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|Title:||Hypoxia increases persistent sodium current in rat ventricular myocytes|
|Citation:||Journal of Physiology, 1996; 497(2):337-347|
|Publisher:||The Physiological Society|
|Y.-K. Ju, D. A. Saint, and P. W. Gage|
|Abstract:||1. A persistent inward current activated by depolarization was recorded using the whole-cell, tight seal technique in rat isolated cardiac myocytes. The amplitude of the inward current increased when cells were exposed to a solution with low oxygen tension. 2. The persistent inward current had the characteristics of the persistent Na+ current described previously in rat ventricular myocytes: it was activated at negative potentials (-70 mV), reversed close to the equilibrium potential for Na+ (ENa), was blocked by TTX and was resistant to inactivation. 3. Persistent single Na+ channel currents activated by long (200-400 ms) depolarizations were recorded in cell-attached patches on isolated ventricular myocytes. Hypoxia increased the frequency of opening of the persistent Na+ channels. 4. Persistent Na+ channels recorded during hypoxia had characteristics similar to those of persistent Na+ channels recorded at normal oxygen tensions. They had a null potential at ENa, their amplitude varied with [Na+], they were resistant to inactivation and their mean open time increased with increasing depolarization. 5. The persistent Na+ channels in cell-attached patches were blocked by TTX (50 microM) in the patch pipette and by lidocaine (100 microM). 6. It was concluded that hypoxia increases the open probability of TTX-sensitive, inactivation-resistant Na+ channels. The voltage dependence of these channels, and their greatly increased activity during hypoxia, suggest that they may play an important role in the generation of arrhythmias during hypoxia.|
|Keywords:||Myocardium; Heart Ventricles; Animals; Rats; Rats, Wistar; Sodium; Lidocaine; Tetrodotoxin; Sodium Channels; Anti-Arrhythmia Agents; Electrophysiology; Ion Channel Gating; Membrane Potentials; Time Factors; Hypoxia|
|Appears in Collections:||Physiology publications|
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