Membrane depolarization in PC-12 cells during hypoxia is regulated by an O2-sensitive K+ current.
Membrane depolarization in PC-12 cells during hypoxia is regulated by an O2-sensitive K+ current.
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缺氧期间 PC-12 细胞的膜去极化受到 O2 敏感 K 电流的调节。
DOI：
10.1152/ajpcell.1996.271.2.c658
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
Millhorn,DE
中科院分区：
文献类型：
--
作者：
Zhu,WH;Conforti,L;Czyzyk-Krzeska,MF;Millhorn,DE
研究了缺氧对大鼠嗜铬细胞瘤 (PC-12) 细胞中 K+ 电流 (IK)、静息膜电位和胞质游离 Ca2+ 的影响。进行全细胞电压钳和电流钳实验以分别测量 IK 和膜电位。使用 Ca(2+) 敏感荧光染料 fura 2 测量胞质游离 Ca2+ 水平。将去极化电压从 -90 mV 的保持电位阶跃至 +50 mV 会引发缓慢失活的四乙基氯化铵敏感且 Ca(2+) 不敏感的 IK，该 IK 会被降低的 O2 张力可逆地抑制。 PO2 的分级降低（从 150 至 0 mmHg）引起 O2 敏感 IK [IK(O2)] 的分级抑制，在 0 mmHg 时高达 46%。此外，缺氧诱导 19 mV 膜去极化和胞质游离 Ca2+ 增加两倍。在无 Ca(2+) 条件下，抑制 IK(O2) 诱导 8 mV 去极化，表明抑制 IK(O2) 是引发去极化的原因。 PO2 减少对电流-电压关系的影响表明，与电流钳实验中测量的去极化量相当，外向电流减少，并且反转电位移动 14 mV。 Ca(2+) 激活的 IK 和内向整流 IK 均不负责缺氧诱导的去极化。总之，PC-12 细胞表达 IK(O2)，抑制 IK(O2) 会导致膜去极化和细胞内 Ca2+ 增加，使 PC-12 克隆细胞系成为研究介导 O2 化学敏感性的分子和生物物理机制的有用模型。
The effects of hypoxia on K+ current (IK), resting membrane potential, and cytosolic free Ca2+ in rat pheochromocytoma (PC-12) cells were studied. Whole cell voltage- and current-clamp experiments were performed to measure IK and membrane potential, respectively. Cytosolic free Ca2+ level was measured using the Ca(2+)-sensitive fluorescent dye fura 2. Depolarizing voltage steps to +50 mV from a holding potential of -90 mV elicited a slowly inactivating, tetraethylammonium chloride-sensitive, and Ca(2+)-insensitive IK that was reversibly inhibited by reduced O2 tension. Graded reduction in PO2 (from 150 to 0 mmHg) induced a graded inhibition of O2-sensitive IK [IK(O2)] up to 46% at 0 mmHg. Moreover, hypoxia induced a 19-mV membrane depolarization and a twofold increase in cytosolic free Ca2+. In Ca(2+)-free condition, inhibition of IK(O2) induced an 8-mV depolarization, suggesting that inhibition of IK(O2) was responsible for initiating depolarization. The effect of reduced PO2 on the current-voltage relationship showed a reduction of outward current and a 14-mV shift in the reversal potential comparable with the amount of depolarization measured in current clamp experiments. Neither Ca(2+)-activated IK nor inwardly rectifying IK are responsible for the hypoxia-induced depolarization. In conclusion, PC-12 cells express an IK(O2), inhibition of which leads to membrane depolarization and increased intracellular Ca2+, making the PC-12 clonal cell line a useful model for studying the molecular and biophysical mechanisms that mediate O2 chemosensitivity.