Role of the L-arginine/nitric oxide pathway in renal ischaemia-reperfusion in rats.

OBJECTIVE: To study the role of the L-arginine/nitric oxide (NO) pathway during renal ischaemia-reperfusion in rats. DESIGN: Randomised experimental study. SETTING: Teaching hospital, Brazil. ANIMALS: 97 male Wistar rats randomly assigned to 4 groups for the assessment of renal dysfunction and to 6 groups for the assessment of the oxidative stress induced on renal cell membranes by ischaemia-reperfusion. INTERVENTIONS: The animals underwent sham-operation or renal ischaemia-reperfusion (n = 9 each) with or without pretreatment with L-arginine (a NO donor) or L-NAME (N(omega)-nitro-L-arginine methyl ester--an inhibitor of NO production) (n = 10 each). MAIN OUTCOME MEASURES: Serum creatinine concentrations and oxidative stress by chemiluminescence initiated by the tert-butyl hydroperoxide technique. RESULTS: Renal ischaemia-reperfusion significantly worsened renal dysfunction and increased oxidative stress in the ischaemia-reperfusion group after 24 and 96 hours of reperfusion compared with the control group (p < 0.05). Pretreatment with L-NAME slightly but not significantly increased serum creatinine concentrations after 24 and 96 hours of reperfusion together with activity of reactive oxygen species during renal ischaemia-reperfusion. L-arginine also significantly protected renal function and reduced the increment in the amount of chemiluminescence induced by giving L-NAME during 24 and 96 hours of reperfusion (p < 0.05). CONCLUSION: The L-arginine/NO pathway seems to have a slightly protective effect on the kidney after renal ischaemia-reperfusion injury in rats. These results need to be confirmed by studies in human beings.     

Effect of inhaled L-arginine on exhaled nitric oxide in normal and asthmatic subjects

BACKGROUND—Nitric oxide (NO) plays an importantpart in the regulation of many physiological functions and may also beinvolved in several pulmonary diseases. Endogenous NO is synthesised bydifferent isoforms of NO synthase (NOS) from L-arginine.
METHODS—The effect of inhaledL-arginine 0.75 g (six normal and six asthmatic subjects),1.5 g (six normal and six asthmatic subjects), and 3 g (seven normaland six asthmatic subjects) has been studied in a double blind placebocontrolled, randomised, parallel group design study. In addition, theeffect of a single dose (3 g) of inhaled L-alanine hasbeen assessed in five normal and five asthmatic subjects.
RESULTS—L-arginine increased exhaledNO in a dose-dependent fashion with a maximum at 60 minutes. Thecumulative effect of L-arginine (3 g) on NO in asthmaticsubjects, expressed as the area under the curve in arbitrary units (au)and compared with the effect of placebo (0.9% NaCl), was significantlyhigher (mean 0.11 au; 95% confidence interval (CI) 0.03 to 0.19) thanin normal subjects (0.012 au; 95% CI 0.002 to 0.022). There was anegative correlation (r = -0.72) between the increase inexhaled NO and the fall in forced expiratory volume in one second(FEV₁) (0.034 au, 95% CI 0.030 to 0.038) after 3 gL-arginine in asthmatic subjects. Inhalation of 3 g ofL-alanine produced a similar reduction in FEV₁(0.033au, 95% CI 0.007 to 0.059) but no significantly differentchanges in exhaled NO (0.017 au, 95% CI 0.001 to 0.039) compared with placebo (0.020 au, 95% CI 0.001 to 0.042).
CONCLUSIONS— An increase in the amount ofsubstrate for NOS increases the formation of endogenous NO.L-arginine may have therapeutic potential in diseases inwhich there is defective production of NO, but in asthma it may amplifythe inflammatory response in the airways.

