Effects of regional ischemia on the ryanodine-sensitive Ca2+ release channel of canine cardiac sarcoplasmic reticulum.
In mammalian myocardium, muscle contraction is regulated by the rapid release of Ca2+ ions through ryanodine-sensitive Ca2+ release channels present in the intracellular membrane compartment, sarcoplasmic reticulum (SR). In this study, the effects of regional ischemia on intrinsic SR Ca2+ release channel function were determined by studying the Ca2+ transport and release, and [3H]ryanodine binding properties of whole muscle homogenates and SR-enriched membrane fractions from normal and ischemic myocardium. Measurement of oxalate-supported 45Ca(2+)-uptake rates before and after pretreatment with 1 mM ryanodine, indicated that the SR Ca2+ release channel retained its ability to be effectively closed by the channel-specific probe ryanodine after 15 and 60 min of ischemia. 45Ca2+ efflux from, and high-affinity [3H]ryanodine binding to SR-enriched vesicle fractions indicated retention of regulation of Ca2+ release channel activity by Ca2+, Mg2+ and adenine nucleotide in 15 and 60 min ischemic samples. Further, sodium dodecylsulfate polyacrylamide gel and immunoblot analysis revealed no proteolytic degradation of the M(r) 565,000 SR Ca2+ release channel polypeptide after 15 and 60 min of ischemia. These results suggested a minimal, if any, loss of intrinsic SR Ca2+ release channel function in ischemic hearts.
Darling
E M
EM
Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill 27599-7260.
Lai
F A
FA
Meissner
G
G
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism*; D004285:Dogs; D009119:Muscle Contraction / Q000187:drug effects; D017202:Myocardial Ischemia / Q000378:metabolism*; D012433:Ryanodine / Q000494:pharmacology*; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*
D015220:Calcium Channels; D012433:Ryanodine; D002118:Calcium