Single cardiac sarcoplasmic reticulum Ca2+-release channel: activation by caffeine.
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
E
E
Department of Biochemistry, University of North Carolina, Chapel Hill 27599-7260.
Meissner
G
G
D000818:Animals; D002110:Caffeine / Q000494:pharmacology*; D002118:Calcium / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D004285:Dogs; D004553:Electric Conductivity; D006321:Heart / Q000502:physiology*; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000502:physiology*
D015220:Calcium Channels; D002110:Caffeine; D002118:Calcium