高血压大鼠主动脉一氧化氮合成途径的变化

目的 观察高血压大鼠主动脉内膜，中膜和外膜一氧化氮合成途径的改变，并探讨其可能的病理生理意义。方法 Wistar大鼠缩窄腹主动脉复制高血压模型，动物随机分为对假手术组和高血压。取大鼠主动脉，分离血管内膜，中膜和外膜。分别测定其亚硝酸盐（NO2^-)生成量，一氧化氮合酶（NOS）活性及L－精氨酸（L－Arg)转运，免疫组化染色检测诱导型一氧化氮合酶（iNOS)的分布。结果 与假手术组相比，高血压大鼠血中一氧化氮代谢产物（NOx)高26．2％（P＜0．05）；主动脉NO2^-生成低65．8％（P＜0．01），中膜及外膜孵育液的NO2^-生成量分别高59．6％和123．6％（均P＜0．01）；主动脉内膜NOS活性低59．3％（P＜0．01），中膜和外膜NOS活性分别高62．6％和118．7％（均P＜0．01），血管内膜L－Arg转运率低62．5％（P＜0．01），中膜和外膜L－Arg转运率分别高53．7％和99．8％（均P＜0．01）。iNOS免疫组化染色显示，高血压大鼠血管中膜和外膜尤其是外膜iNOS阳性染色明显增强。结论 高血压大鼠血管管一氧化氮合成与代谢发生改变，血管内膜L－Arg/NOS/NO途径受抑，而中膜和外膜尤其是外膜的L－Arg/NOS/NO系统的活性增强，血管生成的NO增多。提示血管中膜和外膜源NO增多在高血压时可能具有一定的代偿作用。     

血管外膜源一氧化氮对内皮素—1诱导的血管平滑肌增殖的影响

目的 观察血管外膜生成的一氧化氮（NO）对内皮素－1（ET－1）诱导的血管平滑肌（VSM）增殖的影响，以探讨血管外膜源NO对血管结构重塑调节的意义。方法 取大鼠胸主动脉，去除内皮，分以下几组进行组织孵育10h：（1）完整外膜血管组；（2）单纯中膜组；（3）中膜与剥离的外膜共育组；（4）中膜与服L－N－硝基精氨酸（L-NNA)预处理的外膜共育组。每例胸主动脉剪为二段，分两个亚组：ET（10^-7mol/L)组和对照组。^3H-胸腺嘧啶（^3H-TdR)掺入法检测各组VSM的细胞增殖。另取大鼠腹主动脉外膜，用10^-8和10^-7mol/L ET-1刺激4h。Griess法测血管外膜生成的亚硝酸（NO2-)含量，^3H-L－精氨酸（^3H-L-Arg)标记的同位素法测定外膜一氧化氮合酶（NOS）活性。结果 （1）各ET亚组^3H-TdR掺入比相应对照组分别增加48．8％－71．9％。（2）在10^-7mol/L ET-1刺激下，完整外膜组及中膜＋外膜组的^3H-TdR掺入分别比单纯中膜组低21．3％和24．5％。中膜＋L－NNA预处理的外膜组^3H-TdR掺入分别比中膜＋外膜组及完整外膜组高30．8％和25．4％，而与单纯中膜组差异无显著性。（3）与对照组相比，10^-8和10^-7mol/L 的ET－1使外膜NOS活性分别增加124％和177％；使外膜生成的NO2－含量分别增加88％和225％。结论 实验结果表明：血管外膜生成的NO可抑制ET－1刺激的VSM的增殖，其抑制作用为ET－1激活的血管外膜NOS／NO途径所分导。提示血管外膜源NO可能参与心血管疾病过程中血管重塑的调节。     

