大鼠脊髓损伤后一氧化氮合酶基因表达的变化

目的　探讨大鼠脊髓损伤后3种类型一氧化氮合酶（NOS）mRNA表达的变化规律。方法　成年SD大鼠36只,随机分为种类6组,每组6只大鼠。建立大鼠脊髓压迫伤模型,以逆转录-聚合酶链反应（RT-PCR）法测定伤段脊髓组织神经型（nNOS）、诱导型（iNOS）及内皮型（eNOS）一氧化氮合酶的mRNA表达情况。结果　脊髓压迫伤后nNOSmRNA及NOSRNA表达增强,伤后6h达到高峰0.633±0.012、1.236±0.207;iNOSmRNA表达亦增高,但在伤后24h才达到高峰1.043±0.049。结论　脊髓损伤后NOSmRNA的表达增强,但不同类型的NOSmRNA变化规律不同,增强或抑制不同NOSmRNA的表达可能减轻脊髓继发性损伤。     

Gene expression of inducible nitric oxide synthase in injured spinal cord tissue

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丹参对大鼠缺血再灌注肾组织一氧化氮合成酶mRNA表达的影响

目的：探讨丹参对肾缺血再灌注损作保护效应的分子机制。方法：以大鼠缺血再灌汪肾损伤为模型，采用组织细胞原位杂交有图像分析技术技术，检测cNOS（eNOS和nNOS）及iNOSmRNA在缺血再灌注肾组织中的表达，并测定肾组织NOS总活性有血肌酐（Cr）。结果：①3种NOS在正常肾组织中均有表达，其中eNOS表达最丰富，cNOS／iNOS比值为2．29。②缺血时，肾组织NOS总活性显著下降，3种NOSmRNA在皮质、髓质有小球中的表达均下调，以eNOS最显著，cNOS／iNOS比值呈下降（2．01）趋势。③再灌注后，3种NOSmRNA的表达明显上调，以iNOSmRNA最明显，cNOS／iNOS的比值降至1．77。④肾缺血注射丹参后再灌注，iNOSmRAN表达明显下调，而nNOSmRAN则显著上调，cNOS／iNOS比值处于正常范围（2．14），Cr含量下降至正常水平。结论：①皮质肾小管上皮中iNOS活性升同与再灌汪后肾功能进一步受损密切相关。②缺血再灌注肾损伤中，丹参抑制iNOSmRNA和促进cNOSmRNA的表达是其介导肾保护效应的重要分子机制。③cNOS／iNOS比值的恒定对肾血流量和肾小球滤过率（GFR）的调节可能具有重要的意义。     

The role of constitutive nitric oxide synthase in pathogenesis of secondary lesion after spinal cord injury. Preliminary results

BACKGROUND: Secondary lesion (SL) is an early phenomenon of cellular death following spinal cord injury (SCI). Nitric oxide (NO) could be involved in its pathogenesis. NO is a gaseous metabolite produced by 2 constitutive isoforms of NO synthase (cNOS), constantly active, and by 1 inducible isoform (iNOS), synthesized during inflammation and able to produce large amount of NO. High concentrated NO is toxic for cells; therefore, NO concentration is strictly and finely regulated. We suppose that major inhibitory effect on the iNOS expression is represented by the same physiological concentration of NO, synthesized by cNOS. The aim of this study is to assess the role of the 2 cNOS in pathogenesis of SL after SCI in rat. METHODS: A dorsal SCI has been performed on rats (n=5) by a vascular clip (50 g/mm(2) for 15"). Fifteen minutes after trauma, activity of nNOS and eNOS has been measured (U/mg) in the cervical, dorsal and lumbar segments of spinal cord. Uninjured rats (n=5) served as control group. m-RNA for iNOS in untreated rats (n=2) has been also investigated by Northern blotting. RESULTS: In injured rats nNOS activity has shown a reduction in dorsal and lumbar segments, compared to the control group. eNOS activity, highly variable in the control group, has not been detectable in injured spinal cord. i-NOS mRNA has not been found in spinal cord of uninjured rats. CONCLUSIONS: These results would be in line with our hypothesis and provide the bases for other investigations. New therapeutic strategies for SL prevention, based on the modulation of cNOS, will be evaluated.     

