Nitric oxide inhibits L-type Ca2+ current in glomus cells of the rabbit carotid body via a cGMP-independent mechanism.
Nitric oxide inhibits L-type Ca2+ current in glomus cells of the rabbit carotid body via a cGMP-independent mechanism.
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DOI：
10.1152/jn.1999.81.4.1449
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发表时间：
1999-04
影响因子：
2.5
通讯作者：
B. A. Summers;J. L. Overholt;N. Prabhakar
中科院分区：
文献类型：
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作者：
B. A. Summers;J. L. Overholt;N. Prabhakar
以往的研究表明，一氧化氮(NO)抑制颈动脉体感活动。为了开始了解NO在颈动脉体内作用的细胞机制，我们监测了NO供体对兔颈动脉体球细胞宏观钙电流的影响。实验采用膜片钳技术的全细胞构型，对新鲜分离的成年兔颈动脉球体细胞进行了实验。NO供体硝普钠(SNP；600微米，n=7)和精胺一氧化氮(SNO，100微米，n=7)以电压非依赖性的方式抑制血管球体细胞的钙电流。NO供者的这些效应起效迅速，并在1到2分钟内达到高峰。相反，SNP(600微米，n=6)对外向K+电流无影响，表明SNP的抑制作用不是一种非特异性膜效应。NO清除剂2-(4-羧基苯基)-4，4，5-四甲基咪唑啉-1-氧基-3-氧化物(Cxxy-PTIO；500 mM)可阻止SNP对钙电流的抑制(n=7)，而超氧化物歧化酶(SOD；2,000 U/ml，n=4)和还原剂亚硫酸钠(SHS；1 mM，n=7)均不能阻止SNP对钙电流的抑制。然而，SNP对钙电流的抑制在SOD或SHS存在时是可逆的。这些结果表明，NO本身以一种可逆的方式抑制钙电流，随后过氧亚硝酸盐的形成导致不可逆的抑制。SNP对钙电流的抑制作用不受30微米LY 83,583(n=7)的影响，也不能被600微米8-溴鸟苷3‘：5’-环一磷酸(8-Br-cGMP；n=6)所模拟，提示NO对钙电流的作用部分是通过cGMP非依赖性机制实现的。N-乙基马来酰亚胺(NEM；2.5 mM，n=6)可阻断SNP对钙电流的抑制作用，表明SNP通过修饰钙通道蛋白上的巯基发挥作用。去甲肾上腺素(NE；10微米)进一步抑制NEM(n=7)的钙电流，表明NEM不能非特异性地消除钙电流的调制。L型钙通道阻断剂尼索地平(2微米，n=6)可阻断硝普钠对钙电流的抑制作用，而N-型钙通道阻滞剂欧米茄毒素GVIA(1微米，n=9)不能阻断硝普钠对钙电流的抑制作用。这些结果表明，NO抑制成年兔肾小球细胞的L钙通道，部分是由于钙通道蛋白的修饰。这种抑制可能为NO传出抑制颈动脉体电活动提供了一种可能的机制。
Previous studies have shown that nitric oxide (NO) inhibits carotid body sensory activity. To begin to understand the cellular mechanisms associated with the actions of NO in the carotid body, we monitored the effects of NO donors on the macroscopic Ca2+ current in glomus cells isolated from rabbit carotid bodies. Experiments were performed on freshly dissociated glomus cells from adult rabbit carotid bodies using the whole cell configuration of the patch-clamp technique. The NO donors sodium nitroprusside (SNP; 600 microM, n = 7) and spermine nitric oxide (SNO; 100 microM, n = 7) inhibited the Ca2+ current in glomus cells in a voltage-independent manner. These effects of NO donors were rapid in onset and peaked within 1 or 2 min. In contrast, the outward K+ current was unaffected by SNP (600 microM, n = 6), indicating that the inhibition by SNP was not a nonspecific membrane effect. 2-(4-carboxyphenyl)-4,4,5, 5-tetramethyl-imidazoline-1-oxyl-3-oxide (carboxy-PTIO; 500 microM), an NO scavenger, prevented inhibition of the Ca2+ current by SNP (n = 7), whereas neither superoxide dismutase (SOD; 2,000 U/ml, n = 4), a superoxide scavenger, nor sodium hydrosulfite (SHS; 1 mM, n = 7), a reducing agent, prevented inhibition of the Ca2+ current by SNP. However, SNP inhibition of the Ca2+ current was reversible in the presence of either SOD or SHS. These results suggest that NO itself inhibits Ca2+ current in a reversible manner and that subsequent formation of peroxynitrites results in irreversible inhibition. SNP inhibition of the Ca2+ current was not affected by 30 microM LY 83, 583 (n = 7) nor was it mimicked by 600 microM 8-bromoguanosine 3':5'-cyclic monophosphate (8-Br-cGMP; n = 6), suggesting that the effects of NO on the Ca2+ current are mediated, in part, via a cGMP-independent mechanism. N-ethylmaleimide (NEM; 2.5 mM, n = 6) prevented the inhibition of the Ca2+ current by SNP, indicating that SNP is acting via a modification of sulfhydryl groups on Ca2+ channel proteins. Norepinephrine (NE; 10 microM) further inhibited the Ca2+ current in the presence of NEM (n = 7), implying that NEM did not nonspecifically eliminate Ca2+ current modulation. Nisoldipine, an L-type Ca2+ channel blocker (2 microM, n = 6), prevented the inhibition of Ca2+ current by SNP, whereas omega-conotoxin GVIA, an N-type Ca2+ channel blocker (1 microM, n = 9), did not prevent the inhibition of Ca2+ current by SNP. These results demonstrate that NO inhibits L-type Ca2+ channels in adult rabbit glomus cells, in part, due to a modification of calcium channel proteins. The inhibition might provide one plausible mechanism for efferent inhibition of carotid body activity by NO.