Referenced in: none

Automatically associated channels: Kv11.1

Title: Variability in the measurement of hERG potassium channel inhibition: effects of temperature and stimulus pattern.

Authors: Glenn E Kirsch, Elena S Trepakova, Jessica C Brimecombe, Serguei S Sidach, Hope D Erickson, Mary C Kochan, Lisa M Shyjka, Antonio E Lacerda, Arthur M Brown

Journal, date & volume: , 2004 Sep-Oct , 50, 93-101

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/15385083

Abstract
In vitro evaluation of drug effects on hERG K(+) channels is a valuable tool for identifying potential proarrhythmic side effects in drug safety testing. Patch-clamp recording of hERG K(+) current in mammalian cells can accurately evaluate drug effects, but the methodology has not been standardized, and results vary widely. Our objective was to evaluate two potential sources of variability: the temperature at which recordings are performed and the voltage pulse protocol used to activate hERG K(+) channels expressed in HEK293 cells.A panel of 15 drugs that spanned a broad range of potency for hERG inhibition and pharmacological class was evaluated at both room and near-physiological temperatures using several patch-clamp voltage protocols. Concentration-response analysis was performed with three stimulus protocols: 0.5- and 2-s step pulses, or a step-ramp pattern.Block by 2 of the 15 drugs tested, d,l-sotalol (antiarrhythmic) and erythromycin (antibiotic), was markedly temperature sensitive. hERG inhibition measured using a 2-s step-pulse protocol underestimated erythromycin potency compared with results obtained with a step-ramp protocol. Using conservative acceptance criteria and the step-ramp protocol, the IC(50) values for hERG block differed by less than twofold for 15 drugs.Data obtained at near-physiological temperatures using a step-ramp pattern are highly repeatable and provide a conservative safety evaluation of hERG inhibition.