电针对神经病理性痛大鼠脊髓NO/cGMP信号转导通路的影响

目的 探讨电针对神经病理性痛大鼠脊髓一氧化氮/环鸟苷酸(NO/cGMP)信号转导通路的影响.方法 清洁级雄性SD大鼠48只,体重190～210 g,随机分为3组(n=16):假手术组(S组)仅分离坐骨神经,不结扎;神经病理性痛组(NP组)采用坐骨神经慢性压迫性损伤(CCI)法制备神经病理性痛模型;电针组(E组)于CCI后11～17 d时采用穴位神经刺激仪进行电针刺激,刺激大鼠术侧委中穴与环跳穴,刺激频率2 Hz,波宽0.6 ms,起始电流强度1 mA,每10 min递增1 mA,刺激时间30 min,1次/d.于CCI前(基础状态)、CCI后10、16 d时测定机械痛阈和热痛阈.CCI后10 d时痛阈低于基础痛阈的30%为模型制备成功.CCI后17 d时处死大鼠,取脊髓组织,采用分光光度法测定脊髓总一氧化氮合酶(tNOS)、诱导型一氧化氮合酶(iNOS)和神经元型一氧化氮合酶(nNOS)的活性,免疫组化法测定脊髓背角nNOS和iNOS的表达,采用硝酸还原酶法测定脊髓NO含量,采用放射免疫分析法测定脊髓cGMP含量.结果 与基础值比较,NP组和E组CCI后机械痛阈和热痛阈降低(P＜0.01);与CCI后10 d时比较,E组CCI后16 d时机械痛阈和热痛阈均升高(P＜0.01);与S组比较,NP组机械痛阈和热痛阈降低,脊髓tNOS、nNOS活性、NO和cGMP含量升高,nNOS表达上调,E组机械痛阈和热痛阈降低(P＜0.05或0.01),其余指标差异无统计学意义(P＞0.05);与NP组比较,E组机械痛阈和热痛阈升高,脊髓tNOS和nNOS活性、NO和cGMP含量降低,nNOS表达下调(P＜0.05或0.01).3组脊髓iNOS活性和表达比较差异无统计学意义(P＞0.05).结论 电针减轻大鼠神经病理性痛的机制与抑制脊髓NO/cGMP信号转导通路有关.     

Modulation of nitric oxide synthase isoenzymes inreperfused skeletal muscle

Objective:To investigate the modulation of nitric oxide synthase(NOS)isoenzymes in skeletal muscle during 3h ischemia/reperfusion (I/R,3h ischemia followed by 3h reperfusion).Methods:The extensor digitorum longuses(EDLs) from 20 adult rats were divided into 4 groups:the normal,the sham operation,the ischemia(3h),and the ischemia/reperfusion group.One normal EDL from each rat was used as the non-operated control,and the opposite ones are distributed into the 3 remaining groups.All the samples were studied with Western blotting technique and immunohistochemistry staining.Results:Three sizes or protein bands verified with the proteins of relative molecule to be of 155000,140000 and 135000,were detected in the EDL homogenate by Western blotting,which were comparable with the positive controls for nNOS,eNOS and iNOS,respectively.Immunostaining demonstrated that nNOS was present in the muscle fiber,with a similar location of the muscle stria,eNOS was found apparently in microvascular endothelia,but not found in muscle fibers,and iNOS was found in the leukocytes around the muscle fiber and some endothelia cells.Immunostaining paralleled the Western blotting results.Conclusions:It suggests that the constitutive nNOS and eNOS protein can be regulated by I/R,and I/R results in a down regulation of nNOW and up-regulation of eNOS and iNOS in reperfused skeletal muscle.The fact that nNOS is present around stria suggests that nNOS may have a close relationship with muscle function.The localization of eNOS in endothelial cell indicates its role in regulating blood supply of the muscle.Based on these findings,it is possible that No produced by distinct NOS may play a different role in I/R injury.     