人参二醇皂苷对失血性休克-内毒素二次打击大鼠肺组织一氧化氮含量的影响

目的探讨失血性休克复合内毒素二次打击大鼠肺组织一氧化氮（NO）含量的变化及人参二醇皂苷（PDS）对其影响。方法利用失血性休克对Wistar大鼠制造首次打击，给予地塞米松（Dex）或PDS预治疗，之后腹腔注入脂多糖（LPS）进行第二次打击，二次打击6h后处死大鼠，取肺脏组织进行一氧化氮合酶（NOS）、诱导型NOS（iNOS）活力和NO代谢产物NO2^-／NO3^-含量的测定。结果二次打击的大鼠肺脏组织NOS、iNOS活力水平及N02-／N03-均明显高于假手术对照组（P〈0．05），而经过Dex或PDS处理的大鼠肺脏组织NOS、iNOS活力水平及NO2^／NO3^-与二次打击大鼠相比均明显降低（P〈0．05）。结论失血-内毒素二次打击时，NO产生过多可能参与了急性肺损伤的发生，PDS可通过抑制NO的产生从而达到保护肺脏的作用。     

肿瘤坏死因子α诱导脑血管内皮细胞产生病理性一氧化氮的实验研究

目的探讨肿瘤坏死因子α（TNF—α）作用于脑血管内皮细胞产生病理性一氧化氮（NO）的机制。方法体外培养肿瘤坏死因子受体（TNFR1）基因敲除的小鼠脑血管内皮细胞（BVEC／RI）和野生型小鼠脑血管内皮细胞（BVEC）,分别给予5ng／ml TNF-α刺激24h后,应用PCR技术、Western blot方法、硝酸还原酶法,测定两种细胞的诱导型一氧化氮合酶（iNOS）基因mRNA和蛋白表达量以及所分泌的一氧化氮（NO）含量。结果①给予TNF—α刺激后,野生型BVEC的iNOS mRNA表达增加,BVEC／RI的iNOS mRNA表达未出现明显变化。②给予TNF—α刺激后,野生型BVEC的iNOS蛋白表达量（0．91±0．08）高于未给予TNF-α的BVEC（0．15±0．02）,差异有统计学意义,P〈0．05;BVEC／RI的iNOS蛋白表达量（0．21±0．06）与未给予TNF—α的BVEC／RI（0．30±0．05）相比,差异无统计学意义,P〉0．05。③给予TNF-α刺激后,野生型BVEC的NO含量[（58．6±2．6）μxmol／L]高于未给予TNF—α的BVEC[（18．1±4．3）μmol／L],差异有统计学意义,P〈0．05;BVEC／RI的NO含量[（21．2±3．5）μmol／L]与未给予TNF-α的BVEC／RI[（16．9±3．4）μmol／L]相比,差异无统计学意义,P〉0．05。结论TNF—α可能通过作用于脑血管内皮细胞TNFR1增加iNOS表达,从而增加病理性NO产生。     

高血压大鼠主动脉一氧化氮合成途径的变化

目的观察高血压大鼠主动脉内膜、中膜和外膜一氧化氮合成途径的改变,并探讨其可能的病理生理意义.方法 Wistar大鼠缩窄腹主动脉复制高血压模型,动物随机分为对假手术组和高血压组.取大鼠主动脉,分离血管内膜、中膜和外膜.分别测定其亚硝酸盐(NO2--)生成量、一氧化氮合酶(NOS)活性及L-精氨酸(L-Arg)转运,免疫组化染色检测诱导型一氧化氮合酶(iNOS)的分布.结果与假手术组相比,高血压大鼠血浆中一氧化氮代谢产物(NOx)高26.2%(P<0.05);主动脉NO2--生成低65.8%(P<0.01),中膜及外膜孵育液的NO2--生成量分别高59.6%和123.6%(均P<0.01);主动脉内膜NOS活性低59.3% (P<0.01),中膜和外膜NOS活性分别高62.6%和118.7%(均P<0.01);血管内膜L-Arg转运率低62.5%(P<0.01),中膜和外膜L-Arg转运率分别高53.7%和99.8%(均P<0.01).iNOS免疫组化染色显示,高血压大鼠血管中膜和外膜尤其是外膜iNOS阳性染色明显增强.结论高血压大鼠血管壁一氧化氮合成与代谢发生改变,血管内膜L-Arg/NOS/NO途径受抑,而中膜和外膜尤其是外膜的L-Arg/NOS/NO系统的活性增强,血管生成的NO增多.提示血管中膜和外膜源NO增多在高血压时可能具有一定的代偿作用.     

