碱性成纤维细胞生长因子对人晶体上皮细胞增殖及一氧化氮和诱导型一氧化氮合酶的影响

目的:探讨碱性成纤维细胞生长因子(bFGF)对人晶体上皮细胞内一氧化氮(NO)含量和诱导型一氧化氮合酶(iNOS)活性、基因及蛋白表达的影响。方法:以含10%胎牛血清(FBS)与100mg/L青霉素和100mg/L链霉素的DMEM培养液培养及传代人晶体上皮细胞。用0.001,0.01,0.1,1,10和100μg/L浓度的bFGF作用于晶体上皮细胞,用MTT法检测晶体上皮细胞的增殖情况;用Griess法测定NO含量;分别用RT-PCR方法及westernblot法检测iNOS基因及蛋白的表达。结果:①bFGF对细胞增殖的影响:与对照组比较,除100μg/L组外,其余浓度为0.001～10μg/L的bFGF对人晶体上皮细胞的增殖效应均大于对照组,其中0.01～10μg/L的bFGF对人晶体上皮细胞的增殖效应差异显著(P<0.05)。②bFGF对晶体细胞NO水平、NOS活性及iNOS的基因和蛋白表达的影响:对照组和0.001,0.01,0.1μg/LbFGF组NO水平较低,而在1μg/L和10μg/L的bFGF使人晶体上皮细胞的NO含量增高,0.1～10μg/L的bFGF使人晶体上皮细胞的NOS活性增高、使iNOS的基因和蛋白表达增强。结论:可以促进人晶体上皮细胞的增殖,使NO含量和iNOS的活性和蛋白表达增高。     

八肽缩胆囊素对脂多糖诱导血管内皮细胞诱生型一氧化氮合酶表达变化的抑制作用

目的探讨八肽缩胆囊素（CCK-8）对脂多糖（LPS）诱导血管内皮细胞诱生型一氧化氯合酶（iNOS）表达变化的影响。方法培养人脐静脉内皮细胞株ECV-304细胞。用0．01、0．1和1mg／L LPS处理2～24h，用生理盐水、10mol／LCCK-8和0．1mg／L LPS＋10^-8、10^-7、10^-8mol／L CCK-8处理16h；用比色法检测培养液中一氧化氮（NO）含量、细胞NOS活性，免疫细胞化学及蛋白质免疫印迹法检测iNOS蛋白表达。结果与生理盐水处理的对照组比较，LPS诱导培养液NO含量增多、细胞NOS活性增高、iNOS蛋白表达上调；CCK-8剂量依赣性抑制LPS的上述效应。而单独作用对iNOS蛋白表达、NOS活性和NO含量均无明显影响。结论CCK-8可以明显抑制LPS引起ECV-304细胞iNOS蛋白表达上调。减少NO生成。     

一氧化氮及一氧化氮合酶在哮喘大鼠气道高反应中的作用

目的：探讨一氧化氮及一氧化氮合酶(nitric oxide synthase，NOS)在哮喘大鼠气道炎症中的作用及激素对其活性的影响，以期为该病的预防、康复措施介入提供理论依据。方法：实验选用雄性豚鼠30只，按随机数字法将豚鼠分为3组：①哮喘组：用100g／L卵蛋白腹腔注射1mL致敏，2周后用10g／L卵蛋白超声雾化吸入致其哮喘发作。②激素组：诱喘同前，每次诱喘前腹腔内注射甲基强的松龙10mg／kg。③对照组：用生理盐水代替诱喘剂。每组分别测定其血浆和肺组织NO2^-／NO3^-水平、肺组织诱导型NOS(inducible nitric oxide synthase，iNOS)和原生型NOS(constitute nitric oxide synthase，cNOS)活性水平，并用组织化学染色法观察NOS在豚鼠哮喘模型肺组织中的分布。结果：3组豚鼠血浆NO2^-／NO3^-水平差异无显著性意义(P&;gt;0．05)，哮喘组肺组织中NO2^-／NO3^-和iNOS活性水平[(0．87&;#177;0．08)μmol／g，(56&;#177;14)nmol／g]明显高于对照组和激素组[(0．19&;#177;0．06)μmol／g，(12&;#177;6)mnol／g；(0．18&;#177;0．07)μmol／g，(12&;#177;5)nmol／g](P&;lt;0．01)。对照组肺组织化学方法显示的阳性产物呈蓝色沉淀，主要分布于各级支气管上皮细胞，哮喘组及激素组阳性产物变化不明显。哮喘组肺组织iNOS活性水平和肺组织NO2^-／NO3^-水平呈高度正相关(r=0．782．P&;lt;0．05)。结论：一氧化氮可引起气道高反应性而导致和(或)加重哮喘发病。用甲基强的松龙治疗哮喘可减轻气道炎症，使哮喘大鼠肺组织中iNOS表达降低。     

