Role of nitric oxide in the regulation of airway iontransport

越来越多的证据表明，一氧化氮(NO)是一种由一氧化氮合酶(NOS)产生的氨基酸L-精氨酸产生的多用途信使分子，在多种气道功能中发挥作用，包括血管和气道平滑肌张力、宿主防御和肺神经传递。在本研究中，我们研究了NO在体外调节呼吸道上皮细胞运动功能和体内跨上皮电位差(PD)中的作用。神经激动素A(NKA)和P物质(SP)呈浓度依赖性地增加培养的犬气管上皮细胞短路电流，这种作用可被去苯胺羧酸盐所拮抗，但不能被阿米洛利所阻断。NKA和SP也能增加气管跨上皮PD。预先孵育细胞或气管灌流N-硝基-L-精氨酸甲酯(L-NAME，1 mM)可减弱NKA和SP引起的短路电流和阿米洛利敏感性PD的增加，使量效曲线右移，而NG-硝基-D-精氨酸(D-NAME，1 mM)不能。L-NAME的抑制作用可被L精氨酸(10 MM)逆转，但不能被D-精氨酸(10 MM)逆转。NO的释放是通过使用该分子的特定电流传感器实时测量灌流液中的NO浓度([NO])来确定的。NKA和SP呈剂量依赖性升高[NO]。因此，速激肽在体外增加短路电流，在体内增加阿米洛利敏感的PD，这可能反映了氯从气管粘膜下层向呼吸腔的移动，这一过程可能与上皮细胞产生的NO有关。

There is increasing evidence that nitric oxide (NO), a multipurpose messenger molecule generated from the amino acid L-arginine by nitric oxide synthase (NOS), plays a role in a variety of airway functions including vascular and airway smooth muscle tone, host defense, and pulmonary neurotransmission. In the present study, we investigated the role of NO in the regulation of airway epithelial ion tmsport function in vitro and transepithelial potential difference (PD) in vivo. Additoin of neurokinin A (NKA) and substance P (SP) increased short-circuit current of canine cultured tracheal epithelial cells in a concentratino-dependent manner, and these effects were abolished by dephenylamine carboxylate but not by amiloride. Tracheal transepithelial PD was also increased by NKA and SP.Preincubation of cells or tracheal perfusion with NG-nitro-L-arginine methylester (L-NAME,1 mM) attenuated the NKA- and SP-induced increase in short-circuit current and the amiloride-sensitive PD,causing a rightward displacement of the dose-response curves, whereas NG-nitro-D-arginine (D-NAME,1 mM) did not. The inhibitory effect of L-NAME was reversed by L-arginine (10 mM) but not by D-arginine (10 mM). The release of NO was determined by a real-time measurement of NO concentration ([NO]) in the perfusate using specific amperometric sensors for this molecule. NKA and SP increased [NO] in a dose-dependent manner. Therefore, tachykinins increase short-circuit current in vitro and amiloride-sensitive PD in vivo, which probably reflect Cl movement from the submucosa toward the respiratory lumen in tracheal mucosa and that NO generation by epithelial cells may be involved in this process.