I NaCa andI Cl(Ca)contribute to isoproterenol-induced delayed afterdepolarizations in midmyocardial cells
| Autor: | Charlene M. Weigel, Andrew C. Zygmunt, Robert J. Goodrow |
|---|---|
| Rok vydání: | 1998 |
| Předmět: |
Male
Cardiotonic Agents Physiology Sodium chemistry.chemical_element Calcium Chloride Ion Channels Sodium-Calcium Exchanger Dogs Chlorides Cations Physiology (medical) Isoprenaline Reaction Time medicine Animals Ventricular Function Ouabain Calcium metabolism Chemistry Myocardium Electric Conductivity Isoproterenol Conductance Heart Depolarization Electrophysiology Biochemistry NACA Biophysics Cardiology and Cardiovascular Medicine medicine.drug |
| Zdroj: | American Journal of Physiology-Heart and Circulatory Physiology. 275:H1979-H1992 |
| ISSN: | 1522-1539 0363-6135 |
| Popis: | The contributions of electrogenic sodium/calcium exchange current ( I NaCa), calcium-activated chloride conductance [ I Cl(Ca)], and calcium-activated nonselective cation conductance to delayed afterdepolarizations (DAD) were examined. Nonselective cation channels were absent in canine M cells, since inhibition of I NaCa and I Cl(Ca)eliminated all calcium-activated currents without abolishing cell shortening. After the cells were treated with isoproterenol and ouabain to increase calcium loading, I NaCa was 168 ± 30 × 10−3 pC/pF and I Cl(Ca) was 114 ± 24 × 10−3pC/pF. Transient overlapping inward and outward currents were evoked positive to the chloride reversal potential ( E Cl). Outward current was chloride sensitive, and inward current was blocked by replacement of external sodium with lithium. When E Cl was −50 mV, triggered activity occurred in normal external sodium and persisted after inhibition of I NaCa. Steps to −80 mV revealed oscillating inward currents in normal sodium and chloride, which persisted after inhibition of I NaCa. When E Cl was equal to −113 mV, I Cl(Ca) opposed I NaCa at the resting potential. DAD occurred in normal sodium, and inhibition of outward I Cl(Ca)provoked triggered activity. We conclude that I NaCa represents ∼60% of the total calcium-activated current at resting potentials but that both I NaCa and I Cl(Ca) work in concert to cause DAD in calcium-overloaded cells. |
| Databáze: | OpenAIRE |
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