一氧化氮及一氧化氮合酶在哮喘大鼠气道高反应中的作用

目的:探讨一氧化氮及一氧化氮合酶(nitricoxidesynthase,NOS)在哮喘大鼠气道炎症中的作用及激素对其活性的影响,以期为该病的预防、康复措施介入提供理论依据。方法:实验选用雄性豚鼠30只,按随机数字法将豚鼠分为3组:①哮喘组:用100g/L卵蛋白腹腔注射1mL致敏,2周后用10g/L卵蛋白超声雾化吸入致其哮喘发作。②激素组:诱喘同前,每次诱喘前腹腔内注射甲基强的松龙10mg/kg。③对照组:用生理盐水代替诱喘剂。每组分别测定其血浆和肺组织NO2-/NO3-水平、肺组织诱导型NOS(induciblenitricoxidesynthase,iNOS)和原生型NOS(constitutenitricoxidesynthase,cNOS)活性水平,并用组织化学染色法观察NOS在豚鼠哮喘模型肺组织中的分布。结果:3组豚鼠血浆NO2-/NO3-水平差异无显著性意义(P>0.05),哮喘组肺组织中NO2-/NO3-和iNOS活性水平犤(0.87±0.08)μmol/g,(56±14)nmol/g犦明显高于对照组和激素组犤(0.19±0.06)μmol/g,(12±6)nmol/g;(0.18±0.07)μmol/g,(12±5)nmol/g犦(P<0.01)。对照组肺组织化学方法显示的阳性产物呈蓝色沉淀,主要分布于各级支气管上皮细胞,哮喘组及激素组阳性产物变化不明显。哮喘组肺组织i-NOS活性水平和肺组织NO2-/NO3-水平呈高度正相关(r=0.782,P<0.05)。结论:一氧化氮可引起气道高反应性而     

雾化吸入氯胺酮对哮喘大鼠肺组织一氧化氮及一氧化氮合酶的影响

目的通过建立大鼠支气管哮喘模型,观察不同浓度氯胺酮对哮喘大鼠肺组织iNOS活性及NO含量的影响。方法SD大鼠随机分成对照组(N组)、哮喘模型组(A组)、不同浓度氯胺酮预处理组(分别为K1组、K2组)和地塞米松组(D组),每组8只。A组大鼠用卵白蛋白辅以百日咳杆菌菌苗和氢氧化铝为佐剂注射致敏,2周后雾化吸入卵蛋白激发哮喘;氯胺酮处理组大鼠用同样方法致敏,但在激发前分别给予雾化吸入氯胺酮25 g/L(K1组)和50 g/L(K2组);D组在激发前给予雾化吸入0.01%地塞米松;N组用生理盐水替代卵蛋白进行注射和吸入。每组分别测定其肺组织NO2-/NO3-水平、肺组织诱导型NOS(iNOS)和原生型NOS(cNOS)活性水平,并用免疫组织化学法观察iNOS在大鼠哮喘模型肺组织中的分布。结果A组肺组织中NO2-/NO3-和iNOS水平升高,iNOS和肺组织NO2-/NO3-水平呈高度正相关;K1、K2组肺组织中NO2-/NO3-和iNOS水平低于A组(P<0.05);D组肺组织中NO2-/NO3-和iNOS水平亦低于A组(P<0.05)。结论25 g/L或50 g/L的氯胺酮雾化吸入可抑制哮喘大鼠肺组织iNOS活性,降低NO含量,减轻大鼠肺部炎症。     

