Abstract
A whole-cell early transient outward current occurs in rat myoballs if and only if there is an immediatly preceding current of large amplitude through the voltage-gated, tetrodotoxin-inhibitable Na+ channel. This early outward transient is a K+ current, designated I K(Na+). Under the conditions in which I K(Na+) appears, simultaneous measurement of voltage and current, under voltage clamp, demonstrates that there is transient voltage escape to depolarized levels, peaking at about the time of peak inward Na+ current arid resembling an action potential. I K(Na+) was never seen in the absence of this breach of the voltage clamp, suggesting that I K(Na+) might be an artefact due to transient depolarization from the clamp. However, when the voltage escape was mimicked by voltage commands under conditions in which the Na+ channel was not activated, there was no I K(Na). Insulin increased or produced I K(Na+) even though insulin had no effect on I Na or on the delayed rectifier K+ current or on the escape from voltage clamp. It is concluded that there is a population of rat myoballs in which there is an early outward K+ current that requires an immediately preceding current through the voltagegated tetrodotoxin-inhibitable Na+ channel and is enhanced by insulin.
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Zierler, K., Wu, F.S. An early outward transient K+ current that depends on a preceding Na+ current and is enhanced by insulin. Pflügers Arch 422, 267–272 (1992). https://doi.org/10.1007/BF00376212
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DOI: https://doi.org/10.1007/BF00376212