Nitric oxide-induced hyperpolarization stimulates low-conductance Na+ channel of rat CCD.
Nitric oxide-induced hyperpolarization stimulates low-conductance Na+ channel of rat CCD.
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一氧化氮诱导的超极化刺激大鼠 CCD 的低电导 Na 通道。
DOI：
10.1152/ajprenal.1997.272.4.f498
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发表时间：
1997
期刊：
影响因子：
--
通讯作者：
Wang,W
中科院分区：
文献类型：
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作者：
Lu,M;Giebisch,G;Wang,W
我们在裂开的皮质集合管 (CCD) 中使用膜片钳技术来研究一氧化氮 (NO) 对可被 1 µM 阿米洛利阻断的低电导 (6-pS) Na+ 通道的影响。我们证实，低 Na+ 饮食的大鼠 CCD 中 Na+ 通道的数量显着增加 (17)。使用 100 microM N(G)-硝基-L-精氨酸甲酯 (L-NAME)（一种阻断内源性 NO 合酶的药物）可将 NPo [通道数 (N) 与开放概率 (Po) 的乘积] 降低至对照值的 45%。 L-NAME 的作用是特异的，因为添加不抑制 NO 合酶的 D-NAME 不会改变 Na+ 通道的活性。实验进一步证实了 L-NAME 的作用是抑制 NO 合酶，其中添加外源 NO 供体（10 µM S-亚硝基-N-乙酰青霉胺或硝普钠 (SNP)）可恢复被 L-NAME 阻断的 Na+ 通道活性。 NO 的作用涉及鸟苷 3',5'-环单磷酸 (cGMP) 依赖性途径，因为 100 microM 8-溴-cGMP (8-BrcGMP) 模拟 SNAP 对 K+ 通道的作用。然而，100 microM 8-BrcGMP 不会改变由内而外斑块中 Na+ 通道的活性，表明存在间接作用。由于超极化可激活 Na+ 通道 (19)，而 NO 会刺激基底外侧 K+ 通道 (16)，因此我们测试了超极化是否介导了 NO 的作用。在穿孔全细胞记录中，添加 L-NAME 使细胞膜从 -73 mV 去极化至 51 mV，并且应用 10 microM SNP 将细胞膜复极化至 -68 mV。此外，L-NAME 诱导的 NPo 减少可通过膜片膜 25 mV 超极化有效恢复，并且添加 2 mM Ba2+ 也消除了 L-NAME 的作用。我们得出结论，NO 对 Na+ 通道的刺激作用是由 NO 诱导的基底外侧 K+ 电导增加介导的间接作用。
We used the patch-clamp technique in the split-open cortical collecting duct (CCD) to investigate the effect of nitric oxide (NO) on the low-conductance (6-pS) Na+ channel that can be blocked by 1 microM amiloride. We confirmed that the number of Na+ channels increased significantly in CCDs of rats on a low-Na+ diet (17). Application of 100 microM N(G)-nitro-L-arginine methyl ester (L-NAME), an agent that blocks endogenous NO synthase, reduced NPo [the product of channel number (N) and open probability (Po)] to 45% of the control value. The effect of L-NAME was specific, since addition of D-NAME, which does not inhibit NO synthase, did not change the activity of the Na+ channel. That the effect of L-NAME results from inhibition of NO synthase is further confirmed by experiments in which addition of an exogenous NO donor, either 10 microM S-nitroso-N-acetyl penicillamine or sodium nitroprusside (SNP), restored the Na+ channel activity when it had been blocked by L-NAME. The action of NO involves a guanosine 3',5'-cyclic monophosphate (cGMP)-dependent pathway, since 100 microM 8-bromo-cGMP (8-BrcGMP) mimicked the effect of SNAP on K+ channels. However, 100 microM 8-BrcGMP did not alter the activity of Na+ channels in inside-out patches, suggesting an indirect action. Because the Na+ channel is activated by hyperpolarization (19) and NO stimulates basolateral K+ channels (16), we tested whether hyperpolarization mediated the effect of NO. In perforated whole cell recordings, addition of L-NAME depolarized the cell membrane from -73 to 51 mV, and application of 10 microM SNP repolarized the membrane to -68 mV. Furthermore, the L-NAME-induced decrease in NPo was effectively restored by 25 mV hyperpolarization of the patch membranes, and addition of 2 mM Ba2+ also abolished the effect of L-NAME. We concluded that the stimulatory effect of NO on the Na+ channel is an indirect effect mediated by a NO-induced increase of basolateral K+ conductance.