卡托普利对缺血-再灌注鼠心肌一氧化氮及其合酶活性的影响

目的　研究一氧化氮 (NO)和一氧化氮合酶 (NOS)在心肌再灌注损伤中的作用 ,探讨卡托普利(captopril)对缺血 -再灌注鼠心肌保护的机制。　方法　采用 L angendorff离体鼠心灌流模型 ,将 18只 SD大白鼠随机分为 3组 (每组 6只 ) ,对照组、缺血 -再灌注组、卡托普利组。观察心肌 NOS同工酶活性、过氧化物歧化酶活性、丙二醛含量、肌酸激酶含量和冠脉流出液 NO的变化。　结果　缺血 -再灌注组与对照组比较心肌诱导型 NOS(i NOS)活性增高 (P<0 .0 0 1) ,而心肌原生型 NOS(c NOS)活性及总 NOS活性显著降低 (P<0 .0 0 1,0 .0 5 ) ,冠脉流出液 NO含量下降(P<0 .0 1)。卡托普利组再灌注 30分钟 ,心肌 i NOS活性低于缺血 -再灌注组 (P<0 .0 1) ,c NOS活性和总 NOS活性高于缺血 -再灌注组 (P<0 .0 1,0 .0 5 ) ,再灌注期间冠脉流出液 NO水平高于缺血 -再灌注组 (P<0 .0 1) ,心肌损伤较缺血 -再灌注组减轻。　结论　心肌 NOS同工酶活性及 NO产生的失常是心肌再灌注损伤的重要机制之一 ,卡托普利可通过调节心肌 NOS同工酶活性 ,维持正常的 NO水平 ,起到心肌保护作用。     

Changes in nitric oxide synthase expression in young and adult rats after spinal cord injury

OBJECTIVE: To examine the clinical meaning of the changes in nitric oxide synthase (NOS) expression and activity after spinal cord injury (SCI) according to the age of the experiment animal. MATERIAL AND METHOD: Ten 5- and 16-week-old Sprague-Dawley rats were laminectomized at T10 and SCI induced at this level using a New York impactor. Outcome measures to assess SCI utilized the Basso-Beatti-Bresnahan scale to quantitate hind limb motor dysfunction as a functional outcome measure. NOS isoforms (nNOS, neuronal NOS; iNOS, inducible NOS; and eNOS, endothelial NOS) were also immunolocalized in sections of control and spinal cord injury in the two sample groups using specific monoclonal antibodies. Student's t-test evaluated the difference between the young and adult rats, and P<0.05 was considered as significant value. RESULT: As the expression of nNOS on the spinal gray matter of the adult rat decreased, eNOS activity increased. Different from the adult rat, expression of the nNOS in the young rat was maintained until 1 day after SCI, and compared with the adult rat; eNOS activity was increased in the vessels from the damaged gray matter area after 7 days of SCI. iNOS expression was maintained until the 7th day of SCI on the adult rat, but iNOS expression after 7 days of SCI on young rat decreased. The young rat showed relatively less motor disability on the hind limb when compared with the adult rat, and had a rapid recovery. CONCLUSION: Neural protective eNOS activity increased after SCI in the young rat, and neural destructive iNOS expression was more remarkable in the adult rat.     