     

左旋精氨酸恢复eNOS和iNOS平衡并抑制肺动脉高压的研究

目的 探讨诱导型一氧化氮合酶(iNOS)在中、晚期肺动脉高压(PH)发病中的作用机制及左旋精氨酸 (L-Arg)对其产生的影响.方法 30只雄性SD大鼠随机均分为5组,对照组(C组)、MCT3组(M3组)、MCT5组(M5组)、L-Arg3/MCT3组(L3组)、L-Arg5/MCT5组(L5组).除C组外其他组大鼠均用野百合碱一次性腹腔注射诱导PH模型.此后L3组和L5组分别连续每天腹腔注射L-Arg 3周和5周,M3组和M5组分别连续每天腹腔注射与L-Arg等量的生理盐水3周和5周,C组连续每天腹腔注射与L-Arg等量的生理盐水共5周.实验周期结束则用右心导管法测定右心室收缩压(RVSP),间接反映肺动脉压力,然后取大鼠肺组织做免疫组化,检测各组iNOS、内皮一氧化氮合酶(eNOS)和弹性蛋白(elastin)的表达变化.结果 M3和M5组中iNOS和elastin的表达明显高于C组,而eNOS表达明显少于C组;L3和L5组iNOS和elastin的表达少于相应M3和M5组,但L5组两种蛋白表达仍高于C组,L3和L5组eNOS的减少明显比相应M3和M5组少,但不及C组.结论 PH形成的中、晚期,肺组织中eNOS表达减少,而此时iNOS的表达增高可能产生大量一氧化氮(NO),但并没有改善PH的病情,而L-Arg能够恢复eNOS和iNOS之间的平衡并有效抑制PH的进展.     

Involvement of L-arginine/nitric oxide pathway at the paraventricular nucleus of hypothalamus in central neural regulation of penile erection in the rat

The objective of this study is to investigate whether the L-arginine/nitric oxide pathway is involved in the neurotransmission of paraventricular nucleus of hypothalamus (PVN) activation-induced penile erection in the rat. Male adult Sprague-Dawley rats anesthetized with pentobarbital were used. The femoral artery was cannulated to measure systemic and mean arterial pressure (SAP and MAP), and heart rate (HR). A 26-gauge needle was inserted into corpus cavernosum to measure the intracavernous pressure (ICP) simultaneously with SAP, MAP and HR on a polygraph. Four groups of study were arranged: (1) stereotaxically delivery of L-arginine (500 nmol/500 nl) into PVN; (2) administration of a mixture (1 microl) containing N(G)-Nitro-L-arginine methyl ester (L-NAME) 500 nmol and L-arginine 500 nmol into PVN; (3) microinjection of saline 500 nl into PVN as a vehicle control; and (4) intracavernous injection of L-arginine (100 nmol/50 microl). The ICP, SAP, MAP and HR were monitored for at least 2 h after each administration of the experimental agents. Upon administration of L-arginine into PVN, there was a significant increase of ICP from resting 9.6+/-2.5 mmHg to peaked at 64.4+/-9.8 mmHg after a latency of 3016.0+/-1749.7 s and with a duration of 27.6+/-15.8 min. There was no change of resting ICP after administration of the mixture of L-NAME and L-arginine into PVN. Application of saline to PVN and intracavernous injection of L-arginine failed to increase ICP. Based on elicitation of penile erection upon administration of L-arginine into PVN, and elimination of this L-arginine induced penile erection by co-administration of L-NAME with L-arginine, the results of this study suggest that L-arginine/nitric oxide pathway may be involved in the neurotransmission of PVN activation-induced penile erection in the rat.     

