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Single cardiac sarcoplasmic reticulum Ca2+-release channel: activation by caffeine
1Department of Biochemistry, University of North Carolina, Chapel Hill 27599-7260.
The American Journal of Physiology
|February 1, 1989
Summary
Caffeine activates cardiac sarcoplasmic reticulum Ca2+-release channels at the single-channel level. This activation increases channel open event frequency and duration, impacting cardiac muscle function.
Area of Science:
- Cardiology
- Molecular Physiology
- Pharmacology
Background:
- Caffeine is known to influence cardiac muscle excitation-contraction coupling.
- This effect is hypothesized to involve the activation of the sarcoplasmic reticulum (SR) Ca2+-release channel.
Purpose of the Study:
- To investigate the effect of caffeine on the cardiac sarcoplasmic reticulum Ca2+-release channel at the single-channel level.
- To elucidate the mechanism by which caffeine modulates channel activity.
Main Methods:
- Incorporation of canine cardiac SR vesicles into planar lipid bilayers.
- Electrophysiological recordings to analyze single channel activity.
- Kinetic analysis of channel gating properties under various conditions.
Main Results:
- Caffeine (millimolar concentrations) activated cardiac Ca2+-release channels, exhibiting a unitary conductance of 77 pS (in 50 mM Ca2+ trans).
- The caffeine-activated channel showed moderate voltage sensitivity, potentiation by ATP, and inhibition by Mg2+ and ruthenium red.
- At low Ca2+ concentrations, caffeine increased both the frequency and duration of channel open events.
Conclusions:
- Caffeine directly activates the cardiac sarcoplasmic reticulum Ca2+-release channel at the single-channel level.
- Caffeine modulates channel activity by altering open event kinetics, contributing to its effects on cardiac excitation-contraction coupling.