醛固酮促进心肌成纤维细胞增殖的实验研究

目的：研究醛固酮对培养心肌成纤维细胞增殖的影响。方法：培养新西兰白兔心肌成纤维细胞,将第三代心肌成纤维细胞分为醛固酮组（不同浓度）、醛固酮＋螺内酯组和对照组,心肌成纤维细胞的代谢活性与DNA合成分别用WST-1试剂和5′溴脱氧尿嘧啶核苷（BrdU）酶联免疫吸附试验（ELISA）进行测定。结果：与对照组比较,不同浓度醛固酮作用后,心肌成纤维细胞的WST-1与BrdU的OD值均增加,并呈浓度依赖性（P〈0．05～〈0．01）;丽螺内酯＋醛固酮组的WST-1与BrdU的OD值明显低于醛固酮组（P〈0．01）。结论：在体外,醛固酮能诱导心肌成纤维细胞增殖,而螺内酯抑制其作用。     

大鼠肠缺血后回肠组织内一氧化氮代谢的变化

目的：研究缺血及缺血再灌注后肠组织内NO代谢产物的变化。方法：建立大白鼠肠系膜上动脉阻断模型，采用荧光法测定回肠组织内NO2^-含量，结果：缺血后30min，肠组织NO2^-上升，2h达高峰，缺血再灌注组，在复灌30min,60min,120min,180min时NO2^-含量均明显高于单纯缺血组，缺血前腹腔给予iNOS抑制剂氨基胍（AG）可明显降低缺血及缺血再灌时肠组织NO2^-含量。结论：肠缺血及缺血再灌注后肠组织内NO2^-含量发生明显改变，iNOS抑制剂AG对缺血及缺血再灌所致iNOS活性增高有明显抑制作用。NO参与了肠缺血再灌注的损伤过程。     

640例高血压患者中原发性醛固酮增多症患病率及临床特点

目的　探讨高血压患者中原发性醛固酮增多症（PA）的患病率,并分析PA患者的临床特点。方法　选择就诊于东莞市中医院内科门诊高血压患者640例,于清晨9∶30～10∶30患者起床2小时后,取坐位5～15　min后采血测定血浆醛固酮（ALD）水平和肾素活性（PRA）,计算血浆醛固酮/血浆肾素活性比值（ARR）。ARR≥30且ALD水平≥15　ng／dL的患者接受开博通试验,服开博通后2小时血浆醛固酮水平抑制程度≤30%,则试验结果为阳性,诊断为原发性醛固酮增多症^［1］。进一步分型时,PA患者均进行肾上腺薄层增强CT检查,诊断为特发性醛固酮增多症（IHA）的患者加用盐皮质激素受体拮抗剂（螺内酯）治疗,诊断为醛固酮瘤（APA）患者予以在腹腔镜下行单侧肾上腺切除术。结果　640例患者中112例（17.5%）ARR≥30,其中87例（13.59%）ARR≥30且ALD水平≥15　ng／dL的患者接受开博通试验。服用开博通2　h后血ALD水平抑制≤30%者32例,确诊为PA（5%）,其中20例诊断为APA（3.125%）,另外12例（1.875%）诊断为IHA。诊断为IHA的患者加用螺内酯治疗,醛固酮瘤患者予以在腹腔镜下行单侧肾上腺切除术。结论　高血压人群中原发性醛固酮增多症的患病率较高,要重视高血压患者中原发性醛固酮增多症的筛查,原发性醛固酮增多症患者临床具有高血压、低血钾、高尿钾、高醛固酮、低肾素、高ARR的典型临床特点。     

