Voltage Clamp Studies on Potassium Channels

Potassium channels represent a very large and diverse collection of membrane proteins which participate in important cellular functions regulating neuronal and cardial electrical patterns, release of neurotransmitters, muscle contractility, hormone secretion, secretion of fluids, and modulation of signal transduction pathways. Main categories of potassium channels are gated by voltage or an increase of intracellular calcium concentration (Escande and Henry 1993 Kaczorowski and Garcia 1999 Alexander et al. 2001). 

Inhibitors of the slow component Iks were developed in order to circumvent the negative rate dependence of IKr blockers on the effective refractory period (Busch et al. 1996 Suessbrich et al. 1996, 1997 Bosch et al. 1998). Gogelein et al. (2000) studied the effects of a potent inhibitor of Iks channels in Xenopus oocytes and guinea pig ventricular myocytes. 

Studies in Xenopus oocytes are performed with the two microelectrode voltage clamp method. For isolation of the oocytes, the toads are anesthetized using a 1 g/1 solution of 3-aminobenzoic acid ethyl ester and placed on ice. A small incision is made to retrieve sacs of oocytes and is subsequently closed with absorbable surgical suture. On waking up, the toads are placed back into the aquarium. The ovaries are cut up into small pieces and the oocytes are washed in Ca2+-free Or-2 solution (82.5 mM NaCl, 2mM KC1, ImM MgCb, 5 mM HEPES pH 7.4) and subsequently col- 

Alexander S, Peters J, Mathie A et al. (2001) TiPS Nomenclature Supplement 2001 

Carmeliet A, Mubagawa K (1998) Antiarrhythmic drugs and cardiac ion channels mechanism of action. Progr Biophys Mol Biol 70 1-71 

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