磷脂酰肌醇3激酶/蛋白激酶B通过上调内皮型一氧化氮合酶参与远端缺血后处理的脑保护作用

目的 探讨内皮型一氧化氮合酶(endothelial nitric oxide synthase,eNOS)及磷脂酰肌醇3激酶/蛋白激酶B(phosphoinositide-3 kinase/protein kinase B,PI3K/Akt)通路在远端缺血后处理(remote ischemic postconditioning,RIPoC)减少大鼠全脑缺血/再灌注(ischemia/repeffusion,I/R)损伤中的作用.方法 成年雄性SD大鼠100只,体重为200 g～250 g,按随机数字表法随机分为5组(每组20只):假手术组(S组)、缺血/冉灌注组(I/R组)、缺血/冉灌注+远端缺血后处理组(I/R+RIPoC组)、左旋硝基精氨酸甲酯( L-NAME)+缺血/再灌注+远端缺血后处理组(L-NAME+I/R+RIPoC组),以及LY294002+缺血/再灌注+远端缺血后处理组(LY+I/R+RIPoC组).采用四动脉阻断法建立大鼠全脑I/R模型.S组不制备全脑I/R模型；I/R+RIPoC组、L-NAME+I/R+RIPoC组及LY+I/R+RIPoC组于再灌注开始行双侧股动脉缺血15 min,再灌注15 min,共3个循环.L-NAME+I/R+RIPoC组于脑缺血前10 min腹腔注射非选择性一氧化氮合酶(nitric oxide synthase,NOS)抑制剂L-NAME,LY+I/R+RIPoC组于脑缺血前10 min侧脑室注射PI3K特异性抑制剂LY294002.脑再灌注48 h时行海马CA1区DNA原位末端缺口标记技术(terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling,TUNEL)阳性细胞计数,测定海马CA1区抗磷酸化的eNOS抗体(p-eNOS)、eNOS、p-Akt及Akt的蛋白水平,再灌注4d时行Morris水迷宫实验,再灌注7d时计算海马CA1区神经元密度.结果 与S组比较,I/R组、I/R+RIPoC组、L-NAME+I/R+RIPoC组及LY+I/R+RIPoC组再灌注时海马CA1区凋亡细胞[(0.8±0.8)、(84.7±6.8)、(52.8±7.8)、(74.3±9.0)、(79.5±7.3)个/mm]增加(P＜0.01),行为学损伤增加(P＜0.01),神经元密度[(193±7)、(10±7)、(91±11)、(38±7)、(26±7)个/mm]降低(P＜0.01).与I/R组比较,I/R+RIPoC组再灌注时凋亡细胞减少(P＜0.01),行为学损伤减少(P＜0.01),神经元密度增加(P＜0.01).与I/R+RIPoC组比较,L-NAME+I/R+RIPoC组及LY+I/R+RIPoC组再灌注时凋亡细胞增加(P＜0.01),行为学损伤增加(P＜0.01),神经元密度降低(P＜0.01).L-NAME能够抑制RIPoC后p-eNOS( 0.48±0.03、0.23 ±0.04)和eNOS (0.91±0.07、0.64±0.06)的升高(P＜0.01),LY294002不仅能抑制RIPoC后p-Akt (0.74±0.06、0.44±0.04)的升高(P＜0.01),而且能抑制RIPoC后p-eNOS( 0.48±0.03、0.23±0.04)和eNOS( 0.91±0.07、0.63±0.06)的升高(P＜0.01).结论 RIPoC能够减轻大鼠全脑I/R损伤,其作用机制与PI3K/Akt途径介导的eNOS激活和上调有关.     

The attenuation of hemorrhage-induced liver injury by exogenous nitric oxide, L-arginine, and inhibition of inducible nitric oxide synthase.

We investigated the role of nitric oxide (NO) in its ability to reduce liver injury in an animal model of hemorrhagic shock (HS). Ninety-six Sprague-Dawley rats weighing 250 to 300 g were divided in 6 groups (n = 16 per group) that included treatment at the beginning of resuscitation with normal saline (groups 1, 3) sodium nitroprusside (NP) (0.5 mg/kg) (groups 2, 4) L-arginine (300 mg/kg) (group 5), and L-N6-(1-iminoethyl) lysine (L-NIL, 40 mg/kg) (group 6). The experimental model of HS consisted of the withdrawal of 3 mL blood per 100 g in a 15-min period, tail amputation (75%), and drug administration at 30 min. This was followed by fluid resuscitation (FR) with lactated Ringer's (LR) solution to reach a mean arterial pressure (MAP) of 40 mm Hg, then a hospital phase of 60 min with hemostasis and FR with LR solution to reach a MAP of 70 mm Hg with a 3-day observation phase. NP, L-Arginine, and L-NIL significantly reduced fluid requirements for resuscitation (p =.0001) as well as significantly increased MAP after resuscitation from hemorrhage. We also observed an improved statistically significant difference (p =.001) in tests demonstrating less hepatic injury and histology damage. The mRNA expression of cytokines in the liver (interleukin [IL]-1alpha, IL-beta1, tumor necrosis factor [TNF]beta, IL-3, IL-4, IL-5, IL-6, IL-10, TNFalpha, IL-2, interferon [IFN]gamma) was reduced by NP treatment, L-arginine, and L-NIL. These data suggest that excess NO mediates hemorrhage-induced liver injury and that the suppression of inducible nitric oxide synthase (iNOS)-generated NO bioavailability with the NO donor sodium nitroprusside may reduce the pathophysiologic consequences of severe hemorrhage. This effect could be possibly related to the scavenging of to superoxide radicals (O2-) or the blockade of the deleterious effects of TNF and other inflammatory cytokines. The protective action noted with L-arginine cannot be fully explained within the context of this article, although it could be most likely associated with the supplementation of eNOS-generated NO.     