血必净注射液对脓毒症肾脏损伤大鼠一氧化氮及其合酶作用的影响

目的 观察血必净注射液对脓毒症大鼠血浆及肾组织一氧化氮(NO)和一氧化氮合酶(iNOS)水平的影响,探讨血必净注射液的肾保护作用.方法 采用盲肠结扎穿孔术(CLP)制备脓毒症动物模型.健康雄性SD大鼠40只被随机分为正常对照组(n=8)、假手术组(n=8)、模型组(n=12)、血必净组(n=12).术后6 h留取标本,采用生化法测定血浆和肾组织NO含量及iNOS活性,光镜下观察肾脏形态学变化,透射电镜下观察肾脏超微结构变化.结果 模型组血浆和肾组织NO含量[血浆:(94.00±15.18)μmol/L,肾:(0.50±0.07)μmol/g]及iNOS活性[血浆:(6.19±0.82)U/ml,肾:(0.20±0.02)U/mg]均明显高于正常对照组[血浆NO:(52.52±13.61)μmol/L,iNOS(3.69±0.89)U/ml;肾NO:(0.32±0.07)μmol/g,iNOS:(0.16±0.01)U/mg]和假手术组[血浆NO:(51.49±19.00)μmol/L,iNOS:(3.26±1.00)U/ml;肾NO:(0.35±0.04)μmol/g,iNOS:(0.16±0.02)U/mg,P均<0.01];血必净组血浆和肾组织NO含量[血浆:(77.16±14.49)μmol/L,肾:(0.43±0.03)μmol/g]及iNOS活性[血浆:(4.48±0.93)U/ml,肾:(0.18±0.02)U/mg]均明显低于模型组(P<0.05或P<0.01);正常对照组与假手术组各项指标比较差异无统计学意义(P均>0.05).光镜及电镜下观察假手术组肾小球、肾小管结构基本正常;模型组肾脏损伤明显;血必净组肾脏损伤较模型组显著减轻.结论 NO和iNOS在脓毒症大鼠肾损伤发病过程中发挥了重要的作用,血必净注射液干预治疗可使血浆及肾组织中NO含量和iNOS活性下降,并可使肾脏损伤减轻,对肾脏具有保护作用.     

硝苯地平对自发性高血压大鼠血管内皮细胞的保护作用

背景：研究表明，硝苯地平能够改善血管内皮细胞功能，而对于其扩张血管的机制，目前仍在进一步的研究中。目的：观察硝苯地平控释剂对自发性高血压大鼠(SHR)一氧化氮(NO)及诱导性一氧化氮合酶(iNOS)的影响。设计：以实验动物为研究对象的观察对比研究。单位：一所医学院的动物实验中心。材料：本实验于2002—04／2002—05在山东大学医学院动物实验中心完成。实验动物为近交SHR大鼠21只，体质量(300&;#177;20)g，由山东大学医学院实验动物中心提供，清洁级。随机分为3组．即对照组．正常剂量组、低剂量组，每组7只。方法：对照组、正常剂量组和低剂量组分别灌胃生理盐水10mL／kg、硝苯地平控释剂(拜新同)溶液(0．3g／L)10mL／kg和3mL／kg，1次／d，连续15d。末次给药后摘眼球取血并取大鼠心、肺分别测定血清NO和iNOS的含量。主要观察指标：各组大鼠的NO含量、iNOS活性比较。结果：灌胃15d后，正常剂量组的NO含量与对照组、低剂量组比较，差异均有显著性意义(P&;lt;0．01)；正常剂量组心、肺组织块中iNOS活性降低，与对照组和低剂量组比较差异均有显著性意义(P&;lt;0．01，P&;lt;0．05)。结论：硝苯地平可在降低血压的同时，提高血清NO的含量，并且能对抗血压增高所造成的iNOS的活性增强(或二者互为因果)。     

一氧化氮在人骨髓间充质干细胞抑制淋巴细胞异基因增殖反应的初步研究

本研究探讨一氧化氮在骨髓间充质干细胞（MSC）抑制淋巴细胞增殖中的作用及机制。从人骨髓中分离培养MSC,预先接种在培养板上,建立混合淋巴细胞培养（MLC）体系,利用CCK-8法检测淋巴细胞增殖情况,并用Griess法检测培养体系NO的产生,real—timePCR检测淋巴细胞FOXP3mRNA表达水平。结果表明：MSC干预组淋巴细胞增殖活性下降,其OD值为0．49±0．03,NO含量明显升高为（21．05±1．14）μmol／L,淋巴细胞FOXP3mRNA表达水平为（1．56±0．34）％,而无MSC的MLC组NO含量为（3．30±0．36）μmol／L,FOXP3表达水平为（0．74±0．15）％,两组相比具有显著性差异。结论：MSC产生的NO上调淋巴细胞FOXP3mRNA的表达水平,从而抑制淋巴细胞增殖。     

