Cell swelling and a nonselective cation channel regulated by internal Ca2+ and ATP in native reactive astrocytes from adult rat brain
Cell swelling and a nonselective cation channel regulated by internal Ca2+ and ATP in native reactive astrocytes from adult rat brain
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DOI：
10.1523/jneurosci.21-17-06512.2001
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发表时间：
2001-09-01
影响因子：
5.3
通讯作者：
Simard, JM
中科院分区：
文献类型：
--
作者：
Chen, MK;Simard, JM
缺氧缺血和ATP耗竭与胶质细胞肿胀和起泡有关，但参与这些影响的机制尚不完全清楚。我们检测了新鲜分离的天然反应性星形胶质细胞(NRAS)暴露于耗尽细胞ATP的NaN3后的形态和电生理反应。在这里，我们报告NaN3引起深刻和持续的去极化归因于激活一种新的35ps钙激活的，[ATP](I)敏感的非选择性阳离子(NCCA-ATP)通道，该通道存在于90%的离体膜片中。该通道对氯离子不渗透，对一价阳离子的渗透性几乎相等，相对于K+的渗透率接近P-Cs(+)/P-K(+)(1.06)接近P-Na(+)/P-K(+)(1.04)接近P-Rb(+)/P-K(+)(1.02)接近P-Li(+)/P-K(+)(0.96)，对钙、镁离子基本不透水(P-Ca(2+)/P-K(+)接近P-Mg(2+)/P-K(+)<；0.001)，细胞内镁离子(100M~1 mm)引起内向整流。通过将有机阳离子的相对渗透率与Renkin方程进行拟合，估算出孔半径为0.41 nm。与已报道的NCCA-ATP通道相比，该通道表现出明显不同的特性，包括对不同腺嘌呤核苷酸阻断的敏感性不同(对[ATP](I)的EC50为0.79um，不被AMP或ADP阻断)，以及被亚微摩尔[Ca]i激活。钙离子的表观解离常数与电压有关(在-40、-80和-120 mV时分别为0.12、0.31和1.5um)，Hill系数为1.5。[ATP]i耗竭导致的通道开放伴随着细胞膜的起泡，并且似乎先于细胞膜的起泡，表明该通道参与了阳离子通量，参与了细胞肿胀。结论：成年大鼠脑内NRAS表达一条35pS的NCCA-ATP通道，可能在脑肿胀的发病机制中起重要作用。
Hypoxia-ischemia and ATP depletion are associated with glial swelling and blebbing, but mechanisms involved in these effects remain incompletely characterized. We examined morphological and electrophysiological responses of freshly isolated native reactive astrocytes (NRAs) after exposure to NaN3, which depletes cellular ATP. Here we report that NaN3 caused profound and sustained depolarization attributable to activation of a novel 35 pS Ca2+-activated, [ATP](i)-sensitive nonselective cation (NCCa-ATP) channel, found in >90% of excised membrane patches. The channel was impermeable to Cl-, was nearly equally permeable to monovalent cations, with permeabilities relative to K+ being P-Cs(+)/P-K(+)(1.06) approximate to P-Na(+)/P-K(+)(1.04) approximate to P-Rb(+)/P-K(+)(1.02) approximate to P-Li(+)/P-K(+)(0.96), and was essentially impermeable to Ca2+ and Mg2+ (P-Ca(2+)/P-K(+) approximate to P-Mg(2+)/P-K(+) < 0.001), with intracellular Mg2+ (100 M to 1 mM) causing inward rectification. Pore radius, estimated by fitting relative permeabilities of organic cations to the Renkin equation, was 0.41 nm. This channel exhibited significantly different properties compared with previously reported NCCa-ATP channels, including different sensitivity to block by various adenine nucleotides (EC50 of 0.79 muM for [ATP](i), with no block by AMP or ADP), and activation by submicromolar [Ca] i. The apparent dissociation constant for Ca2+ was voltage dependent (0.12, 0.31, and 1.5 muM at -40, -80, and -120 mV, respectively), with a Hill coefficient of 1.5. Channel opening by [ATP] i depletion was accompanied by and appeared to precede blebbing of the cell membrane, suggesting participation of this channel in cation flux involved in cell swelling. We conclude that NRAs from adult rat brain express a 35 pS NCCa-ATP channel that may play an important role in the pathogenesis of brain swelling.