Kim S Y, Marx K A, Wu C H
Department of Molecular Pharmacology and Biological Chemistry, Northwestern University Medical School, Chicago, IL 60611-3008, USA.
Naunyn Schmiedebergs Arch Pharmacol. 1995 May;351(5):542-54. doi: 10.1007/BF00171047.
The effects of ouabain, ATP, and vanadate on palytoxin induction of ion channels were examined with the aim of elucidating the role of Na,K-ATPase in palytoxin action. Palytoxin-induced membrane depolarization of crayfish giant axons and single channel currents of frog erythrocytes and mouse neuroblastoma N1E-115 cells were examined using the intracellular microelectrode and patch-clamp techniques. External application of palytoxin in nanomolar concentrations induced depolarization in the crayfish giant axons, and the depolarization was inhibited by pretreatment of the axon with ouabain (10 microM). Internally perfused axons were less sensitive to palytoxin unless ATP (6 mM) was added internally. In patch-clamp experiments, picomolar palytoxin in the patch electrode induced single channels in both cell-attached and inside-out patches of erythrocytes and neuroblastoma cells. The induced channels had a conductance of about 10 pS, reversed near 0 mV in physiological saline solution, and was permeable to Na+, K+, Cs+, and NH4+, but not to choline. Single channel activities induced by palytoxin were inhibited by ouabain (10 microM) and vanadate (1 mM), but promoted by ATP (1 mM). The modulating effects of ouabain, vanadate, and ATP on palytoxin action suggest that the Na,K-ATPase is involved in the induction of single channels by palytoxin. Palytoxin-induced and ouabain-inhibitable single channels were observed in planar lipid bilayer incorporated with purified Na,K-ATPase. The results indicate that an interaction between palytoxin and Na,K-ATPase leads to opening of a 10-pS ion channel. They further raise the possibility that a channel structure may exist in the sodium pump which is uncovered by the action of palytoxin.
为阐明钠钾 - ATP酶在海葵毒素作用中的角色，研究了哇巴因、ATP和钒酸盐对海葵毒素诱导离子通道的影响。使用细胞内微电极和膜片钳技术，检测了海葵毒素诱导的小龙虾巨轴突膜去极化以及青蛙红细胞和小鼠神经母细胞瘤N1E - 115细胞的单通道电流。以纳摩尔浓度的海葵毒素外部施加于小龙虾巨轴突会诱导去极化，而用哇巴因（10微摩尔）预处理轴突可抑制这种去极化。除非内部添加ATP（6毫摩尔），内部灌注的轴突对海葵毒素的敏感性较低。在膜片钳实验中，膜片电极中的皮摩尔级海葵毒素在红细胞和神经母细胞瘤细胞的细胞贴附式和内向外式膜片中诱导出单通道。诱导出的通道电导约为10皮安，在生理盐溶液中接近0毫伏时反转，对Na +、K +、Cs +和NH4 +通透，但对胆碱不通透。海葵毒素诱导的单通道活性受到哇巴因（10微摩尔）和钒酸盐（1毫摩尔）的抑制，但受到ATP（1毫摩尔）的促进。哇巴因、钒酸盐和ATP对海葵毒素作用的调节效应表明，钠钾 - ATP酶参与了海葵毒素诱导单通道的过程。在掺入纯化钠钾 - ATP酶的平面脂质双分子层中观察到了海葵毒素诱导且可被哇巴因抑制的单通道。结果表明，海葵毒素与钠钾 - ATP酶之间的相互作用导致了一个10皮安离子通道的开放。它们进一步提出了在钠泵中可能存在一种通道结构的可能性，这种通道结构会被海葵毒素的作用所揭示。
