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Single-channel properties of L-type calcium channels from failing human ventricle
R Handrock1, F Schröder, S Hirt
1Department of Pharmacology, University of Cologne, Germany.
Insights
Single-channel recordings of L-type calcium channels in human failing hearts are feasible. These channels exhibit properties comparable to animal models, paving the way for future heart failure research.
Area of Science:
- Cardiovascular Physiology
- Molecular Cardiology
- Ion Channel Biophysics
Background:
- Heart failure is a complex condition affecting cardiac function.
- L-type calcium channels play a critical role in cardiac excitation-contraction coupling.
- Understanding these channels in failing human hearts is crucial for therapeutic development.
Purpose of the Study:
- To analyze single-channel properties of L-type calcium channels in failing human hearts.
- To compare human data with existing animal models.
- To assess the feasibility of future single-channel studies in heart failure pathophysiology.
Main Methods:
- Utilized the patch-clamp technique in the cell-attached configuration.
- Recorded single L-type calcium channel activity from ventricular myocytes of explanted failing human hearts.
- Analyzed channel conductance and gating kinetics.
Main Results:
- Successful single-channel recordings were obtained in 11 out of 19 human heart samples.
- Mean single-channel conductance was determined under control and agonist-stimulated conditions.
- Gating analysis revealed distinct rapid and slow gating schemes, with significant clustering of active/inactive sweeps.
Conclusions:
- Single-channel measurements of L-type calcium channels in human failing ventricles are feasible and reproducible.
- Channel properties are qualitatively similar to those observed in other mammalian species.
- Further studies are warranted to explore potential quantitative differences related to heart failure.
Objective:
The aim of our study was to analyse the single-channel properties of L-type calcium channels from failing human heart and to compare them to the respective animal data. Furthermore, we intended to evaluate the feasibility of future single-channel studies on the role of calcium channels in the pathophysiology of heart failure.
Methods:
Single L-type calcium channels were recorded in ventricular myocytes from explanted failing human heart, using the cell-attached configuration of the patch-clamp technique.
Results:
One or more successful registrations of calcium channels could be obtained in 11 of 19 cell isolations. Determination of single-channel conductance yielded a mean value of 16.6 +/- 1.2 pS (70 mM Ba2+ as the charge carrier) under control conditions and 23.7 +/- 2.8 pS in presence of the calcium-channel agonist FPL 64176. The rapid gating process could be described by a C<-->C<-->O gating scheme. Slow gating analysis revealed a highly significant clustering of active and non-active sweeps.
Conclusion:
Single-channel measurements of L-type calcium channels in human failing ventricle are feasible and reproducible despite the varying patient characteristics. Their channel properties are qualitatively comparable to those found in other mammals. Whether there are quantitative differences due to the underlying heart failure can be elucidated in further studies.