Tags

Type your tag names separated by a space and hit enter

Investigating dynamic protocol-dependence of hERG potassium channel inhibition at 37 degrees C: Cisapride versus dofetilide.
J Pharmacol Toxicol Methods. 2010 Mar-Apr; 61(2):178-91.JP

Abstract

INTRODUCTION

Pharmacological inhibition of cardiac potassium channels encoded by hERG (human ether-à-go-go-related gene) is associated with QT interval prolongation and torsades de pointes arrhythmia. Electrophysiological assays of hERG channel inhibition are integral to the safety testing of novel drug candidates. This study was conducted to compare, for the high affinity hERG inhibitors dofetilide and cisapride, hERG blockade between action potential (AP) and conventional (step and step-ramp) screening waveforms. Furthermore, it evaluated dynamic (pulse-by-pulse) protocol-dependence of hERG channel inhibition by these drugs.

METHODS

Whole-cell patch-clamp recordings were made at 37 degrees C from hERG-expressing HEK 293 cells. Half-maximal inhibitory concentrations (IC(50) values) for I(hERG) blockade were obtained using conventional voltage clamp and action potential clamp, using previously digitised ventricular and Purkinje fibre (PF) AP waveforms.

RESULTS

A more marked variation in IC(50) values with different command waveforms was observed for cisapride (ranging from 7 to 72 nM) than for dofetilide (ranging from 4 to 15 nM), with higher IC(50)s obtained with AP than step or step-ramp commands. The two drugs differed little from one another in effects on voltage-dependent activation; however, I(hERG) blockade by each drug was initially voltage-dependent, but at steady-state was only voltage-dependent for cisapride. There was comparatively little difference between the two drugs in effects on I(hERG) availability or time constants of development of inactivation. Features of time-dependence of blockade and the use of protocols employing varying rest periods in drug or commands of alternating duration highlighted a pronounced ability of cisapride, but not dofetilide, to dissociate and reassociate from hERG on a pulse-by-pulse basis.

DISCUSSION

Protocols described here that demonstrated dynamic variation (drug dissociation/reassociation) in hERG channel current blockade at 37 degrees C for cisapride may have future value for investigating drug interactions with the hERG channel. Downloadable digitised ventricular and PF AP waveforms that can be used in AP clamp experiments also accompany this article.

Authors+Show Affiliations

Department of Physiology and Pharmacology, School of Medical Sciences, University Walk, Bristol, BS8 1TD, UK.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Comparative Study
Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

20172036

Citation

Milnes, James T., et al. "Investigating Dynamic Protocol-dependence of hERG Potassium Channel Inhibition at 37 Degrees C: Cisapride Versus Dofetilide." Journal of Pharmacological and Toxicological Methods, vol. 61, no. 2, 2010, pp. 178-91.
Milnes JT, Witchel HJ, Leaney JL, et al. Investigating dynamic protocol-dependence of hERG potassium channel inhibition at 37 degrees C: Cisapride versus dofetilide. J Pharmacol Toxicol Methods. 2010;61(2):178-91.
Milnes, J. T., Witchel, H. J., Leaney, J. L., Leishman, D. J., & Hancox, J. C. (2010). Investigating dynamic protocol-dependence of hERG potassium channel inhibition at 37 degrees C: Cisapride versus dofetilide. Journal of Pharmacological and Toxicological Methods, 61(2), 178-91. https://doi.org/10.1016/j.vascn.2010.02.007
Milnes JT, et al. Investigating Dynamic Protocol-dependence of hERG Potassium Channel Inhibition at 37 Degrees C: Cisapride Versus Dofetilide. J Pharmacol Toxicol Methods. 2010 Mar-Apr;61(2):178-91. PubMed PMID: 20172036.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Investigating dynamic protocol-dependence of hERG potassium channel inhibition at 37 degrees C: Cisapride versus dofetilide. AU - Milnes,James T, AU - Witchel,Harry J, AU - Leaney,Joanne L, AU - Leishman,Derek J, AU - Hancox,Jules C, Y1 - 2010/02/19/ PY - 2009/12/24/received PY - 2010/02/03/revised PY - 2010/02/11/accepted PY - 2010/2/23/entrez PY - 2010/2/23/pubmed PY - 2010/6/18/medline SP - 178 EP - 91 JF - Journal of pharmacological and toxicological methods JO - J Pharmacol Toxicol Methods VL - 61 IS - 2 N2 - INTRODUCTION: Pharmacological inhibition of cardiac potassium channels encoded by hERG (human ether-à-go-go-related gene) is associated with QT interval prolongation and torsades de pointes arrhythmia. Electrophysiological assays of hERG channel inhibition are integral to the safety testing of novel drug candidates. This study was conducted to compare, for the high affinity hERG inhibitors dofetilide and cisapride, hERG blockade between action potential (AP) and conventional (step and step-ramp) screening waveforms. Furthermore, it evaluated dynamic (pulse-by-pulse) protocol-dependence of hERG channel inhibition by these drugs. METHODS: Whole-cell patch-clamp recordings were made at 37 degrees C from hERG-expressing HEK 293 cells. Half-maximal inhibitory concentrations (IC(50) values) for I(hERG) blockade were obtained using conventional voltage clamp and action potential clamp, using previously digitised ventricular and Purkinje fibre (PF) AP waveforms. RESULTS: A more marked variation in IC(50) values with different command waveforms was observed for cisapride (ranging from 7 to 72 nM) than for dofetilide (ranging from 4 to 15 nM), with higher IC(50)s obtained with AP than step or step-ramp commands. The two drugs differed little from one another in effects on voltage-dependent activation; however, I(hERG) blockade by each drug was initially voltage-dependent, but at steady-state was only voltage-dependent for cisapride. There was comparatively little difference between the two drugs in effects on I(hERG) availability or time constants of development of inactivation. Features of time-dependence of blockade and the use of protocols employing varying rest periods in drug or commands of alternating duration highlighted a pronounced ability of cisapride, but not dofetilide, to dissociate and reassociate from hERG on a pulse-by-pulse basis. DISCUSSION: Protocols described here that demonstrated dynamic variation (drug dissociation/reassociation) in hERG channel current blockade at 37 degrees C for cisapride may have future value for investigating drug interactions with the hERG channel. Downloadable digitised ventricular and PF AP waveforms that can be used in AP clamp experiments also accompany this article. SN - 1873-488X UR - https://www.unboundmedicine.com/medline/citation/20172036/Investigating_dynamic_protocol_dependence_of_hERG_potassium_channel_inhibition_at_37_degrees_C:_Cisapride_versus_dofetilide_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S1056-8719(10)00023-7 DB - PRIME DP - Unbound Medicine ER -