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K+ currents activated by depolarization in cardiac fibroblasts
Yoshiyuki Shibukawa1, E Lisa Chilton, K Andrew Maccannell
1Department of Physiology and Biophysics, Faculty of Medicine, University of Calgary, Alberta, Canada.
Biophysical Journal
|March 15, 2005
Summary
This study characterizes a specific potassium (K+) current in rat ventricular fibroblasts using patch-clamp electrophysiology. Findings reveal its voltage-dependent activation and inactivation, modulated by extracellular potassium levels.
Area of Science:
- Electrophysiology
- Cardiovascular Physiology
- Ion Channel Biology
Background:
- Ventricular fibroblasts play roles in cardiac structure and function.
- Understanding ion channel activity in fibroblasts is crucial for cardiac electrophysiology.
Purpose of the Study:
- To characterize the properties of K+ currents in rat ventricular fibroblasts.
- To investigate the voltage-dependence, kinetics, and modulation of these currents.
Main Methods:
- Whole-cell patch-clamp recordings were used.
- Experiments involved voltage-step protocols and varying extracellular K+ concentrations.
- Pharmacological agents like tetraethylammonium, dendrotoxin-I, and rTityustoxin Kalpha were employed.
Main Results:
- A time- and voltage-dependent outward K+ current was identified, activating at potentials positive to -30 mV.
- Current kinetics showed strong voltage dependence and were fitted by single exponential functions.
- Extracellular K+ concentration modulated steady-state inactivation, shifting the V(0.5) and affecting inactivation/recovery rates, suggesting C-type inactivation.
- The current was sensitive to dendrotoxin-I and rTityustoxin Kalpha.
Conclusions:
- Rat ventricular fibroblasts express a distinct K+ current with specific electrophysiological properties.
- Extracellular K+ concentration significantly influences the inactivation mechanisms of this current.
- The findings contribute to understanding fibroblast electrophysiology and potential roles in cardiac function.