Characterization of the sodium current in single human atrial myocytes
| Autor: | Hongjun Jia, C. E. Arentzen, J. A. Wasserstrom, Y. Sakakibara, R S Hartz, T. Furukawa, Donald H. Singer |
|---|---|
| Rok vydání: | 1992 |
| Předmět: |
Adult
medicine.medical_specialty Adolescent Heart Diseases Physiology Sodium Kinetics chemistry.chemical_element Tetrodotoxin Sodium Channels Membrane Potentials chemistry.chemical_compound medicine Humans Myocyte Heart Atria Child Reversal potential Aged Binding Sites Dose-Response Relationship Drug Myocardium Pipette Middle Aged Surgery Electrophysiology Dose–response relationship chemistry Child Preschool Biophysics Cardiology and Cardiovascular Medicine |
| Zdroj: | Circulation Research. 71:535-546 |
| ISSN: | 1524-4571 0009-7330 |
| DOI: | 10.1161/01.res.71.3.535 |
| Popis: | Patch-clamp recording techniques have permitted measurement of the fast Na+ current (INa) in isolated cardiac cells from a number of species in recent years. However, there is still only very little information concerning human cardiac INa. The purpose of this study was to describe the kinetics of INa in normal-appearing, Ca(2+)-tolerant, enzymatically isolated human atrial myocytes using whole-cell voltage-clamp techniques. Atrial specimens were obtained from 46 patients undergoing open heart surgery. Cs+ was substituted for K+ in both pipette and external solutions and F- was added to the former. The reversal potential of the rapid inward current varied approximately 57 mV at 17 +/- 1 degrees C with a 10-fold change in [Na+]o, and the current was completely blocked by 100 microM tetrodotoxin, findings typical of the fast cardiac Na+ current. The tetrodotoxin dose-response curve was best fitted by an equation describing binding to high- and low-affinity sites. INa was activated at a voltage threshold of -70 to -60 mV, and peak inward current was obtained at approximately -30 mV (holding potential, -140 mV). The inactivation time course was voltage dependent and was fitted best by the sum of two exponentials. The relation between voltage and steady-state availability (h infinity) was sigmoidal with the half-inactivation at -95.8 +/- 0.9 mV and a slope factor of 5.3 +/- 0.1 mV (n = 46), and we did not observe a significant difference with disease and age. The overlap of the h infinity and activation curves suggested the presence of a Na+ "window" current. Recovery from inactivation also was voltage dependent and best fitted by a model describing the sum of two exponentials. Recovery occurred after an initial delay at potentials positive to -140 mV, suggesting that inactivation of human atrial INa is a multistate process. We conclude that INa of normal-appearing, Ca(2+)-tolerant human atrial myocytes is similar to that of other mammalian cardiac cells with the possible exception of having two tetrodotoxin binding sites. |
| Databáze: | OpenAIRE |
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