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Intact Heart Loose Patch Photolysis Reveals Ionic Current Kinetics During Ventricular Action Potentials
Josefina Ramos-Franco1, Yuriana Aguilar-Sanchez1, Ariel L Escobar2
1From the Department of Molecular Biophysics and Physiology, Rush University Medical Center, Chicago, IL (J.R.-F.); and Quantitative Systems Biology Program, School of Natural Sciences (Y.A.-S.) and Biological Engineering and Small Scale Technologies Program, School of Engineering (A.L.E.), University of California, Merced, CA.
Circulation Research
|November 14, 2015
Summary
This study used loose patch photolysis to measure ionic currents in intact hearts, revealing L-type calcium channel current in phase 1 and Na+-Ca2+ exchanger current in phase 2 of the action potential.
Area of Science:
- Cardiovascular Physiology
- Cardiac Electrophysiology
- Molecular Cardiology
Background:
- Understanding cardiac action potential (AP) ionic currents is crucial for cardiovascular research.
- The loose patch photolysis technique offers novel insights into whole-heart function in health and disease.
Purpose of the Study:
- To measure transmembrane ionic currents during an AP in intact hearts.
- To elucidate the role of Ca(2+) influx in triggering Ca(2+)-induced Ca(2+) release.
- To determine how Ca(2+)-activated conductances contribute to AP phase 2.
Main Methods:
- Utilized the loose patch photolysis technique for ionic current measurement in intact hearts.
- Employed nifedipine photodegradation to activate voltage-dependent Ca(2+) conductance.
- Analyzed ionic currents during a mouse ventricular AP, identifying early and late components.
Main Results:
- Loose patch photolysis successfully measured transmembrane ionic currents in intact hearts.
- The early component of the ventricular AP was attributed to L-type Ca(2+) channel (CaV 1.2) influx.
- The late component was identified as Na(+)-Ca(2+) exchanger current, driven by sarcoplasmic reticulum Ca(2+) release.
Conclusions:
- The novel loose patch photolysis technique enabled dissection of ionic currents in the intact heart.
- L-type Ca(2+) current contributes to AP phase 1, while Na(+)-Ca(2+) exchanger contributes to phase 2.
- L-type Ca(2+) channel current terminates due to voltage-dependent deactivation, not Ca(2+)-dependent inactivation.
Keywords:
action potentialscalcium signalingexcitation contraction couplingionic currentsnifedipinesarcoplasmic reticulumMore Related Videos
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