Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
8475013 | Journal of Molecular and Cellular Cardiology | 2013 | 24 Pages |
Abstract
The objective of this work is to examine the contribution of late Na+ current (INa,L) to the cardiac action potential (AP) and arrhythmogenic activities. In spite of the rapidly growing interest toward this current, there is no publication available on experimental recording of the dynamic INa,L current as it flows during AP with Ca2Â + cycling. Also unknown is how the current profile changes when the Ca2Â +-calmodulin dependent protein kinase II (CaMKII) signaling is altered, and how the current contributes to the development of arrhythmias. In this study we use an innovative AP-clamp Sequential Dissection technique to directly record the INa,L current during the AP with Ca2Â + cycling in the guinea pig ventricular myocytes. First, we found that the magnitude of INa,L measured under AP-clamp is substantially larger than earlier studies indicated. CaMKII inhibition using KN-93 significantly reduced the current. Second, we recorded INa,L together with IKs, IKr, and IK1 in the same cell to understand how these currents counterbalance to shape the AP morphology. We found that the amplitude and the total charge carried by INa,L exceed that of IKs. Third, facilitation of INa,L by Anemone toxin II prolonged APD and induced Ca2Â + oscillations that led to early and delayed afterdepolarizations and triggered APs; these arrhythmogenic activities were eliminated by buffering Ca2Â + with BAPTA. In conclusion, INa,L contributes a significantly large inward current that prolongs APD and unbalances the Ca2Â + homeostasis to cause arrhythmogenic APs.
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Authors
Balazs Horvath, Tamas Banyasz, Zhong Jian, Bence Hegyi, Kornel Kistamas, Peter P. Nanasi, Leighton T. Izu, Ye Chen-Izu,