Regulation of cardiac Ca2+ release channel (ryanodine receptor) by Ca2+, H+, Mg2+, and adenine nucleotides under normal and simulated ischemic conditions
Regulation of cardiac Ca2+ release channel (ryanodine receptor) by Ca2+, H+, Mg2+, and adenine nucleotides under normal and simulated ischemic conditions
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DOI：
10.1161/01.res.79.6.1100
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发表时间：
1996-12-01
影响因子：
20.1
通讯作者：
Meissner, G
中科院分区：
文献类型：
--
作者：
Xu, L;Mann, G;Meissner, G
心肌缺血时，pH（i）和[ATP]下降，而游离[Ca 2 +]和[Mg 2 +]上升。在[H-3]ryanodine结合和单通道测量中，使用分离的膜和纯化的通道制剂，研究了这些变化对心脏Ca 2+释放通道（ryanodine受体）活性的影响。在缺乏两个通道配体Mg ~（2+）和ATP的情况下，在pH7.4时，约4 μ mol/L胞浆Ca ~（2+）可使心脏Ca ~（2+）释放通道半最大激活，约9 mmol/L胞浆Ca ~（2+）可使其半最大抑制。Ca ~（2+）对通道活性的调节受Mg ~（2+）和ATP的调节。单通道活动更敏感的细胞溶质的pH值比SR内腔pH值的变化。内腔和/或细胞溶质的pH值从7.3减少到6.5和6.0导致单通道活动减少，而不改变单通道电导。[H-3]Ryanodine结合测量还表明，酸中毒会损害心脏Ca 2+释放通道的活性。Mg 2+和腺嘌呤核苷酸浓度调节的抑制程度和结合的Ca 2+依赖性。在5 mmol/L Mg 2+和5 mmol/L β，γ-亚甲基腺苷5 '-三磷酸（AMPPCP，一种不可水解的ATP类似物）存在下，游离[Ca 2 +]减半;最大[H-3]兰尼碱结合从pH 7.3时的1.9 μ mol/L增加到pH 6.5时的36 μ mol/L和pH 6.2时的89 μ mol/L。这些结果表明，离子和代谢的变化，可能会影响肌浆网Ca 2+释放通道的活性在缺血心肌包括改变Ca 2+的敏感性的通道，pH值下降，和损失的高能量腺嘌呤核苷酸池，导致增加抑制Mg 2+。
In myocardial ischemia, pH(i) and [ATP] fall, whereas the free [Ca2+] and [Mg2+] rise. The effects of these changes on cardiac Ca2+ release channel (ryanodine receptor) activity were investigated in [H-3]ryanodine binding and single-channel measurements, using isolated membrane and purified channel preparations. In the absence of the two channel ligands Mg2+ and ATP, cardiac Ca2+ release channels were half-maximally activated at pH 7.4 by approximate to 4 mu mol/L cytosolic Ca2+ and half-maximally inhibited by approximate to 9 mmol/L cytosolic Ca2+. Regulation of channel activity by Ca2+ was modulated by Mg2+ and ATP. Single-channel activities were more sensitive to a change of cytosolic pH than SR lumenal pH. Reduction in lumenal and/or cytosolic pH from 7.3 to 6.5 and 6.0 resulted in decreased single-channel activities without a change in single-channel conductance. [H-3]Ryanodine binding measurements also indicated that acidosis impairs cardiac Ca2+ release channel activity. Mg2+ and adenine nucleotide concentrations regulated the extent of inhibition and the Ca2+ dependence of binding. In the presence of 5 mmol/L Mg2+ and 5 mmol/L beta, gamma-methyleneadenosine 5'-triphosphate (AMPPCP, a nonhydrolyzable ATP analogue), the free [Ca2+] for half;maximal [H-3]ryanodine binding was increased from 1.9 mu mol/L at pH 7.3 to 36 mu mol/L at pH 6.5 and to 89 mu mol/L at pH 6.2. These results suggest that ionic and metabolic changes that might be expected to affect sarcoplasmic reticulum Ca2+ release channel activity in ischemic myocardium include an altered Ca2+ sensitivity of the channel, a fall in pH, and a loss of the high-energy adenine nucleotide pool, leading to an increased inhibition by Mg2+.