Meissner G
J Biol Chem. 1984 Feb 25;259(4):2365-74.
Rabbit skeletal muscle sarcoplasmic reticulum was fractionated into a "Ca2+-release" and "control" fraction by differential and sucrose gradient centrifugation. External Ca2+ (2-20 microM) caused the release of 40 nmol of 45Ca2+/mg of protein/s from Ca2+-release vesicles passively loaded at pH 6.8 with an internal half-saturation Ca2+ concentration of 10-20 mM. Ca2+-induced Ca2+ release had an approximate pK value of 6.6 and was half-maximally inhibited at an external Ca2+ concentration of 2 X 10(-4) M and Mg2+ concentration of 7 X 10(-5) M. 45Ca2+ efflux from control vesicles was slightly inhibited at external Ca2+ concentrations that stimulated the rapid release of Ca2+ from Ca2+-release vesicles. Adenine, adenosine, and derived nucleotides caused stimulation of Ca2+-induced Ca2+ release in media containing a "physiological" free Mg2+ concentration of 0.6 mM. At a concentration of 1 mM, the order of effectiveness was AMP-PCP greater than cAMP approximately AMP approximately ADP greater than adenine greater than adenosine. Other nucleoside triphosphates and caffeine were minimally effective in increasing 45Ca2+ efflux from passively loaded Ca2+-release vesicles. La3+, ruthenium red, and procaine inhibited Ca2+-induced Ca2+ release. Ca2+ flux studies with actively loaded vesicles also indicated that a subpopulation of sarcoplasmic reticulum vesicles contains a Ca2+ permeation system that is activated by adenine nucleotides.
通过差速离心和蔗糖梯度离心，将兔骨骼肌肌浆网分离为“钙释放”组分和“对照”组分。外部钙离子（2 - 20微摩尔）导致从在pH 6.8下被动加载、内部半饱和钙离子浓度为10 - 20毫摩尔的钙释放囊泡中释放出40纳摩尔的45钙离子/毫克蛋白质/秒。钙诱导的钙释放的近似pK值为6.6，在外部钙离子浓度为2×10⁻⁴摩尔/升和镁离子浓度为7×10⁻⁵摩尔/升时被半数抑制。在刺激钙从钙释放囊泡快速释放的外部钙离子浓度下，对照囊泡的45钙离子外流略有抑制。腺嘌呤、腺苷及衍生核苷酸在含有“生理”游离镁离子浓度0.6毫摩尔的培养基中刺激钙诱导的钙释放。在1毫摩尔浓度下，效力顺序为：AMP - PCP＞环磷酸腺苷（cAMP）≈AMP≈二磷酸腺苷（ADP）＞腺嘌呤＞腺苷。其他核苷三磷酸和咖啡因在增加被动加载的钙释放囊泡的45钙离子外流方面效果甚微。镧离子（La³⁺）、钌红和普鲁卡因抑制钙诱导的钙释放。对主动加载囊泡的钙通量研究还表明，肌浆网囊泡的一个亚群含有一个被腺嘌呤核苷酸激活的钙离子渗透系统。