神经源性膀胱组织中一氧化氮合酶表达的特点和意义

目的 探讨神经元型一氧化氮合酶(nNOS)、诱导型NOS(iNOS)和内皮型NOS(eNOS)在神经源性膀胱组织中表达状况,探讨一氧化氮在神经源性膀胱组织中产生及作用特点.方法 神经源性膀胱患儿30例.男18例,女12例.年龄(6.3±3.1)岁.30例均行手术治疗,术中留取膀胱组织标本,采用免疫组织化学方法检测膀胱组织中nNOS、iNOS和eNOS表达状况,10例正常膀胱组织标本作对照. 结果 正常膀胱体部组织nNOS阳性表达,走行在平滑肌纤维之间,分布于平滑肌细胞表面,膀胱基质也有表达,组织化学评分(HS)为2.8～4.0和1.2～2.7;平滑肌细胞iNOS阴性表达,平滑肌细胞基质有少量稀疏表达,HS为0～0.4和0～0.1;eNOS表达分布于血管内皮细胞中,分布稀疏,平滑肌细胞无表达.膀胱颈部组织表达高于膀胱体部组织,以nNOS表达为主.神经源性膀胱组织中以iNOS表达为主,nNOS表达明显减少;eNOS主要分布于膀胱基质的内皮细胞,膀胱平滑肌、成纤维细胞阴性表达;病变膀胱组织血管稀疏,微血管密度100倍视野下可见到(6.8±3.2)个血管灶,低于正常膀胱组织的(16.7±6.3)个(P＜0.01).结论 正常膀胱组织nNOS主要分布在膀胱颈中,NO合成主要受nNOS调节.神经源性膀胱患者膀胱组织中氮能神经元分布稀疏,nNOS表达减少,iNOS表达上调,NO的合成与调节可能主要来源于iNOS,受iNOS水平调节,eNOS表达下降,提示膀胱组织血供不良.     

一氧化氮合成酶在周围神经的表达

目的 研究一氧化氮合成酶（ｎｉｔｒｉｃ ｏｘｉｄｅ ｓｙｎｔｈａｓｅ,ＮＯＳ）的三种同工酶在大鼠坐骨神经中的表达和分布情况。方法 取１０只ＳＤ大鼠双侧正常坐骨神经,一侧用于Ｗｅｓｔｅｒｎ印迹检查,另外一侧用于免疫组化检查。结果 Ｗｅｓｔｅｒｎ印迹法中,用神经元型一氧化氮合成酶（ｎｅｕｒｏｎａｌ ＮＯＳ,ｎＮＯＳ）单抗和内皮细胞型一氧化氮合成酶（ｅｎｄｏｔｈｅｌｉａｌ ＮＯＳ,ｅＮＯＳ）单抗,分别发     

早期肠道喂养对烧伤大鼠肠道一氧化氮合酶的影响

目的阐明烧伤大鼠经早期肠道喂养后肠组织中一氧化氮合酶(NOS)的变化规律及其与肠粘膜血流量(IMBF)的关系。方法采用30％TBSAⅢ度烧伤大鼠模型,分为正常对照(C)组,单纯烧伤(B)组和早期喂养(EF)组,分别检测伤前及伤后0,3,6,12,24,48小时肠组织中 NOS 活性,包括原生型 NOS(cNOS)和诱导型 NOS(iNOS),并测定肠粘膜血流量。结果烧伤后各组 cNOS 和 IMBF 呈下降趋势,二者呈显著正相关(r=0.97,P<0.01),而 NOS 总活性和 iNOS 活性都呈上升趋势,IMBF 与 iN-OS 和总 NOS 相关不显著。烧伤后 EF 组 cNOS 和 IMBF 明显高于 B 组,iNOS 则低于 B 组,NOS 总活力两组无显著差异。结论①两型 NOS 中 cNOS 与 IMBF 的关系更加密切。②早期肠道喂养改善烧伤后肠道缺血状况,可能与食物对肠壁神经的刺激从而提高 cNOS 活性有关。     