洛伐他汀对醛固酮诱导鼠心肌成纤维细胞增殖及其 iNOS-NO 系统活性的调控作用

目的：探讨洛伐他汀对醛固酮诱导心肌成纤维细胞（ CFs）增殖及诱导型一氧化氮合酶-一氧化氮（ iN-OS-NO）系统活性的调控作用。方法用胰酶消化法分离、培养新生SD大鼠CFs,采用MTT比色法、硝酸还原酶法、分光光度法和半定量RT-PCR技术,观察不同浓度洛伐他汀对CFs增殖、NO含量、iNOS活性和iNOS mRNA表达的影响。结果洛伐他汀（1×10-8～1×10-5 mol/L）能剂量依赖性抑制醛固酮诱导CFs的增殖,升高CFs的NO含量、iNOS活性及增加iNOS mRNA的表达（P均＜0．05）,甲羟戊酸（1×10-3 mol/L）、法尼酯焦磷酸（5μmol/L）可完全逆转洛伐他汀的上调作用。洛伐他汀干预下醛固酮诱导CFs的NO生成量与iNOS活性、iNOS活性与iNOS mRNA表达均呈正相关（r分别为0．826、0．752,P均＜0．01）;CFs增殖数目与NO含量呈负相关（r＝-0．908,P＜0．01）。结论洛伐他汀可上调醛固酮诱导CFs的iNOS-NO系统活性,抑制CFs增殖,并呈剂量依赖性,其作用机制可能与甲羟戊酸途径调节有关。     

早期糖尿病肾病患者ACEI治疗后醛固酮逃逸现象及螺内酯干预的疗效研究

目的探讨早期糖尿病肾病患者长时间服用血管紧张素转化酶抑制剂（ACEI）后的醛固酮逃逸现象,及螺内酯干预醛固酮逃逸对糖尿病肾病患者的意义。方法将168例早期糖尿病肾病患者随机分为ACEI、ARB（血管紧张素Ⅱ受体拮抗剂）组,检测其长期服用依那普利和缬沙坦后血浆血管紧张素Ⅱ（AngH）、醛固酮（Ald）浓度变化;并将出现醛固酮逃逸的ACEI组患者分为螺内酯组、对照组,检测尿白蛋白排泄率（UAER）、血钾水平的变化。结果早期糖尿病肾病患者服用依那普利6个月后出现醛固酮逃逸现象,对此类现象加用螺内酯干预后患者的UAER比对照组明显降低（P〈0．05）,且没有出现明显的高钾血症。结论ACEI联合醛固酮受体拮抗剂可以更好地降低早期糖尿病肾病患者的UAER。     

肝细胞一氧化氮合酶的诱导及动力学研究

目的对内毒素和几种细胞因子诱导肝细胞一氧化氮合酶的协同效应及酶动力学参数进行研究.方法原位预灌流和段原酶循环灌流大鼠肝脏、分离肝实质细胞,观察内毒素、IFN-Y、IFN-α、TNFα、IL-lβ、IL-6及不同组合对肝细胞一氧化氮合酶活性、cGMP及NO2-+NO3的影响,分析酶动力学特征及皮质甾与酶诱导的量效关系.结果内毒素+IFN-v+TNFα+IL-lβ(IL-6)组合诱导酶表达效应最显著;酶参数分析显示Km、Vmax分别为108μmol/L和2632pmol@min1mg-1蛋白质,竞争性抑制剂L-NMMA、L-NNA作用的Ki分别为056μmolL及094μmol/L;诱导时间进程显示iNOS活性表达在9h达到峰值,但cGMP及NO2-NO3-的释放持续增加可维持至l8h;地塞米松和氢化可的松抑制肝细胞酶诱导的IC50分别为35×10-8mol/L和26×10-0mol/L.结论肝细胞诱导性一氧化氮合酶的表达依赖特异多细胞因子协同作用,这种可诱导性特征可能在内毒素血症和败血症休克发病机制中具有重要意义.     

Attenuation of the induction of nitric oxide synthase by endogenous glucocorticoids accounts for endotoxin tolerance in vivo.

