Single-channel properties of the sarcoplasmic reticulum calcium-release channel in slow- and fast-twitch muscles of Rhesus monkeys.
RyR1 is the main isoform of ryanodine receptor expressed in fast- and slow-twitch mammalian skeletal muscles although differences in Ca2+-release kinetics and properties have been reported. Single-channel measurements reveal that a large proportion (82%) of Ca2+-release channels measured in slow-twitch muscle preparations have properties similar to those of the Ca2+-release channels of fast-twitch preparations, i.e. the same conductance, an identical sensitivity to caffeine and a bell-shaped Ca2+ activation curve for pCa (-log10[Ca2+]) 7 to 3. A low proportion (18%) of Ca2+-release channels observed in preparations from slow-twitch muscles were characterized by a very high activity level. These channels were not inhibited at a millimolar concentration of Ca2+. Our data suggest that the different properties of Ca2+ release in slow- and fast-twitch muscles might not be related to intrinsic properties of the Ca2+-release channels of each type of muscle but rather to the co-expression of two isoforms of ryanodine receptor and the lower amount of Ca2+-release channels expressed in slow- than in fast-twitch muscles.
Bastide
B
B
Laboratoire de Plasticité Neuromusculaire, SN4, Université des Sciences et Technologies de Lille, F-59655 Villeneuve d'Ascq Cedex, France.
Mounier
Y
Y
D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D004594:Electrophysiology; D066298:In Vitro Techniques; D008253:Macaca mulatta; D018656:Muscle Fibers, Fast-Twitch / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D018657:Muscle Fibers, Slow-Twitch / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D019837:Ryanodine Receptor Calcium Release Channel / Q000187:drug effects / Q000502:physiology*; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*
D019837:Ryanodine Receptor Calcium Release Channel; D002110:Caffeine; D002118:Calcium