Validation of a [3H]astemizole binding assay in HEK293 cells expressing HERG K+ channels

J Pharmacol Sci. 2004 Jul;95(3):311-9. doi: 10.1254/jphs.fpe0040101.


A radioligand binding assay for the HERG (human ether-a-go-go-related gene) K(+) channel was developed to identify compounds which may have inhibitory activity and potential cardiotoxicity. Pharmacological characterization of the [(3)H]astemizole binding assay for HERG K(+) channels was performed using HERG-expressing HEK293 cells. The assay conditions employed yielded 90% specific binding using 10 microg/well of membrane protein with 1.5 nM of [(3)H]astemizole at 25 degrees C. The K(d) and B(max) values were 5.91 +/- 0.81 nM and 6.36 +/- 0.26 pmol/mg, respectively. The intraassay and interassay variations were 11.4% and 14.9%, respectively. Binding affinities for 32 reference compounds (including dofetilide, cisapride, and terfenadine) with diverse structures demonstrated a similar potency rank order for HERG inhibition to that reported in the literature. Moreover, the [(3)H]astemizole binding data demonstrated a rank order of affinity that was highly correlated to that of inhibitory potency in the electrophysiological studies for HERG in HEK293 (r(SP) = 0.91, P<0.05). In conclusion, the [(3)H]astemizole binding assay is rapid and capable of detecting HERG inhibitors.

Publication types

  • Comparative Study

MeSH terms

  • Astemizole / metabolism
  • Astemizole / pharmacology*
  • Binding Sites
  • Binding, Competitive
  • Calcium Channel Blockers / metabolism
  • Calcium Channel Blockers / pharmacology*
  • Cell Line
  • ERG1 Potassium Channel
  • Ether-A-Go-Go Potassium Channels
  • Humans
  • Ligands
  • Patch-Clamp Techniques
  • Potassium Channels, Voltage-Gated / metabolism*
  • Radioligand Assay
  • Time Factors
  • Transfection
  • Tritium


  • Calcium Channel Blockers
  • ERG1 Potassium Channel
  • Ether-A-Go-Go Potassium Channels
  • KCNH2 protein, human
  • Ligands
  • Potassium Channels, Voltage-Gated
  • Tritium
  • Astemizole