Millimolar caffeine activated canine cardiac sarcoplasmic reticulum Ca2+-release channels by increasing the frequency and duration of open events.
Does caffeine activate the sarcoplasmic reticulum Ca2+-release channel in canine cardiac muscle?
Caffeine activates cardiac sarcoplasmic reticulum Ca2+-release channels by increasing the frequency and duration of open events, providing mechanistic insight into its effect on excitation-contraction coupling.
Caffeine is thought to affect excitation-contraction coupling in cardiac muscle by activating the sarcoplasmic reticulum (SR) Ca2+-release channel. The effect of caffeine at the single channel level was studied by incorporating canine cardiac SR vesicles into planar lipid bilayers. Cardiac Ca2+-release channels were activated in a steady-state manner by millimolar cis-caffeine and displayed a unitary conductance (77 pS in 50 mM Ca2+ trans) similar to that previously observed for the Ca2+-activated cardiac channel. The caffeine-activated channel was moderately sensitive to the voltage applied across the bilayer, was sensitive to further activation by ATP, and was inhibited by Mg2+ and ruthenium red. Kinetic analysis showed that at low Ca2+ concentration, caffeine activated the channel by increasing the frequency and the duration of open events.
Rousseau et al. (1989) studied Cardiac muscle excitation-contraction coupling. Caffeine was evaluated on Activation of cardiac Ca2+-release channels. Millimolar caffeine activated canine cardiac sarcoplasmic reticulum Ca2+-release channels by increasing the frequency and duration of open events.