An enhanced formation of nitric oxide (NO) due to induction of a calcium-independent (inducible) NO synthase (iNOS) contributes importantly to the cardiovascular failure caused by bacterial endotoxin. Repeated challenges with small doses of endotoxin result in tolerance to both peripheral vascular failure and death caused by subsequent injection of a higher dose of endotoxin. Here we investigate whether tolerance to endotoxin is associated with a lack of induction of iNOS in vivo and whether endogenous glucocorticoids play a role in the development of endotoxin tolerance. In anesthetized rats, i.v. administration of Escherichia coli endotoxin [lipopolysaccharide (LPS); 2 mg.kg-1] resulted in a prolonged decrease in mean arterial blood pressure (MAP) and hyporeactivity to the contractile responses elicited by norepinephrine (NE; 10 nM) in aortic rings ex vivo. Hyporeactivity to NE was partially reversed by NG-nitro-L-arginine methyl ester (0.3 mM) in vitro, suggesting that an enhanced formation of NO contributes to this hyporeactivity. There was a substantial increase in the activity of iNOS in the lung 3 h after i.v. injection of LPS (0.2 +/- 0.1 to 6.6 +/- 0.6 pmol.mg-1.min-1; n = 5; P < 0.01). Rats injected i.p. with LPS (0.5 mg.kg-1) for 4 consecutive days became tolerant to an i.v. injection of LPS (2 mg.kg-1) in that both hypotension and vascular hyporeactivity to NE were significantly attenuated. Moreover, in these endotoxin-tolerant rats, the induction of iNOS by LPS in the lung was attenuated by 63% +/- 6%. Injection of LPS caused a 9-fold increase in plasma corticosterone (CCS) levels within 2 h and CCS levels remained significantly elevated 6 and 24 h after LPS. Animals rendered tolerant to endotoxin by administration of a low dose of LPS (0.5 mg.kg-1, i.p.) for 4 days still had a 6-fold increase in plasma CCS levels 24 h after the last injection of LPS. When endotoxin-tolerant rats were treated with the glucocorticoid receptor antagonist RU 486 (50 mg.kg-1, p.o. 3 h prior to LPS), there was a restoration of the effects of LPS (2 mg.kg-1, i.v.) in causing hypotension, vascular hyporeactivity to NE, and iNOS induction in the lung. However, in control rats RU 486 enhanced neither the decrease in MAP nor the induction of iNOS in response to LPS (2 mg.kg-1, i.v.). Thus, cardiovascular tolerance to endotoxin is accompanied and explained by reduced induction of iNOS in vivo due to the elevation of endogenous glucocorticoid levels.     

一氧化氮及其合酶在哮喘发病机制中的作用

探讨一氧化氮及其合酶在哮喘发病机制中的作用。方法 采用哮喘豚鼠模型，将豚鼠分为４组；１．哮喘组，用１０％卵白蛋白腹腔注射１ｍｌ致敏，２周后用１％卵白蛋白超声雾化吸入致其哮喘发作．２；肾上腺皮质激素预防组；诱喘同哮喘组，在每次诱喘前腹腔滴注地塞米松０．５ｍｇ／ｋｇ。３．硝基精氨酸甲酯预防组；诱喘同哮喘组，每次诱喘产腹腔注射ＬＮＮＡ０．４ｍｇ／ｋｇ。４．正常对照组；用生理盐水代替诱喘剂。每组分别测定其     

一氧化氮对猪带绦虫六钩蚴细胞毒作用的研究

目的　研究一氧化氮 (NO)对猪带绦虫六钩蚴杀伤作用。方法　以LPS诱导离体的小鼠腹腔巨噬细胞 ,使其产生NO ;加入猪带绦虫六钩蚴 ,测定 4 8h内六钩蚴的死亡率 ;分别用诱导型一氧化氮合酶 (iNOS)的抑制剂地塞米松 (Dexam ethasone ,DXS)和左旋硝基精氨酸 (Nω -nitro -L -arginine ,L -NNA)抑制NO产生 ,与未加抑制剂组比较六钩蚴死亡率的变化。结果　LPS可有效诱导巨噬细胞产生NO ,2 0× 10 5巨噬细胞产生的NO浓度为 119 6 4 0 0 +5 115 4 μmol/L ,相应的杀虫率为 79 83%。加入抑制剂DXS和L -NNA后 ,巨噬细胞的NO产量均明显降低 ,其杀虫率也明显降低。结论　活化巨噬细胞产生的NO对猪带绦虫六钩蚴有杀伤作用。     

An inhibitor of inducible nitric oxide synthase decreases forearm blood flow in patients with congestive heart failure.

