A sustained inward current activated at the diastolic potential range in rabbit sino‐atrial node cells.
A sustained inward current activated at the diastolic potential range in rabbit sino‐atrial node cells.
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兔窦房结细胞在舒张电位范围内激活持续的内向电流。
DOI：
10.1113/jphysiol.1995.sp020563
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发表时间：
1995
期刊：
影响因子：
--
通讯作者：
A. Noma
中科院分区：
文献类型：
--
作者：
Jiqing Guo;K. Ono;A. Noma
1.在阻断超极化激活电流和膜K+电导后，从-80 mV到-70 mV和-50 mV之间的去极化在窦房结细胞中诱导了持续电流。我们已经暂时指定了目前的第一。2. Ist被有机和无机Ca 2+通道阻断剂阻断，但对河豚毒素（30 μ M）不敏感。异丙肾上腺素增加Ist。3.通过将外部Ca 2+浓度（[Ca 2 +]o）从1.8降低至0.1 mM，Ist的峰值（约-50 mV）增加至149 +/-13%（n = 8，P < 0.01），与L-型Ca 2+电流的显著抑制相反。在0.1 mM [Ca 2 +]o溶液中，尼卡地平敏感性电流-电压关系显示峰值振幅约为-50 mV，反转电位为+37.4 +/-4.4 mV（n = 5）。异丙肾上腺素敏感成分也显示出约+30mV的逆转电位。4.在0.1 mM [Ca 2 +]o中将[Na+]o从140 mM降低至70 mM使Ist降低至53 +/-5%（n = 7，P < 0.01）。增加[Ca ~（2+）]o或[Mg ~（2+）]o可降低Ist的幅值。Mg 2+抑制的半最大浓度为2.2 mM。在1.8 mM [Ca 2 +]o时，Ist在-10 mV下夹持5 s失活，并在复极化至-80 mV后逐渐恢复，半衰期为1.36 +/-0.4 s（n = 6）。6.移行性窦房结细胞的Ist振幅最小。7. Ist的这些特征在定性上与通过将外部二价阳离子耗尽至微摩尔范围而诱导的L-型Ca 2+通道的单价阳离子电导的特征相当。我们的结论是，Ist是由L-型钙通道的一种新亚型产生的。
1. After blocking both the hyperpolarization‐activated current and the membrane K+ conductance, depolarizations from ‐80 mV to between ‐70 and ‐50 mV induced a sustained current in sino‐atrial node cells. We have tentatively designated this current Ist. 2. Ist was blocked by both organic and inorganic Ca2+ channel blockers, but was insensitive to tetrodotoxin (30 microM). Isoprenaline increased Ist. 3. The peak of Ist (at about ‐50 mV) was increased to 149 +/‐ 13% (n = 8, P < 0.01) by lowering the external Ca2+ concentration ([Ca2+]o) from 1.8 to 0.1 mM, in contrast to the marked depression of the L‐type Ca2+ current. In 0.1 mM [Ca2+]o solution, the nicardipine‐sensitive current‐voltage relation showed the peak amplitude at about ‐50 mV and a reversal potential of +37.4 +/‐ 4.4 mV (n = 5). The isoprenaline‐sensitive component also showed a reversal potential of about +30 mV. 4. Reducing [Na+]o from 140 to 70 mM in 0.1 mM [Ca2+]o decreased Ist to 53 +/‐ 5% (n = 7, P < 0.01). Increasing [Ca2+]o or [Mg2+]o decreased the amplitude of Ist. The half‐maximum concentration of Mg2+ inhibition was 2.2 mM. 5. At 1.8 mM [Ca2+]o, Ist was inactivated by clamping for 5s at ‐10 mV, and gradually recovered after repolarization to ‐80 mV with a half‐time of 1.36 +/‐ 0.4 s (n = 6). 6. The transitional sino‐atrial node cell had minimal amplitude of Ist. 7. These characteristics of Ist are qualitatively comparable to those of the monovalent cation conductance of the L‐type Ca2+ channel induced by depleting external divalent cations to the micromolar range. We conclude that Ist is generated by a novel subtype of L‐type Ca2+ channel.
DOI：
10.1073/pnas.86.5.1689
发表时间：
1989-03-01
影响因子：
11.1
作者：
LLINAS, R;SUGIMORI, M;CHERKSEY, B
通讯作者：
CHERKSEY, B
影响因子：
20.1
作者：
HIRANO, Y;MOSCUCCI, A;JANUARY, CT
通讯作者：
JANUARY, CT