Pentoxifylline increases the level of nitric oxide produced by human spermatozoa

Pentoxifylline (PF) is a xanthine derivative drug primarily used to treat peripheral vascular disorders. It is currently used in assisted reproductive technologies to enhance human sperm motility. However, the mechanism by which this enhancement occurs is not fully understood. Given that nitric oxide has been identified as a trigger to sperm motion, we asked whether nitric oxide modulates the stimulatory effect of PF on sperm motility. A total of 41 semen samples from infertile males were studied. Nitric oxide production in the presence of 5 mm PF was tested using different bio‐analytical methods (spectrophotometry, fluorometry and fluorescence microscopy). The spectrophotometric determination showed higher levels of nitrite, an indirect measure for nitric oxide, in sperm samples supplemented with PF compared to controls. The fluorometric experiment showed higher 4, 5‐diaminofluorescein triazole, a product from the reaction between nitric oxide and 4, 5‐diaminofluorescein diacetate, after adding PF to spermatozoa. The fluorescence microscopy images of the spermatozoa supplemented with PF showed higher green fluorescence, indicating higher 4, 5‐diaminofluorescein triazole levels, compared to controls. It is concluded that PF enhances nitric oxide production in human spermatozoa, which explains, at least in part, the mechanism by which PF stimulates human sperm motility.     

Role of nitric oxide in urinary bladder function: effect of L-arginine

BACKGROUND: Evidence indicates that decreased blood flow to the bladder plays a major role in obstructive bladder dysfunction in the rabbit model of partial bladder outlet obstruction (PBOO), and that nitric oxide (NO) regulation of blood flow may be important in modulating the degree of obstructive bladder dysfunction. The specific aim of our study is to determine the effect of feeding rabbits a diet high in L-arginine on the response to PBOO. MATERIALS AND METHODS: Sixteen male NZ White rabbits were separated into 4 groups of 4 each. The rabbits in groups 1 and 3 underwent PBOO. The rabbits in groups 2 and 4 were sham-operated. For 1 week prior to surgery, and 2 weeks postoperatively, each rabbit in groups 1 and 2 was put on a diet containing 7% arginine. Rabbits in groups 3 and 4 were on a normal diet (0.76% arginine). RESULTS: PBOO resulted in a greater increase in bladder weight in the control group than the arginine group. PBOO resulted in a greater decrease in compliance in the control group than the arginine group. The contractile responses to all agents in the arginine control group were greater than in the control normal diet group. PBOO resulted in a greater decrease in the response to field stimulation in the control group than in the arginine group. CONCLUSIONS: These studies clearly demonstrate that feeding rabbits a diet high in L-arginine was beneficial for the control rabbits, and reduced the level of dysfunctions following PBOO.     

L-精氨酸对危重病人一氧化氮内毒素及免疫功能的影响

目的　探讨L 精氨酸对危重病人一氧化氮 (NO)、内毒素以及免疫功能的影响。方法　采用比色法、鲎试验改良基质显色法和流式细胞仪 ,在L 精氨酸输注前和输注 5d后分别对重症监护室(ICU) 12例危重病人外周血NO、内毒素浓度和免疫功能进行监测。结果　低于正常范围的NO-2 /NO-3 在给予L 精氨酸以后上升至正常范围 ,从 (5 6 .36± 2 6 .0 1) μmol升至 (74.31± 2 1.89) μmol。给药后内毒素、CD3、CD4均下降 ,而CD8、CD19、C16 /CD5 6、T B NK下降 ,但均无统计学意义。结论　在危重状况下 ,L 精氨酸影响NO的生成 ,与内毒素呈反向关系 ,对T细胞免疫有下调作用。     

Endothelium-dependent vasodilatation is impaired in both microcirculation and macrocirculation during acute hyperglycemia