碱性成纤维细胞因子和骨形成蛋白联合应用对骨髓干细胞的生物学效应

目的：观察不同剂量的碱性成纤维细胞因子和重组人骨形成蛋白2单独或交互作用对成人骨髓干细胞增殖、碱性磷酸酶和总蛋白含量合成的影响。方法：实验于1999-09／2002-07在解放军总医院口腔科实验室完成。取在解放军总医院体检的一名健康自愿者骨髓组织，将培养的骨髓干细胞暴露于不同浓度的碱性成纤维细胞生长因子或（和）重组人骨形成蛋白2中，①检测骨髓干细胞增殖能力，用酶联免疫检测仪490nm波长测光吸收值。②检测骨髓干细胞碱性磷酸酶活性，用酶联免疫检测仪410nm波长测光吸收值。③检测骨髓干细胞内蛋白质的含量，用酶联免疫检测仪595nm波长测光吸收值。结果：①骨髓干细胞增殖能力：浓度为10μg／L的碱性成纤维细胞生长因子与浓度为100μg／L重组人骨形成蛋白2联合使用时较对照组显著增加（0．28&;#177;0．03，0．14&;#177;0．02，P〈0．01）。②骨髓干细胞碱性磷酸酶活性：浓度为10μg／L的碱性成纤维细胞生长因子与浓度为100μg／L重组人骨形成蛋白2联合使用时较对照组显著增加（0．70&;#177;0．05，0．5l&;#177;0．02，P〈0．01）。③骨髓干细胞内蛋白质的含量：浓度为10μg／L的碱性成纤维细胞生长因子与浓度为100μg／L重组人骨形成蛋白2联合使用时较对照组显著增加（0．37&;#177;0．05，0．20&;#177;0．Ol，P〈0．01）。结论：碱性成纤维细胞生长因子可明显促进骨髓干细胞的增殖，但却抑制碱性磷酸酶和总蛋白含量；重组人骨形成蛋白2对骨髓干细胞的碱性磷酸酶活性、蛋白质含量均有明显的促进作用，且呈剂量依赖性，重组人骨形成蛋白2对骨髓干细胞的增殖也有一定促进作用；而二者交互联合应用对骨髓干细胞的增殖和分化有协同作用。     

白芍总苷对骨关节炎血清及关节液中一氧化氮及诱生型一氧化氮合酶的影响

目的 探讨白芍总苷（total ghcosides of paeony，TGP）对骨关节炎（OA）血清及关节液中一氧化氮（NO）及诱生型一氧化氮合酶（iNOS）的影响。方法 选择30例膝OA患者，予TGP治疗，于治疗前、治疗后1月和3月测定血清及关节液中NO及iNOS含量，比较其差异。结果 TGP治疗1月患者血清及关节液中NO及iNOS含量与治疗前相比无差异性（P〉0．05），治疗后3月患者血清及关节液中NO及iNOS含量与治疗前及治疗后1月相比均有显著差异性（P〈0．001）。结论 TGP可以降低OA患者血清及关节液中NO及iNOS的含量，是治疗OA的有效药物。     

Exhaled nitric oxide

We introduce the standard method of measurement of nitric oxide recommended by American thoracic society in 1999 and report the results of exhaled NO and nasal NO in patients with obstructive sleep apnea syndrome(OSAS). Our data showed lower exhaled NO output in the patients with OSAS than that of normal volunteers(NV) and that of patients with simple obesity(SO). On the other hand, nasal NO in the OSAS patients is higher than that of NV and that of SO patients. Also, there were significant relationships between apnea index and exhaled NO and between desaturation during sleep and nasal NO. These findings suggested that NO from lower and upper airway will be a non-invasive maker of sleep disordered breathing in future.     

Modulation of nitric oxide synthase by nitric oxide donor compounds in migraine

A controlled study was performed to assess the involvement of the nitric oxide pathway in migraine pathophysiology. Thirteen patients with migraine without aura and seven clinically healthy subjects (C) were selected. All of the migraine patients were studied both before, during an asymptomatic phase (t ₀), and 1 h after the administration of 5 mg isosorbide dinitrate, a nitric oxide donor able to induce an experimental migraine attack (t ₁). The nitric oxide levels were analyzed as nitrite accumulation in serum samples, in peripheral blood mononuclear cell extracts, and culture supernatants. Basal nitrite levels in serum samples and peripheral blood mononuclear cell culture supernatants of migraine patients and healthy subjects indicated that migraine patients possess an activated nitric oxide synthesis pathway (t ₀ vs. C F=8.16,P<0.01 and F=16.2,P<0.01, respectively). As expected, in the migraine patients treated with the nitric oxide donor, a marked increase of nitrite levels was observed in sera (t ₁ vs.t ₀ P<0.05,t=3.05). In contrast, during the nitric oxide donor-induced migraine attacks a statistically significant decrease of nitrite levels in peripheral blood mononuclear cell culture supernatants was observed (t ₁ vs.t ₀ P<0.01,t=−4.03), whereas a significant increase of nitrite in total cell extracts was detected (t ₁ vs.t ₀ P<0.001,t=−6.89). These preliminary data suggest that nitric oxide could be involved in the neurovascular modifications leading to a migraine attack.     