一氧化氮和一氧化氮合酶在急性大面积脑梗死患者中的表达

目的 观察一氧化氮(NO)和一氧化氮合酶(NOS)在急性大面积脑梗死患者去骨瓣术后的表达.方法 急性大面积脑梗死患者16例(脑梗死组),均采用全麻开颅去骨瓣减压手术,手术中切除部分梗死额叶组织;以6例重型颅脑外伤行正常额叶组织内减压为对照组.2组均采用透视电镜观察额叶细胞超微结构,检测NO含量和NOS活性,Western blot法分析内皮型NOS(eNOS)、神经元型NOS(nNOS)和诱导型NOS(iNOS)蛋白表达特点.结果　本组病例16例脑梗死患者术后神志不同程度改善,无死亡病例;NO含量在脑梗死组和对照组分别为85.4U/ml和36.2U/ml,NOS活性在脑梗死组和对照组分别为63.2 μmol/L和37.2 μmol/L,差异均有统计学意义(P＜0.05);与对照组比较,eNOS、nNOS和iNOS在脑梗死组中表达均明显升高,尤其是iNOS表达相对值为0.76,远远超过对照组未见表达,差异均有统计学意义(P＜0.05).结论　去骨瓣减压是治疗急性大面积脑梗死的有效治疗手段,能够降低患者死亡率;NO和NOS参与并影响了大面积脑梗死后复杂的病理生理过程,去骨瓣减压后局部脑血供得到有效改善,NOS活性减低,尤其iNOS活性明显减少,合成NO减少,神经毒性减低,临床症状好转.

Abstract：

Objective To study the expression of nitric oxide (NO) and nitric oxide synthase (NOS) in patients with acute massive cerebral infarction. Methods Sixteen patients (cerebral infarction group) with acute massive cerebral infarction were subjected to craniotomy decompression craniectomy under the anesthesia, and part of the infarct frontal lobe was removed. The normal frontal lobe from 6 cases of severe brain injury receiving the intracranial decompression served as control group. The ultrastructures of frontal lobe cells were observed under the electron microscopy. Serum NO content and NOS activity were measured. The protein expression patterns of eNOS, nNOS and iNOS were analyzed by Western blotting.Results The consciousness in 16 patients with acute massive cerebral infarction was improved after operation to varying degrees, and there were no deaths. The NO contents and NOS activities in cerebral infarction group and control groups were 85.4 and 36. 2 U/mi, and 63.2 and 37.2 μmol/L ( all P ＜ 0. 05). As compared with control group, the expression of eNOS, nNOS and iNOS in cerebral infarction group was significantly increased, especially the expression of iNOS ( all P ＜ 0. 05). Conclusion Craniotomy decompression craniectomy was the effective treatment to cure the acute massive cerebral infarction. It could reduce mortality. NO and NOS participated in and influenced the complex pathophysiological process of massive cerebral infarction. After craniotomy decompression craniectomy the regional cerebral blood was effectively improved, and NOS activity, especially iNOS, and the synthesis of NO were reduced, resulting in the reduction to neurotoxicity and improvement in clinical symptoms.     

针刀干预对L3横突综合征模型大鼠骨骼肌NOS及NO的影响

目的：研究L3横突综合征模型大鼠损伤局部软组织NOS活性及NO含量与软组织损伤程度的关系,并观察针刀干预后的影响。方法：成年雄性SD大鼠128只随机分为正常组、模型组、氨基胍组、针刀组,每组32只。建立L3横突综合征动物模型,造模后14d,对造模局部软组织的硬结和条索状物无菌条件下用一次性针刀行纵行切割3刀,横行切割1刀,随即出针刀。氨基胍组从造模14d开始,按50mg/kg剂量经腹膜内给药,2次/d,直至处死前一天为止。通过针刀、氨基胍干预后在1、3、7、14d检测各组L3横突周围软组织NOS活性、NO含量及观察组织形态学变化。结果：①模型组iNOS活性及NO含量比正常组明显升高（F=522.860,P〈0.01）,针刀组、AG组比模型组明显降低（FiNOS=28.894,P〈0.01）,且各组iNOS活性及NO含量与损伤局部炎症反应及组织损伤程度相一致。②模型组、针刀组eNOS阳性表达增强,7d达到峰值,针刀组与模型组比较差异有统计学意义（FeNOS=3.454,P〈0.05）。③模型组、氨基胍组、针刀组nNOS阳性表达较高,组间比较无统计学意义（FnNOS=0.962,P〉0.05）。结论：针刀干预后可明显抑制高浓度NO的生成,减轻损伤软组织炎症反应和损伤程度,改善微循环,防止病理性瘢痕组织的形成,对慢性软组织损伤动物模型有明显的促修复作用。     

