Putative ryanodine receptors in the sarcolemma of ventricular myocytes.
The activity of caffeine-activated large conductance channels was recorded in whole-cell, patch-clamped, isolated ventricular myocytes from rabbit heart. The channels were permeable to monovalent and divalent cations and had a unitary monovalent cation conductance of 300-400 pS. Extracellular ruthenium red reduced the unitary conductance of the caffeine-activated channel in a concentration- and voltage-dependent manner. Ryanodine locked the caffeine-activated channels into a subconductance state. Elevating intracellular Ca2+ by photolysis of "caged calcium" increased the number of channel openings. The properties of this caffeine-activated channel were remarkably similar to those of cardiac ryanodine receptors (RyR) and support the novel finding that these channels may also be found on the sarcolemmal membrane.
Kondo
R P
RP
Division of Cardiology, UCLA School of Medicine, Los Angeles, CA 90095-1679, USA.
Weiss
J N
JN
Goldhaber
J I
JI
D000085:Acetates / Q000494:pharmacology; D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D002478:Cells, Cultured; D002614:Chelating Agents / Q000494:pharmacology; D003593:Cytoplasm / Q000378:metabolism; D005029:Ethylenediamines / Q000494:pharmacology; D006352:Heart Ventricles / Q000166:cytology / Q000378:metabolism*; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism; D008536:Meglumine / Q000378:metabolism / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D011817:Rabbits; D012430:Ruthenium Red / Q000494:pharmacology; D012433:Ryanodine / Q000494:pharmacology; D019837:Ryanodine Receptor Calcium Release Channel / Q000187:drug effects / Q000378:metabolism*; D012508:Sarcolemma / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism; D013379:Substrate Specificity
D000085:Acetates; D002614:Chelating Agents; D005029:Ethylenediamines; D007473:Ion Channels; D019837:Ryanodine Receptor Calcium Release Channel; D012430:Ruthenium Red; D012433:Ryanodine; C057014:DM-nitrophen; D002110:Caffeine; D008536:Meglumine; D012964:Sodium; D002118:Calcium