors.lastname: Oh
authors.forename: Jung Hwan
authors.initials: JH
authors.lastname: Park
authors.forename: Sungyu
authors.initials: S
authors.lastname: Han
authors.forename: Jae Kyun
authors.initials: JK
authors.lastname: Lee
authors.forename: Eun Joo
authors.initials: EJ
authors.lastname: Roh
authors.forename: C Justin
authors.initials: CJ
authors.lastname: Lee
mesh_terms: D000818:Animals; D001554:Benzene / Q000737:chemistry; D002118:Calcium / Q000378:metabolism; D018118:Chloride Channels / Q000037:antagonists & inhibitors* / Q000378:metabolism; D004353:Drug Evaluation, Preclinical / Q000379:methods*; D020128:Inhibitory Concentration 50; D015640:Ion Channel Gating / Q000187:drug effects; D015759:Ionomycin / Q000494:pharmacology; D049990:Membrane Transport Modulators / Q000032:analysis* / Q000494:pharmacology*; D009865:Oocytes / Q000187:drug effects* / Q000378:metabolism*; D010539:Permeability / Q000187:drug effects; D014982:Xenopus laevis / Q000378:metabolism*; D062367:ortho-Aminobenzoates / Q000138:chemical synthesis / Q000494:pharmacology
chemical_list: D018118:Chloride Channels; D049990:Membrane Transport Modulators; D062367:ortho-Aminobenzoates; C031385:anthranilic acid; D015759:Ionomycin; D001554:Benzene; D002118:Calcium