Related Experiment Videos
A new calcium current underlying the plateau of the cardiac action potential
Abstract:
A small and very slow inward calcium current has been identified in isolated single ventricular cells using TTX and Cd2+ to block the sodium and fast calcium currents. Activation requires about 300 ms at the threshold potential of -60 mV, decreasing to 80 ms at the peak current voltage of -30 mV. Inactivation is five to ten times longer. Half steady-state activation and inactivation are at -50 and -45 mV respectively. The current is distinctively different in both its kinetics and pharmacology from the conventional calcium current described in single heart cells. It is proposed that it contributes significant current to help maintain a major portion of the long ventricular action potential.
Insights
Researchers identified a novel, slow inward calcium current in heart ventricular cells. This distinct current, differing from known calcium channels, may significantly influence the ventricular action potential duration.
Area of Science:
- Cardiology
- Electrophysiology
- Molecular Biology
Background:
- Ventricular cells possess various ion channels crucial for cardiac function.
- Understanding calcium currents is vital for comprehending cardiac action potentials.
Purpose of the Study:
- To identify and characterize a novel, slow inward calcium current in isolated single ventricular cells.
- To differentiate this current from previously described calcium currents based on kinetics and pharmacology.
Main Methods:
- Utilized electrophysiological techniques on isolated single ventricular cells.
- Employed tetrodotoxin (TTX) and cadmium ions (Cd2+) to selectively block sodium and fast calcium currents, respectively.
- Analyzed current activation and inactivation kinetics and voltage dependence.
Main Results:
- A small, slow inward calcium current was identified with slow activation (300 ms at -60 mV to 80 ms at -30 mV) and prolonged inactivation (5-10 times longer than activation).
- Half-maximal steady-state activation and inactivation occurred at -50 mV and -45 mV, respectively.
- The current exhibited distinct kinetics and pharmacological properties compared to conventional cardiac calcium currents.
Conclusions:
- The identified slow inward calcium current is a novel electrophysiological entity in ventricular cells.
- This current likely plays a significant role in maintaining the prolonged ventricular action potential.
- Further research is warranted to elucidate the specific channels and physiological implications of this current.