OBJECTIVES: The functional activation of inducible nitric oxide synthase (iNOS) was evaluated as a source of nitric oxide (NO) in the forearm of patients with heart failure. BACKGROUND: Although endogenous NO is normally produced by constitutive NO synthase (cNOS) in patients with congestive heart failure (CHF), expression of iNOS provides an additional source of NO. However, there are no in vivo studies showing functional activation of iNOS in humans. METHODS: A nonselective NOS inhibitor, N(G)-monomethyl-L-arginine (L-NMMA), and a selective inhibitor of iNOS, aminoguanidine, were administered intra-arterially in graded doses into the brachial arteries of 13 patients with CHF and 10 normal control subjects. Forearm blood flow (FBF) was measured simultaneously in the infused and noninfused arms by plethysmography. Arterial and venous plasma concentrations of nitrite/nitrate (NOx) were measured at baseline and at the highest dose of each drug. RESULTS: L-NMMA significantly reduced the FBF ratio between the infused and noninfused arms in both the control and patient groups (35 +/- 12% and 34 +/- 10%, respectively; both p < 0.001). Aminoguanidine at the same concentration significantly reduced the ratio in the patient group (15 +/- 9%, p < 0.01), with no change in the control group. The arterial NOx concentration was not affected by either drug; however, venous NOx concentrations were significantly decreased in both the control and patient groups by L-NMMA (18 +/- 5% and 18 +/- 17%, respectively; both p < 0.05) and in the patient group only by aminoguanidine (7 +/- 6%, p < 0.05). CONCLUSIONS: These findings suggest that NO production in the forearms of patients with CHF is induced partly by iNOS activation, whereas in normal subjects, it can be ascribed to cNOS activation.     

Mechanisms underlying growth hormone effects in augmenting nitric oxide production and protein tyrosine nitration during endotoxin challenge

The present study defined the effects of GH administration on components of the nitric oxide (NO)-generating cascade to account for observed increases in NO production and protein nitration after an immune challenge. Calves were assigned to groups with or without GH treatment (100 microg GH/kg body weight or placebo im, daily for 12 d) and with or without low-level endotoxin [lipopolysaccharide (LPS), 2.5 microg/kg, or placebo, iv]. Plasma was obtained for estimation of NO changes as [NO(2)(-) + NO(3)(-)] (NO(x)). Transcutaneous liver biopsies were collected for measurement of protein tyrosine nitration, cationic amino acid transporter (CAT)-2 mRNA transporter, and constitutive NO synthase (cNOS), inducible NOS (iNOS), and arginase activity. Liver protein nitration increased more than 10-fold 24 h after LPS and an additional 2-fold in animals treated with GH before LPS. GH increased plasma NO(x) after LPS to levels 27% greater than those measured in non-GH-treated calves. LPS increased CAT-2 mRNA after LPS; GH was associated with a 24% reduction in CAT-2 mRNA content at the peak time response. cNOS activity was 3-fold greater than iNOS after LPS. NOS activities were increased 140% (cNOS) at 3 h and 169% (iNOS) at 6 h, respectively, after LPS; GH treatment increased cNOS activity and the phosphorylation of endothelial NOS after LPS more than 2-fold over that measured in non-GH-treated calves. The data suggest that an increased production of nitrated protein develops in the liver during low-level, proinflammatory stress, and nitration is increased by GH administration through a direct effect on the competing activities of NOS and arginase, modulatable critical control points in the proinflammatory cascade.     

Endogenous endothelial nitric oxide synthase-derived nitric oxide is a physiological regulator of myocardial oxygen consumption