Exogenous nitric oxide regulates activity and synthesis of vascular endothelial nitric oxide synthase

Background Nitric oxide (NO) – a major signalling molecule of the vascular system – is constitutively produced in endothelial cells (EC) by the endothelial NO synthase (eNOS). Since a reduced NO synthesis is an early sign of endothelial dysfunction and NO delivering drugs are used to substitute the impaired endothelial NO production, we addressed the effect of exogenous NO on eNOS in human umbilical venous endothelial cell cultures. Materials and methods The synthetic NO donor DETA/NO (trade name, but in the following we refer to detNO), that releases NO in a strictly first order reaction with a half life of 20 h, was used in our experiments. Results Short‐term (20–30 min) detNO treatment of EC increases the Ser¹¹⁷⁷ phosphorylation of the constitutively expressed endothelial NOS and the production of endogenous NO generated by eNOS from [³H]arginine. The phosphorylation of eNOS is Akt‐dependent and completely reverted by the phosphatidylinositol‐3 kinase (PI‐3K) inhibitor LY294002. A prolonged continuous exposure of EC to detNO 150 µmol L^?1 over a period of 24–48 h causes a reversible cell cycle arrest at G₁‐phase associated with a larger cell volume and increased cell protein content (hypertrophic phenotype of EC). The eNOS protein and mRNA of the hypertrophic cells and the generation of endogenous NO are reduced but eNOS phosphorylation could still be elevated by stimulation with vascular endothelial growth factor. Conclusions Our data explain clinical studies describing a short‐term but not a long‐term benefit of NO treatment for patients with cardiovascular risk factors. The results could be a rational approach to develop a generation of NO donors accomplishing a retarded release from NO donors that mimic the low continuous pulsatile stress‐induced release of endogenous NO.     

大鼠小肠移植术后血清一氧化氮及小肠组织一氧化氮合酶和诱导型一氧化氮合酶活性的变化

目的:研究同种大鼠小肠移植后内源性一氧化氮、一氧化氮合酶(nitricoxidesynthase,NOS)及诱导型一氧化氮合酶(induciblenitricoxidesyn-thase,iNOS)的变化及一氧化氮与急性排斥反应的关系。方法:以大鼠小肠移植为研究对象,16只SD大鼠进行同系移植作为对照组,8只SD大鼠和8只Wistar大鼠进行同种移植作为实验组,两组移植后分别于第3,5,7天同时取血液及小肠组织,病理为常规苏木精-伊红染色观察,血清一氧化氮采用硝酸还原酶法测定,NOS和iNOS采用分光光度法测定。结果:在急性排斥反应发生的早期实验组血清一氧化氮水平与对照组比较显著升高(术后第3,5,7天t值分别为9.7900,9.0073,6.3159,P<0.01),小肠组织NOS及iNOS活性亦显著高于对照组(NOS术后第3,5,7天t值分别为5.9318,9.1237,3.0457,iNOS术后第3,5,7天t值分别为3.2008,5.4930,4.8170,P<0.01)。结论:大鼠小肠移植后NOS及iNOS变化与排斥反应相关,血清一氧化氮水平的检测可作为干预移植措施始动的指标之一。     

Intraoperative administration of nitric oxide

Despite its therapeutic efficacy in various clinical scenarios in the intensive care unit setting, there are limited reports regarding the intraoperative applications of nitric oxide (NO). The authors present 2 pediatric patients to whom inhaled NO was administered intraoperatively. In one patient, NO was used to treat hypoxemia that developed after the institution of one-lung ventilation during thoracoscopic resection of a bronchiectatic section of lung. In the second patient, NO was used to alleviate pulmonary hypertension and cardiovascular dysfunction with pulmonary artery cross-clamping for placement of a modified Blalock-Taussig shunt. The potential intraoperative applications and techniques for the intraoperative delivery of NO are presented.     