一氧化氮合酶在大鼠大肠癌细胞中的表达及意义

目的研究一氧化氮合酶(NOS)在大鼠大肠癌发生中的表达情况。方法应用免疫组化技术检测1，2二甲基肼(1，2-DMH)诱导的Wistat大鼠大肠癌模型中内皮型NOS(eNOS)，神经元型NOS(nNOS)和诱生型NOS(iNOS)在正常黏膜和大肠癌中的表达情况。结果eNOS和nNOS在正常黏膜中表达，在大肠癌中不表达；iNOS在正常黏膜中表达率很低(10%)，在大肠癌中高表达(87％)。结论在1，2-DMH诱导的大肠癌模型中，iNOS表达与大肠癌的发生关系密切。     

Effects of nerve growth factor on neuronal nitric oxide production after spinal cord injury in rats

OBJECTIVE: To explore the protective effects of nerve growth factor (NGF) on injured spinal cord. METHODS: The spinal cord injury (SCI) model of Wistar rats was established by a 10 gx2.5 cm impact force on the T(8) spinal cord. NGF (60 microg/20 microl) was given to the rats of the treatment group immediately and at 2, 4, 8, 12, 24 hours after SCI. The level of neuronal constitutive nitric oxide synthase (ncNOS) and the expression of ncNOS mRNA in the spinal cord were detected by the immunohistochemistry assay and in situ hybridization method. RESULTS: Abnormal expression of ncNOS was detected in the spinal ventral horn motorneuron in injured rats. The levels of ncNOS protein in the NGF group were significantly lower than those in the normal saline group (P<0.05 ). The ncNOS mRNA expression was found in the spinal ventral horn motorneuron in injured rats and the expression in the NGF group was significantly decreased compared with that in the normal saline group (P<0.01). CONCLUSIONS: NGF can protect the injured tissue of the spinal cord by prohibiting abnormal expression of nitric oxide synthase and the neurotoxicity of nitric oxide.     

大鼠睾丸内一氧化氮合酶的表达

目的 :阐明一氧化氮合酶 (NOS)在睾丸内的表达 ,探讨一氧化氮 (NO)在睾丸生殖功能中的作用。　方法 :取雄性SD大鼠睾丸于 4 %多聚甲醛中固定 ,常规石蜡切片。用免疫组化ABC法检测成年大鼠睾丸NOS的表达和定位。　结果 :内皮型NOS(eNOS)、神经型NOS(nNOS)、诱导型NOS(iNOS)在睾丸间质细胞内均有表达 ,精曲小管周围肌样细胞、血管内皮细胞和平滑肌细胞内仅为eNOS免疫反应阳性 ,而血管外膜纤维内仅有nNOS表达。免疫反应物质主要定位于细胞质 ,胞核为阴性。在生精细胞内 3种NOS免疫反应均为阴性。　结论 :3种NOS在睾丸内均有表达 ,不同的NOS分布部位有一定区别     

Nitric oxide synthase and renin–angiotensin gene expression and NOS function in the postnatal renal resistance vasculature