Our objective was to determine the precise role of endothelial nitric oxide synthase (eNOS) as a modulator of cardiac O2 consumption and to further examine the role of nitric oxide (NO) in the control of mitochondrial respiration. Left ventricle O2 consumption in mice with defects in the expression of eNOS [eNOS (-/-)] and inducible NOS [iNOS (-/-)] was measured with a Clark-type O2 electrode. The rate of decreases in O2 concentration was expressed as a percentage of the baseline. Baseline O2 consumption was not significantly different between groups of mice. Bradykinin (10(-4) mol/L) induced significant decreases in O2 consumption in tissues taken from iNOS (-/-) (-28+/-4%), wild-type eNOS (+/+) (-22+/-4%), and heterozygous eNOS(+/-) (-22+/-5%) but not homozygous eNOS (-/-) (-3+/-4%) mice. Responses to bradykinin in iNOS (-/-) and both wild-type and heterozygous eNOS mice were attenuated after NOS blockade with N-nitro-L-arginine methyl ester (L-NAME) (-2+/-5%, -3+/-2%, and -6+/-5%, respectively, P<0.05). In contrast, S-nitroso-N-acetyl-penicillamine (SNAP, 10(-4) mol/L), which releases NO spontaneously, induced decreases in myocardial O2 consumption in all groups of mice, and such responses were not affected by L-NAME. In addition, pretreatment with bacterial endotoxin elicited a reduction in basal O2 consumption in tissues taken from normal but not iNOS (-/-)-deficient mice. Our results indicate that the pivotal role of eNOS in the control of myocardial O2 consumption and modulation of mitochondrial respiration by NO may have an important role in pathological conditions such as endotoxemia in which the production of NO is altered.     

L-arginine partially reverses established adrenocorticotrophin-induced hypertension and nitric oxide deficiency in the rat

BACKGROUND: L-arginine treatment prevents adrenocorticotrophin (ACTH) induced hypertension in the rat. This study examined whether L-arginine treatment could reverse established ACTH hypertension and its effects on markers of decreased NO activity. METHODS: Sixty-four male Sprague-Dawley rats were randomly divided into 6 groups given 12 days of treatment: (1) sham (0.9% NaCl, 0.5 ml/kg, subcutaneously, sc, n = 16); (2) ACTH (0.5 mg/kg/day, sc, n = 16); (3) sham + L-arginine (0.6% in food, from treatment day 8 onwards, n = 10); (4) ACTH + L-arginine (n = 10); (5) sham + D-arginine (0.6% in food, from T 8 onwards) (n = 6); and (6) ACTH + D-arginine (n = 6). Systolic blood pressure, water intake, urine volume, and body weight were measured every second day. At the end of the experiments, plasma and urinary nitrate/nitrite (NOx), plasma amino acid concentrations (in groups 1-4), and urinary cyclic guanosine monophosphate (cGMP) concentrations were measured. RESULTS: Sham, sham + L-arginine, and sham + D-arginine treatments did not affect blood pressure. ACTH increased systolic blood pressure (from 121 +/- 1 to 147 +/- 2 mmHg, p < 0.001, pooled control vs treatment day 12, mean +/- sem), and this was partially reversed by L-arginine (group 4: from 141 +/- 2 on day 8 to 133 +/- 1 mmHg on day 12, n = 10, p < 0.001). In contrast, D-arginine did not affect blood pressure in ACTH-treated rats (group 6). ACTH increased water intake and urine volume and decreased body weight, and L-arginine administration did not alter these parameters. ACTH decreased plasma citrulline (group 1 vs 2: 115 +/- 7 vs 67 +/- 6 micro M/L, n = 16, p < 0.001) and NOx concentrations (group 1 vs 2: 8.3 +/- 0.8 vs 4.5 +/- 0.6 microM/L, n= 10, p < 0.001) and these decreases were reversed by L-arginine treatment (group 4: citrulline 98 +/- 9 micro M/L, NOx 9.1 +/- 1.6 micro M/L, group 2 vs 4, both p < 0.05). ACTH produced marked increases in urinary cGMP excretion (group 1 vs 2: 0.5 +/- 0.1 vs 1.9 +/- 0.4 nmol/24 h, p < 0.01). CONCLUSION: Supplementation with L-arginine partly reversed established ACTH-induced hypertension and restored plasma NOx and citrulline concentrations to levels seen in sham-treated rats. These data are consistent with previous studies suggesting that functional NO deficiency has a role in ACTH-induced hypertension in rats.     

