Related Experiment Videos
Regional differences in calcium-release channels from heart
L Borgatta1, J Watras, A M Katz
1Department of Medicine, University of Connecticut, Farmington 06030.
Insights
Cardiac intracellular channels show regional specialization. The interventricular septum has unique calcium channels differing in conductance and gating kinetics from those in the left-ventricular free wall.
Area of Science:
- Cardiovascular Physiology
- Cellular Electrophysiology
- Molecular Cardiology
Background:
- The heart comprises diverse cell types with specialized functions.
- Intracellular ion channels are crucial for cardiac function and exhibit regional variations.
Purpose of the Study:
- To investigate regional specialization of intracellular channels in the heart.
- To characterize differences in calcium channels between the interventricular septum and left-ventricular free wall.
Main Methods:
- Electrophysiological recordings of intracellular channels from cardiac tissues.
- Characterization of channel conductance, open/closed times, and activation/inhibition properties.
- Comparison of channels from the interventricular septum and left-ventricular free wall.
Main Results:
- Cardiac calcium-release channels (ryanodine receptors) exhibit regional differences in conductance and gating kinetics.
- A distinct, smaller conductance (17 pS) calcium-permeable channel, similar to the inositol 1,4,5-trisphosphate-gated channel, was identified in the septum.
- The ryanodine receptor from the septum showed smaller conductance (31 pS vs. 100 pS) and longer open/closed times compared to the left-ventricular free wall.
Conclusions:
- Intracellular calcium channels display significant regional specialization within the heart.
- The identified inositol 1,4,5-trisphosphate-activated channel in the septum may originate from specialized conducting tissue.
- Ryanodine receptors in the septum and free wall likely derive from regionally specialized myocardial cells.
Abstract:
The heart is a heterogeneous tissue composed of several cell types tailored for specialized functions. We found that intracellular channels also exhibit regional specialization. In cardiac and skeletal muscle these channels are called the calcium-release channel and are identified by activation with either calcium or caffeine and inhibition by the hexavalent cation ruthenium red. The calcium-release channel of the sarcoplasmic reticulum from the interventricular septum has a smaller conductance (31 pS vs. 100 pS) and has longer open and closed times when compared with the channel from left-ventricular free wall. An additional calcium-permeable channel with an even smaller conductance (17 pS) was found in the septum, and this channel is similar to the inositol 1,4,5-trisphosphate-gated channel from smooth muscle and different from the calcium-release channel (ryanodine receptor) from skeletal and cardiac muscle. The inositol 1,4,5-trisphosphate-activated channel may be derived from specialized conducting tissue that is relatively abundant in the septum, whereas the other calcium-release channels may be derived from regionally specialized myocardial cells in the septum and free wall.