title: Effects of chromanol 293B on transient outward and ultra-rapid delayed rectifier potassium currents in human atrial myocytes.
abstract: It is unclear whether chromanol 293B, a selective inhibitor of slow component of delayed rectifier K(+) current (I(Ks)), may affect other K(+) currents in human atrium. With whole-cell patch configuration, we evaluated effects of 293B on transient outward K(+) current (I(to1)) and ultra-rapid delayed rectifier K(+) current (I(Kur)) in isolated human atrial myocytes. It was found that 293B inhibited I(to1) and I(Kur) in a concentration-dependent manner. At 10 microM 293B suppressed I(to1) to 3.4 +/- 0.4 from 5.1 +/- 0.3 pA/pF (P < 0.01), and I(Kur) to 1.5 +/- 0.2 from 2.1 +/- 0.3 pA/pF (P < 0.01) at +50 mV. The inhibition of I(to1) and I(Kur) was independent of depolarizing voltage, and the concentration of 50% inhibition was 31.2 microM for I(to1), and 30.9 microM for I(Kur). 293B blocked I(to1) and I(Kur) with the same concentration range, and the significant effect was observed from the concentration of 1 microM. The maximum inhibitive effect was 88% for I(to1) and 96% for I(Kur) at 250 microM. Voltage dependence of activation and inactivation, and time-dependent recovery from inactivation of I(to1) were not altered by 293B; however, time to peak and time-dependent inactivation of I(to1) was significantly accelerated. The results indicate that 293B significantly inhibits the major repolarization K(+) currents I(to1) and I(Kur) in human atrial myocytes.
authors.affiliation: Institute of Cardiovascular Science and Medicine, Department of Medicine, University of Hong Kong, SAR, Hong Kong, China.
authors.forename: Xin-Ling
authors.initials: XL
authors.lastname: Du
authors.forename: Chu-Pak
authors.initials: CP
authors.lastname: Lau
authors.forename: Shui-Wah
authors.initials: SW
authors.lastname: Chiu
authors.forename: Hung-Fat
authors.initials: HF
authors.lastname: Tse
authors.forename: Uwe
authors.initials: U
authors.lastname: Gerlach
authors.forename: Gui-Rong
authors.initials: GR
authors.lastname: Li
mesh_terms: D000328:Adult; D000368:Aged; D002478:Cells, Cultured; D002839:Chromans / Q000494:pharmacology*; D051668:Delayed Rectifier Potassium Channels; D006325:Heart Atria / Q000166:cytology*; D006801:Humans; D008564:Membrane Potentials; D008875:Middle Aged; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers / Q000494:pharmacology*; D015221:Potassium Channels / Q000502:physiology*; D024683:Potassium Channels, Tandem Pore Domain; D024642:Potassium Channels, Voltage-Gated; D013449:Sulfonamides / Q000494:pharmacology*
chemical_list: D002839:Chromans; D051668:Delayed Rectifier Potassium Channels; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024683:Potassium Channels, Tandem Pore Domain; D024642:Potassium Channels, Voltage-Gated; D013449:Sulfonamides; C103474:6-cyano-4-(N-ethylsulfonyl-N-methylamino)-3-hydroxy-2,2-dimethylchromane