Purpose: Endothelial dysfunction is associated with atheromatosis and is a common finding with diabetes. We have studied the effects of acute hyperglycemia on the endothelium-dependent vasodilatation of both the microcirculation and the macrocirculation of healthy subjects. Because of the presence of endothelial dysfunction with diabetes, we hypothesize that acute hyperglycemia causes impaired endothelial-dependent responses. Methods: Twenty healthy subjects (15 men, 5 women) with a mean age of 32.3 years (range, 23 to 49 years) were examined during fasting conditions and at 1 hour after the ingestion of 75 g of glucose. The endothelium-dependent vasodilatation of the brachial artery, a conduit vessel, was evaluated with high-resolution ultrasound scan to measure the changes in the vessel diameter induced with reactive hyperemia. In the microcirculation, the endothelial function was assessed by measuring the changes in the erythrocyte flux after the acetylcholine iontophoresis. Results: The brachial artery endothelium-dependent dilatation was greater during fasting as compared with the response after the glucose load was administered (11.7% [8.3 to 14.3] vs 4.2% [1.5 to 9.6]; P < .001; median, first, and third quartile). Both peak and average blood flow velocities during the hyperemic response were higher after the administration of the glucose load as compared with the fasting period (P < .05), but no changes were found in the blood flow volume. During fasting, microcirculatory endothelial-dependent vasodilatation was also significantly greater than the response after the administration of the glucose load (1293% [591 to 1856] vs 863% [385 to 1180]; P < .01). Conclusions: In healthy subjects, the ingestion of a glucose load impairs the endothelial-dependent vasodilation in both the microcirculation and the macrocirculation. Because impairment of endothelial responses is associated with the early changes of atherosclerosis, it is possible that prolonged hyperglycemia and endothelial dysfunction may lead to the early and accelerated atherosclerosis of diabetes. Further studies are necessary to examine the long-term effects of hyperglycemia. (J Vasc Surg 1998;28:687-94.)     

Dose dependency of L-arginine in neonatal myocardial protection: the nitric oxide paradox.

OBJECTIVES: Recent experimental studies have suggested that enriching cardioplegic solution with L-arginine improves myocardial protection by increasing nitric oxide production. Nitric oxide, however, also generates the toxic oxygen-derived free radical peroxynitrite; thus these beneficial effects may be dose dependent, especially in vulnerable (stressed) hearts. METHODS: Fifteen neonatal piglets underwent 60 minutes of ventilator hypoxia (inspired oxygen fraction 8%-10%) followed by 20 minutes of normothermic ischemia on cardiopulmonary bypass (stress). They were then protected for 70 minutes with multiple doses of blood cardioplegic solution. In 5 (group 1), the cardioplegic solution contained no L-arginine, in 5 (group 2), it was enriched with a 4 mmol/L concentration of L-arginine, and in 5 (group 3), a 10 mmol/L concentration of L-arginine. Myocardial function was assessed by means of pressure volume loops and expressed as a percentage of control, and coronary vascular resistance and conjugated diene production were measured during infusions of cardioplegic solution. RESULTS: Compared with the protection afforded by blood cardioplegic solution without L-arginine (group 1), the addition of a 4 mmol/L concentration of L-arginine (group 2) significantly improved myocardial protection, resulting in complete return of systolic function (end-systolic elastance 38% vs 100%; P <.001 vs 4 mmol/L L-arginine) and preload recruitable stroke work (40% vs 100%; P <. 001 vs 4 mmol/L L-arginine); minimal increase in diastolic stiffness (239% vs 158%; P <.001 vs 4 mmol/L L-arginine); and lower coronary vascular resistance, conjugated diene production, and myeloperoxidase activity (P <.001 vs 4 mmol/L L-arginine in each case). Conversely, supplementing the cardioplegic solution with a 10 mmol/L dose of L-arginine (group 3) negated these beneficial effects, resulting in depressed systolic function (end-systolic elastance 41% +/- 2%; P <.001 vs 4 mmol/L L-arginine) and preload recruitable stroke work (40% +/- 2%; P <.001 vs 4 mmol/L L-arginine); increased diastolic stiffness (246% +/- 7%; P <.001 vs 4 mmol/L L-arginine); and higher conjugated diene production, myeloperoxidase activity, and coronary vascular resistance (P <.001 vs 4 mmol/L L-arginine in each case). CONCLUSIONS: Enriching cardioplegic solution with a 4 mmol/L concentration of L-arginine significantly improves myocardial protection by reducing oxygen-derived free radical formation by white blood cells, thus preserving vascular and myocardial function. However, these beneficial effects are dose dependent because 10 mmol/L concentrations of L-arginine increase oxygen-derived free radical production, resulting in vascular and myocardial dysfunction.     

