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Outward currents underlying repolarization in human atrial myocytes
1Department of Medical Physiology, University of Calgary School of Medicine, Alta., Canada.
Cardiovascular Research
|July 1, 1995
Summary
This study identified transient and sustained outward potassium currents in human atrial cells, crucial for action potential repolarization. Findings link electrophysiology to the molecular biology of human heart potassium channels.
Area of Science:
- Cardiology
- Electrophysiology
- Molecular Biology
Background:
- Human atrial myocytes possess complex outward potassium (K+) currents essential for cardiac action potential repolarization.
- Understanding these currents is vital for relating electrophysiological findings to the molecular basis of human heart function.
Purpose of the Study:
- To identify and characterize outward K+ currents active during the action potential plateau in human atrial myocytes.
- To compare these identified currents with known cloned K+ channels from human cDNA libraries.
Main Methods:
- Enzymatic isolation of single myocytes from human right atrial appendages.
- Whole-cell voltage- and current-clamp recording techniques were employed.
- Pharmacological (4-aminopyridine) and voltage-clamp protocols were used to separate and analyze K+ current components.
Main Results:
- Outward K+ current comprised transient (I(t)) and sustained components; 4-aminopyridine blocked the Ca(2+)-independent I(t).
- I(t) inactivated rapidly with depolarizing pre-pulses, while the sustained component showed slow inactivation.
- Reactivation of I(t) was dependent on extracellular potassium concentration ([K+]o).
Conclusions:
- The study provides insights into the ionic mechanisms of early and late repolarization in human atrial cells.
- Results bridge electrophysiological observations with molecular biology of human cardiac potassium channels.