Expression of inducible nitric oxide synthase and effects of L-arginine on colonic nitric oxide production and fluid transport in patients with "minimal colitis"

OBJECTIVE: Some patients with idiopathic, chronic diarrhoea have minimal, non-specific colonic inflammation. As nitric oxide (NO) acts as a secretagogue in the colon, we studied the expression of inducible NO synthase (iNOS) in mucosal biopsies and the effects of NOS stimulation on colonic transfer of fluid and output of NO in patients with "minimal colitis". MATERIAL AND METHODS: Twelve patients with idiopathic, chronic diarrhoea and "minimal colitis" and 6 healthy volunteers were included in the study. Expression of iNOS in colonic mucosal biopsies was quantified by Western blot analysis and localized by immunohistochemistry. The effects of topical L-arginine or placebo on colonic net fluid transfer and nitrite/nitrate (NOx) output were assessed during "steady state" perfusion of the whole colon. Concentrations of NOx were measured by Griess' assay. RESULTS: The expression of iNOS was increased 10-fold (p<0.01) in patients with "minimal colitis" compared with that in healthy volunteers and localized to the colonic epithelium. Colonic absorption of fluid was impaired (mean (SEM) 1.5 (0.2) versus 3.0 (0.2) ml/min, p<0.001) and the output of NOx was increased (47 (4) nmol/min versus <37 nmol/min, p<0.05) in patients with "minimal colitis" compared with that in healthy volunteers. Luminal L-arginine (20 mM) reduced colonic absorption of fluid in both groups (95% confidence intervals (CIs) 21-50% in patients with "minimal colitis" versus 4-18% in healthy volunteers), but an increase in NOx output was detectable only in the group of patients (8-106%). In time control experiments, colonic net transfer rates of fluid and outputs of NOx were unaffected by placebo. CONCLUSIONS: In patients with idiopathic, chronic diarrhoea and histopathological evidence of "minimal colitis", colonic absorption of fluid is impaired, while epithelial expression of iNOS and mucosal production of NO is enhanced. It could be speculated that NO in excess contributes to the diarrhoea observed in "minimal colitis".     

The plasma level of nitric oxide and the expression of inducible nitric oxidesynthase in human hepatocellular carcinoma

AIM To study the relationship between nitric oxide (NO), nitric oxide synthase (NOS) and humanhepatocellular carcinoma (HCC).METHODS Plsama NO2-/NO3- was measured by Griess reaction in 122 patients with chronic hepatitis(CH) and compensated liver cirrhosis (LC), among which 62 patients were complicated with HCC(CH = 28, LC = 34), and the rest 60 patients were not (CH = 29, LC = 31). Thirty healthy persons served asnormal controls (NC). There were no prominent differences among the groups in sex, age and the ratio ofCH to LC. The expression of inducible nitric oxide synthase (iNOS) in HCC (n = 40), CH (n = 30) and LC(n = 30) samples obtained from liver biopsy or operation was compared with that in normal liver tissues byusing immunohistochemistry. Ten normal liver tissue samples obtained from liver operation served as normalcontrols. The samples were fixed in formalin and embeded in paraffin. Anti-iNOS antibody (Santacruzcompany) was served as antibody-Ⅰ in immunohistochemical assay of iNOS in tissue.RESULTS Plasma NO2-/NO3- level in normal was 11.5 μmol/L±4.2μmol/L. The plasma level ofNO2 /NO3- in CH (58.6±17.4 μmol/L) and LC (38.7±10.6μmol/L) accompanied with HCC wasnotably higher than in those patients without HCC (CH: 24.8±9.4 μmol/L; LC: 22.3±8.7μmol/L,t=2.901, 2.756, P<0.01). Plasma NO2-/NO3- level in HCC accompanied with CH was significantlyhigher than in those accompanied with LC ( t = 2.216, P<0.05). Positive rate of iNOS in HCC, CH and LCwas 95%, 93% and 57% respectively. iNOS was not expressed in normal liver tissues. The expression level ofiNOS in HCC (χ2=17.4, P<0.001) and CH (χ2=11.64, P<0.025) was much higher than in LC.CONCLUSION Plasma NO2 / NO3- level significantly increased in patients with HCC and theimmunohistochemical staining of iNOS was positive. This suggests that the liver secrets NO in the higherlevel may participate in the carcinogenesis and progression of HCC.