INTRODUCTION: 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. METHODS: 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. RESULTS: 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. DISCUSSION: Data obtained at near-physiological temperatures using a step-ramp pattern are highly repeatable and provide a conservative safety evaluation of hERG inhibition.
INTRODUCTION: 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. METHODS: 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. RESULTS: 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. DISCUSSION: Data obtained at near-physiological temperatures using a step-ramp pattern are highly repeatable and provide a conservative safety evaluation of hERG inhibition.
Authors: Roope Männikkö; G Overend; C Perrey; C L Gavaghan; J-P Valentin; J Morten; M Armstrong; C E Pollard Journal: Br J Pharmacol Date: 2009-08-10 Impact factor: 8.739
Authors: A S Bass; B Darpo; A Breidenbach; K Bruse; H S Feldman; D Garnes; T Hammond; W Haverkamp; C January; J Koerner; C Lawrence; D Leishman; D Roden; J P Valentin; M A Vos; Y-Y Zhou; T Karluss; P Sager Journal: Br J Pharmacol Date: 2008-08 Impact factor: 8.739
Authors: Qinlian Zhou; Andrew C Zygmunt; Jonathan M Cordeiro; Fernando Siso-Nadal; Robert E Miller; Gregery T Buzzard; Jeffrey J Fox Journal: Ann Biomed Eng Date: 2009-04-08 Impact factor: 3.934