Measurement of free Ca2+ in sarcoplasmic reticulum in perfused rabbit heart loaded with 1,2-bis(2-amino-5,6-difluorophenoxy)ethane-N,N,N',N'-tetraacetic acid by F-19 NMR
Measurement of free Ca2+ in sarcoplasmic reticulum in perfused rabbit heart loaded with 1,2-bis(2-amino-5,6-difluorophenoxy)ethane-N,N,N',N'-tetraacetic acid by F-19 NMR
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DOI：
10.1074/jbc.271.13.7398
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发表时间：
1996-03-29
影响因子：
4.8
通讯作者：
Murphy, E
中科院分区：
文献类型：
--
作者：
Chen, W;Steenbergen, C;Murphy, E
使用 F-19 NMR 在负载乙酰氧基甲酯的 Langendorff 灌注兔心脏中测量肌浆网中的游离钙离子浓度 ([Ca2+](SR)) 并评估其与细胞质游离钙和细胞能量状态变化的关系以及 SR 钙池的异质性。 1,2-双(2-氨基-5,6-二氟苯氧基)乙烷-N,N,N',N'-四乙酸。我们报告跳动心脏中的基线时间平均 [Ca2+](SR) 值为 1.5 mM (n = 13)，与舒张期测量的值相似。我们进一步报道，[Ca2+](SR) 在收缩期开始时下降了约 30%，并且没有证据表明收缩周期期间 [Ca2+](SR) 存在空间异质性。然而，对 SR 钙通道释放激活剂（咖啡因）和 SR 钙 ATP 酶抑制剂（环吡嗪酸）似乎存在异质反应，这与表明存在 SR 亚群的研究一致。通过用 30 mM 细胞外 KCl 去极化细胞来提高胞质游离钙，导致 [Ca2+](SR) 增加；然而，钙梯度没有改变。降低细胞磷酸化电位会减少 SR Ca2+-ATPase 可用的自由能，导致 SR 上的钙梯度下降，但这种梯度下降主要是由于胞质游离钙的增加，而不是 SR 钙的净释放。
Measurements of free calcium ion concentration in the sarcoplasmic reticulum ([Ca2+](SR)) and an evaluation of its relationship to changes in cytosolic free calcium and energy state of the cell, as well as heterogeneity of the SR calcium pool, were performed using F-19 NMR in Langendorff perfused rabbit hearts loaded with acetoxymethyl ester of 1,2-bis(2-amino-5,6-difiuorophenoxy)ethane-N,N,N',N'-tetraacetic acid. We report a base-line time-average [Ca2+](SR) value of 1.5 mM (n = 13) in the beating heart, similar to the value measured at diastole. We further report that [Ca2+](SR) decreases by similar to 30% at the start of systole and that there is no evidence of spacial heterogeneity in [Ca2+](SR) during the contraction cycle. However, there appears to be a heterogeneous response to SR calcium channel release activator (caffeine) and SR calcium-ATPase inhibitor (cyclopiazonic acid), consistent with studies suggesting that there are subpopulations of SR. Raising cytosolic free calcium by depolarizing the cell with 30 mM extracellular KCl, resulted in an increase in [Ca2+](SR); however, the calcium gradient was unchanged. Lowering cell phosphorylation potential, which would reduce the free energy available for the SR Ca2+-ATPase, leads to a decrease in the calcium gradient across the SR, but this reduced gradient was primarily due to an increase in cytosolic free calcium and not a net release of SR calcium.