Therapeutic approach against intimal hyperplasia of vein grafts through endothelial nitric oxide synthase/nitric oxide (eNOS/NO) and the Rho/Rho-kinase pathway

Late graft failure of autologous vein grafts is associated with intimal hyperplasia resulting from the migration and proliferation of vascular smooth muscle cells (VSMCs). Endothelial nitric oxide synthase (eNOS) is an enzyme that synthesizes nitric oxide (NO). An impairment of NO-mediated vasorelaxation and increases in cell proliferation occurs in vein grafts after the surgery and these pathophysiological changes cause intimal thickening. The Rho/Rho-kinase pathway negatively regulates eNOS and is involved in intimal hyperplasia. Several studies have been conducted with the goal of controlling intimal hyperplasia targeting eNOS/NO and the Rho/Rho-kinase pathway. The oral administration of drugs, such as Rho-kinase inhibitor, l-arginine, beta-blocker and statins, significantly suppressed intimal thickening in animal models. This study revealed that statins upregulate eNOS through Rho-kinase inhibition to suppress intimal hyperplasia. The intraluminal gene transfer of eNOS inhibited intimal hyperplasia, thereby reducing the cell proliferation. These approaches are thus considered to be potentially promising therapeutic modalities for graft failure.     

A comparison of the vasodilatation produced by two topical anaesthetics

The vasoactive properties of EMLA (eutectic mixture of local anaesthetic) and amethocaine were compared using Doppler colour ultrasound to measure vein diameter in 20 male volunteers. EMLA or amethocaine cream were applied over veins on the dorsum of the hand and vein diameter was measured prior to application of the preparations and at 1, 1.5 and 2 h after removal. Visual analogue scores for skin colour and vasodilatation were performed at 1 h. The results showed no significant difference in vein diameter between the EMLA and amethocaine groups. However, the amethocaine-treated hands were significantly more erythematous at 1 h (p < 0.00002).     

Reduction in [D-Ala2, NMePhe4, Gly-ol5]enkephalin-induced peripheral antinociception in diabetic rats: the role of the L-arginine/nitric oxide/cyclic guanosine monophosphate pathway

To test our hypothesis that the abnormally small efficacy of mu-opioid agonists in diabetic rats may be due to functional changes in the L-arginine/nitric oxide (NO)/cyclic guanosine monophosphate (cGMP) pathway, we evaluated the effects of N-iminoethyl-L-ornithine, methylene blue, and 3-morpholino-sydnonimine on [D-Ala(2), NMePhe(4), Gly-ol(5)]enkephalin (DAMGO)-induced antinociception in both streptozotocin (STZ)-diabetic and nondiabetic rats. Animals were rendered diabetic by an injection of STZ (60 mg/kg intraperitoneally). Antinociception was evaluated by the formalin test. The mu-opioid receptor agonist DAMGO (1 microg per paw) suppressed the agitation response in the second phase. The antinociceptive effect of DAMGO in STZ-diabetic rats was significantly less than in nondiabetic rats. N-Iminoethyl-L-ornithine (100 microg per paw), an NO synthase inhibitor, or methylene blue (500 microg per paw), a guanylyl cyclase inhibitor, significantly decreased DAMGO-induced antinociception in both diabetic and nondiabetic rats. Furthermore, 3-morpholino-sydnonimine (200 microg per paw), an NO donor, enhanced the antinociceptive effect of DAMGO in nondiabetic rats but did not change in diabetic rats. These results suggest that the peripheral antinociceptive effect of DAMGO may result from activation of the L-arginine/NO/cGMP pathway and dysfunction of this pathway; also, events that are followed by cGMP activation may have contributed to the demonstrated poor antinociceptive response of diabetic rats to mu-opioid agonists. IMPLICATIONS: This is the first study on the role of the nitric oxide (NO)/cyclic guanosine monophosphate pathway on [D-Ala(2), NMePhe(4), Gly-ol(5)]enkephalin (DAMGO)-induced peripheral antinociception and the effect of diabetes on this pathway. The study suggests a possible role of DAMGO as a peripherally-acting analgesic drug.     

