Temperature dependent hERG channel pharmacology and kinetics on the IonFluxTM system
The human ether-a-go-go-related gene (hERG) encodes a K+ delayed rectifier channel that plays a critical role in the control of action potential repolarization in mammalian and human cardiac myocytes. Therapeutic compounds from a variety of chemical classes can potently block the hERG channel and cause the prolongation of the electrocardiographic QT interval, which may result in potentially fatal ventricular arrhythmia, torsade de pointes (TdP). A risk of TdP is one of the major causes of drug withdrawals from the market by regulatory agencies and pharmaceutical companies (Trudeau, M. C. 1995, Sanguinetti M. C. 1995).
The patch clamp technique is the gold standard in evaluating the inhibitory potential of a compound using in vitro hERG assays. Although technically more difficult, patch-clamp recording at the near physiological temperature is better suited for drug safety testing than room temperature because the temperature dependent process can contribute to the steady state inhibition of hERG channels. Reported data has showed that increased temperature accelerated the hERG activation, inactivation, recovery from inactivation, and deactivation kinetics, as well as steady-state level inhibition (Zhou, Z. 1998). Studies have also shown that some compounds were markedly temperature sensitive and showed significant potency shift at physiological temperature (Sale, H. 2008, Kirsch, G. E, 2004). Therefore, it is desirable to conduct functional hERG screening at physiological temperature. Automated patch clamp systems can achieve higher throughput than the conventional manual patch clamp and are less labor intensive, which allow greater capacity to conduct early stage functional hERG screening. However, the first generation of automated patch clamp systems to enter the market have been limited to room temperature screening only.
To address this need, the IonFlux system integrates a temperature control module, enabling users to perform temperature dependent electrophysiology screening assays. In this report, we present pharmacology and kinetic data from the hERG channel, comparing room temperature to physiological temperature recordings on the IonFlux platform.
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