Cooling and pH jump-induced calcium release from isolated cardiac sarcoplasmic reticulum.
Rapid-cooling contracture in cardiac muscle preparations is thought to be caused by the release of Ca2+ from the sarcoplasmic reticulum (SR), but the mechanism of this release is unknown. Cooling of isolated canine cardiac SR from 37 to 4 degrees C resulted in the net release of enough Ca2+ to account for rapid-cooling contracture. The release of Ca2+ on cooling appeared to be a relaxation between different steady-state levels of Ca2+ uptake. Cooling release of Ca2+ was also observed in the presence of ryanodine or ruthenium red to block the ryanodine-sensitive Ca2+ efflux pathway. In the presence of ryanodine, the extent and initial rate of rapid-cooling release were increased due to increased steady-state uptake of Ca2+ by the SR. The first-order rate constant of rapid-cooling Ca2+ release was unchanged by ryanodine or ruthenium red, suggesting that the rapid-cooling release does not occur through the ryanodine-sensitive pathway. The alkalinization on cooling was not the major cause of the Ca2+ release, as comparable Ca2+ release was observed with cooling and no alkalinization. However, alkalinization without cooling produced a rapid net Ca2+ release, which was also observed in the presence of ryanodine.
Feher
J J
JJ
Department of Physiology, Medical College of Virginia, Richmond 23298.
Rebeyka
I M
IM
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D003080:Cold Temperature; D004285:Dogs; D004533:Egtazic Acid / Q000494:pharmacology; D006706:Homeostasis; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D009206:Myocardium / Q000378:metabolism*; D012430:Ruthenium Red / Q000494:pharmacology; D012433:Ryanodine / Q000494:pharmacology; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*
D012430:Ruthenium Red; D012433:Ryanodine; D004533:Egtazic Acid; D002118:Calcium