The role of nitric oxide synthase/nitric oxide in vascular smooth muscle control

Vascular compliance is dependent on endogenous and exogenous sources of nitric oxide (NO). In a discussion of therapeutics and NO derived via nitric oxide synthase (NOS) enzymes, it is necessary to examine the pathways of each drug to provide the clinical perfusionist with a greater understanding of the role of NOS/NO in vascular function. Endothelial-derived NO is a contributor in the vasoregulation of vascular smooth muscle. Therapeutics seek to mimic the vasodilatory effects of the endogenous NO. The therapeutics included in this review are nitroglycerin, nitroprusside, amyl nitrite, and inhalation of NO. L-Arginine supplementation provides additional substrate for the endogenous pathway that can augment NO production. NO is a small bioactive molecule involved in various biochemical pathways. Dysregulation of NO production can impair normal physiologic control of vascular compliance. Therefore, the purpose of this review is to provide the perfusionist with an understanding of the biochemical and pharmacological aspects of NOS/NO associated with vascular function.     

Inhaled nitric oxide down-regulates intrapulmonary nitric oxide production in lipopolysaccharide-induced acute lung injury

OBJECTIVE: To examine whether inhaled nitric oxide (NO) affected the intrapulmonary production of NO, reactive oxygen species, and nuclear factor-kappaB in a lipopolysaccharide (LPS)-induced model of acute lung injury. DESIGN: Prospective, randomized, laboratory study. SETTING: Experimental laboratory at a biomedical institute. SUBJECTS: Twenty male rabbits weighing 2.5-3.5 kg. INTERVENTIONS: Saline or LPS (5 mg/kg of body weight) was administered intravenously with or without NO inhalation (10 ppm) in each group of five rabbits. MEASUREMENTS AND MAIN RESULTS: LPS increased the lung leak index, the neutrophils and NO levels in bronchoalveolar lavage fluid, and NO levels produced by resting and stimulated alveolar macrophages. Inhaled NO decreased the lung leak index, the neutrophils and NO levels as measured by nitrite levels in the lavage fluid, and NO produced by the resting and stimulated alveolar macrophages. Inhaled NO also blocked the activities of reactive oxygen species and nuclear factor-kappaB binding to DNA in lavage cells and in alveolar macrophages. CONCLUSION: Inhaled NO attenuates LPS-induced acute lung injury, possibly by decreasing NO production in the lungs. The mechanism of reducing NO production resulting from inhaled NO may involve, in part, the activities of reactive oxygen species and/or nuclear factor-kappaB.     

Recovery from withdrawal of inhaled nitric oxide and kinetics of nitric oxide-induced inhibition of nitric oxide synthase activity in vitro

Objective: To examine the kinetics of successful nitric oxide (NO) withdrawal in vivo and in vitro.¶Design and setting: Prospective study in a university pediatric intensive care ward and research laboratory.¶Patients and materials: Nineteen patients with acute respiratory distress syndrome (ARDS) or persistent pulmonary hypertension of the newborn (PPHN). Primary porcine pulmonary artery cells in vitro.¶Interventions: NO inhalation and withdrawal in patients; exposure to NO donor sodium nitroprusside (SNP) and gaseous NO in vitro.¶Measurements and results: In patients: a slight, but significant, increase of oxygenation index (OI) from 4.57 ± 0.24 cmH₂O/torr (mean ± SEM) to 4.90 ± 0.26 cmH₂O/torr after withdrawal of NO (p < 0.001). Recovery of OI (4.43 ± 0.23 cmH₂O/torr) 30 min after weaning, a significant drop after 4 h (3.72 ± 0.17 cmH₂O/torr; p < 0.001), values restored after 12 h.¶In vitro: NO synthase (NOS) activity was significantly lower in SNP-incubated cells (20.0 ± 4.0 μm/min) than in control cells (37.6 ± 7.0 μm/min; p < 0.05). Thirty minutes after SNP withdrawal there was NOS activity of 35.8 ± 10.0 μm/min with a significant increase by 4 h (p < 0.05). No alteration of endothelial NOS (ENOS) mRNA expression by NO (Northern Blot).¶Conclusion: In patients there is a slight, but significant, reversible increase of OI after successful weaning from NO. In vitro, NO leads to a reversible decrease of ENOS activity on a post mRNA level, resembling clinical observations.