Experimental physiology
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Experimental physiology · Jul 1996
Separation of the components of the delayed rectifier potassium current using selective blockers of IKr and IKs in guinea-pig isolated ventricular myocytes.
Delayed rectifier potassium current (IK) was investigated in guinea-pig isolated ventricular myocytes under voltage-clamp conditions ('switched' single electrode clamp), using selective blockers and/or different activation protocols to separate its rapid (IKr) and slow (IKs) components. The class III antiarrhythmic compound E4031 (5 microM) was used to block IKr and the anaesthetic drugs propofol (100 microM) or thiopentone (100 microM) to block IKs. In all experiments L-type calcium currents were blocked with nifedipine (2 microM). ⋯ Forskolin (1 microM) enhanced the current most consistent with IKs. Propofol (300 microM) caused a 64 +/- 3% increase in action potential duration in the presence of both E4031 (5 microM) and nifedipine (2 microM), consistent with an important role for IKs in the repolarization of the action potential in the guinea-pig heart. The observations therefore provide further support for separate components of IK with different characteristics in the guinea-pig heart; it appears that E4031 and propofol or thiopentone are useful complementary tools for their separation.