Nitric oxide (NO), produced by nitric oxide synthase (NOS), critically counteracts angiotensin-II-enhanced vascular resistance in the immature kidney, perhaps due to the developmental regulation of NOS expression and function in the postnatal preglomerular resistance vessels (PRV). Our experiments measured the messenger ribonucleic acid (mRNA) gene expression of neuronal NOS (nNOS), endothelial NOS (eNOS), and components of the renin-angiotensin system (renin, AT1 and AT2 receptors), by real-time RT-PCR, as well as NOS enzymatic activity by citrulline assay in PRVs (afferent, interlobular, and arcuate arterioles) obtained from swine ages newborn, 7 and 21 days, and adult. NOS enzymatic activity was upregulated in PRVs immediately after birth but decreased to adult levels with maturation. Neuronal NOS, renin, and AT2 receptor expression in PRVs were upregulated in the newborn and decreased with age to lowest levels in the adult. In contrast, eNOS and AT1 receptor expression were downregulated at birth but increased to the highest levels in the adult. Upregulated NOS enzymatic activity in newborn PRVs supports the critical neonatal role for NO renal vascular vasodilation. Upregulated nNOS gene expression, concomitant with downregulated eNOS gene expression in neonatal PRVs, suggests that the nNOS isoform may be responsible for counteracting angiotensin II increased vascular resistance in immature porcine PRVs.     

一氧化氮及其合酶在心肌缺血再灌注损伤中作用的研究

目的：用鼠的离体工作心脏研究心肌缺血再灌注损伤一氧化氮（ＮＯ）、ＮＯ合酶（ＮＯＳ）的作用。方法：ＲＴ－ＰＣＲ定量检测心肌组织结构型ＮＯＳ（ｃＮＯＳ）的ｍＲＮＡ表达,测定心肌组织的ｃＮＯＳ、诱导型ＮＯＳ（ｉＮＯＳ）及冠状动脉动脉冠脉）流出液的ＮＯ,同时检测心脏缺血再灌注前后的心功能变化。并分别于次序停跳液中加用缓激肽（ＢＫ）、Ｌ－精氨酸及ＢＫ加Ｌ－精氨酸,观察其对心肌缺血再灌注损伤的影响。结果：心肌     

Involvement of endothelial nitric oxide synthase in the impaired endothelium-dependent relaxation of cavernous smooth muscle in hypercholesterolemic rabbit

The present study was designed to evaluate whether functional impairment and/or protein expression of constitutive nitric oxide synthase (cNOS; endothelial NOS [eNOS] and neuronal NOS[nNOS]) was involved in impairment of endothelium-dependent relaxation of cavernous smooth muscle in hypercholesterolemic rabbits. New Zealand White rabbits were randomly divided into control and experimental groups. The control group (n=20) received a regular diet, while the two experimental groups (n=20 for each) were fed a 2% cholesterol diet for 4 and 8 weeks, respectively. We conducted isometric tension studies with endothelium-dependent and endothelium-independent vasodilators with or without preincubation with L-arginine and nonadrenergic, noncholinergic (NANC)-selective electrical field stimulation on isolated strips of corpus cavernosum. Expression of cNOS (eNOS and nNOS) protein was assessed by Western blot analysis. cNOS activities in both cytosolic and particulate fractions were measured by determining the conversion of L-[U-14C] arginine to L-[U-14C] citrulline. Blood levels of cholesterol were significantly higher (P < 0.01) in the experimental groups than in the control group. The relaxation responses to endothelium-dependent agents (acetylcholine and adenosine 5'-diphosphate [ADP]) were significantly reduced (P < 0.05) in both experimental groups, regardless of their incubation with L-arginine, compared with the control group. However, no differences were found among the three groups in the relaxation response to endothelium-independent agents (papaverine and nitroprusside) and to NANC-selective electrical field stimulation. There was no difference in immunoreactive nNOS from cytosolic and particulate fractions between the cavernous tissues of the control and experimental groups. nNOS protein levels in the particulate fractions were markedly lower than in the cytosolic fractions. The particulate cNOS activity was significantly decreased (P < 0.05) in the experimental groups compared with the control group, while the cytosolic cNOS activity in the experimental groups was not different from that found in the control group. Therefore, it is concluded that functional impairment of eNOS, rather than of nNOS, may lead to impairment of cavernous smooth muscle relaxation in response to endothelium-mediated stimuli in hypercholesterolemic rabbits.