左旋精氨酸对不对称二甲基精氨酸与一氧化氮水平的影响

目的 观察先天性心脏病合并中、重度肺动脉高压(PAH)行心内直视修补术患者静滴左旋精氨酸(L-Arg)对不对称二甲基精氨酸(ADMA)和一氧化氮(NO)水平的影响.方法 20例入院时肺动脉收缩压(PASP)＞50 mm Hg拟在心肺转流(CPB)下行心内修补术患者,随机分为L-Arg治疗组(Ⅰ组)和对照组(Ⅱ组),每组10例.Ⅰ组术前加用L-Arg静滴;Ⅱ组术前接受常规治疗.所有患者在治疗前(T1)、麻醉诱导前(T2)、停CPB时(T3)、CPB结束后12 h(T4)、24 h(T5)及72 h(T5)各采集桡动脉血,测定ADMA和NO的浓度.治疗前、术前、术后第1天及第3天各测一次PASP.结果 Ⅰ组和Ⅱ组T1时NO、ADMA及PASP差异无统计学意义.与T1时比较,Ⅰ组T2、T4～T6时NO浓度升高、T2～T6时ADMA浓度降低(P＜0.05);Ⅱ组T3～T6时NO浓度降低、T4～T6时Ⅰ组ADMA浓度明显升高(P＜0.05).T2、T4～T6时Ⅰ组NO浓度高于Ⅱ组、ADMA浓度低于Ⅱ组(P＜0.05);Ⅰ组PASP术前、术后第1天、第3天均低于Ⅱ组(P＜0.05).结论 CPB可致ADMA浓度增高、NO浓度降低.静注L-Arg可提高NO的浓度,降低ADMA浓度,而且对降低PAH患者行心内修补术后肺动脉压力有积极意义.     

Polymorphisms in the endothelial nitric oxide synthase gene and bone density/ultrasound and geometry in humans

Nitric oxide (NO), produced by endothelial cells, is a signaling molecule synthesized from l-arginine by nitric oxide synthases (NOS). NO is known to reduce the ratio of receptor activator of nuclear factor KappaB (RANKL)/osteoprotegerin (OPG), leading to decreased osteoclastogenesis and a reduction in bone resorption. Endothelial nitric oxide synthase (eNOS or NOS3) is the predominant constitutive isoform of nitric NOS within bone. Recently, a NOS3 polymorphism, Glu298Asp, previously implicated in osteoporosis, failed to demonstrate an association with bone mineral density (BMD), although there was some indication of an association with selected geometry indices. Since a single polymorphism does not capture all of the potential variants in a given gene, we investigated a broader coverage of the NOS3 gene with bone density/ultrasound and geometry indices in a sample of unrelated individuals from the Framingham Offspring Study. Our results indicated that the Glu298Asp polymorphism was not associated with BMD but suggested some haplotype-based associations in the linkage disequilibrium (LD) region that included the Glu298Asp polymorphism with several geometry indices. Although our findings exhibited several associations with selected bone density/ultrasound and geometry indices, the nominally significant associations are regarded as primarily hypothesis generating and suggest that replication in other samples is needed. Thus, NOS3 genetic variation does not appear to be a major contributor to adult bone density/ultrasound and geometry in our sample.     

L-arginine, the substrate of nitric oxide synthase, inhibits fertility of male rats

Aim: To examine the effect of L-arginine, the substrate of nitric oxide (NO) synthase, on reproductive function ofmale rats. Methods: Male rats were gavaged with either L-arginine (100 or 200 mg·kg~(-1)·d~(-1)), D-arginine (200mg·kg~(-1)·d~(-1)) or vehicle (0.9% NaCl) for seven consecutive days. Their sexual behaviour and fertility were evaluat-ed using receptive females. Results: L-arginine (200 mg/kg) had no significant effect on sexual competence (interms of sexual arousal, libido, sexual vigour and sexual performance). In mating experiments, the higher dose of L-arginine effectively and reversibly inhibited fertility, whilst the lower dose and the inactive stereoisomer D-arginine hadno significant effect. The antifertility effect caused by L-arginine was due to a profound elevation in the preimplantationloss mediated possibly by impairment in epididymal sperm maturation, hyperactivated sperm motility and sperm capaci-tation. Conclusion: Elevated NO production may be detrimental to male fertility