Effect of exogenous angiotensin II on renal tissue nitric oxide and intrarenal circulation in anaesthetized rats

AIM: The renal medullary circulation is protected against depressor action of angiotensin II (Ang II) because of the opposed action of a vasodilator agent, possibly nitric oxide (NO). This possibility was evaluated by a simultaneous determination of the effect of exogenous Ang II on renal cortical and medullary tissue NO and on intrarenal circulation. METHODS: In anaesthetized rats effects were determined of pressor and subpressor Ang II doses on tissue NO concentration in the renal cortex and inner medulla (selective NO electrodes), total renal blood flow (RBF, Transonic renal artery probe) and inner medullary blood flow (IMBF, laser Doppler flux). The measurements were repeated in rats treated with tempol, a scavenger of superoxide. RESULTS: Moderately pressor Ang II infusion significantly decreased tissue NO signal from 5.7 +/- 0.2 to 5.3 +/- 0.2 nA in the cortex and from 10.7 +/- 0.6 to 10.1 +/- 0.6 nA in the medulla. The RBF, a measure of cortical perfusion, decreased, and IMBF did not change. Subpressor doses of Ang II did not change medullary or cortical tissue NO. Tempol prevented an Ang II dependent decrease in medullary (but not cortical) NO without affecting RBF or IMBF responses. CONCLUSION: An absence of an increase in renal cortical or medullary tissue NO after infusion of subpressor or pressor doses of Ang II speaks against the role of this agent in buffering the intrarenal vasoconstrictor action of the hormone. Elimination of the post-Ang II decrease in medullary NO in animals pre-treated with tempol suggests that tissue superoxide generation stimulated by the hormone might reduce local bioavailability of NO.     

Neuronal nitric oxide synthase and splanchnic blood flow in anaesthetized rats

AIMS: To evaluate to what extent the neuronal form of constitutive nitric oxide synthase (nNOS) contributes to the blood perfusion of splanchnic organs, including the islets of Langerhans. METHODS: The nNOS inhibitor 7-nitroindazole (300 mg kg(-1) i.p.) was administered to anaesthetized Sprague-Dawley rats, some of which were pre-treated with the ganglionic blocker hexamethonium (20 mg kg(-1) i.v.) The blood perfusion of the splanchnic organs, including the pancreatic islets was then measured with a microsphere technique. RESULTS: Nitroindazole decreased total pancreatic, duodenal and renal blood flow, whereas pancreatic islet, colonic and adrenal blood flows were unchanged. A slight increase in mean arterial blood pressure was seen after nitroindazole treatment. Nitroindazole did not affect blood glucose or serum insulin concentrations. In separate experiments, hexamethonium affected none of the studied blood flow values, suggesting that the effects of nNOS-inhibition were not mediated from the nervous system. CONCLUSION: Nitric oxide derived from the activity of nNOS contributes to the blood perfusion in the upper portions of the gastrointestinal tract, viz. the parts supplied by the cranial mesenteric artery, and the kidneys, whilst no effects are seen on colonic or adrenal blood flow. Pancreatic islet blood flow was unaffected by nNOS inhibition, thereby suggesting that NO derived from the other isoforms of NOS maintains the high basal islet blood perfusion.     

Decreased renal haemodynamic response to inhibition of nitric oxide synthase in subtotally nephrectomized rats

To assess the renal haemodynamic response to manipulations of the nitric oxide (NO) system, we examined subtotally nephrectomized (SNX) rats and control rats (CON) 28 days after their operation. Bolus infusions of the NO synthase inhibitor N ^G-nitro-l-arginine (l-NA) were given intravenously at doses of 2 mg/kg and 10 mg/kg. Blood pressure was measured intra-arterially, glomerular filtration rate was measured by inulin clearance and fractional changes in renal blood flow (RBF) were determined by a Doppler flow probe. Both doses of l-NA caused a similar and dose dependent increase in mean blood pressure in both SNX and CON rats. In contrast, the decrease in RBF and the increase in the renovascular resistance index (RVRI) was less in SNX rats as compared to CON rats (RBF = –70.1±2.2% of baseline vs –52.7±5.2%, P<0.01; RVRI = +177±9% of baseline vs +243±24%, P<0.05). These changes were not affected by autonomic blockade (hexamethonium), or by blockade of the angiotensin II receptor (Losartan). The exogenous NO donor sodium nitroprusside (0.5 and 1.5 g · kg^–1 · min^–1) lowered mean blood pressure to a similar degree in SNX and CON rats; in contrast, RVRI decreased less in SNX rats (86.9±9.2% of baseline) than in CON rats (68.2±4.6%, P<0.05). We conclude that the reaction of the renal vasculature to manipulations of the NO system is altered in the SNX rats. The data suggest that in the remnant kidney, renovascular resistance is less dependent on endogenous NO and the vascular bed is less sensitive to exogenous NO.     

Effect on renin release of inhibiting renal nitric oxide synthesis in anaesthetized dogs

Nitric oxide plays an important role in the regulation of basal renal blood flow. This study was performed to examine whether selective inhibiti± of renal nitric oxide synthesis affects renin release in vivo. Accordingly, in six barbiturate-anaesthetized dogs renin release was examined before and after intrarenal infusion of the selective inhibitor of nitric oxide synthesis, N^G-nitro-l -arginine (NOARG). NOARG was infused into the renal artery to yield a renal arterial blood concentration of 0.4 μmol ml^-1. NOARG did not change systemic arterial blood pressure and glomerular filtration rate, but reduced basal renal blood flow by 26 ± 2%. Urine flow, sodium and potassium excretion were reduced after inhibition of renal nitric oxide synthesis. Basal renin release (3 ± 2 μg AI min^-1) was not altered by NOARG infusion (1 ± 1 μg AI min^-1). To stimulate renin release the renal artery was constricted to a renal perfusion pressure of 50 mmHg. At this perfusion pressure infusion of NOARG reduced renin release significantly from 48 ± 11 μg AI min^-1to 14 ± 4 μg AI min^-1. In conclusion, inhibition of renal nitric oxide synthesis reduces basal renal blood flow and reduces renin release stimulated by renal arterial constriction. These findings indicate that renal nitric oxide modulates both renal blood flow and renin release in vivo.     

Melatonin attenuates renal ischemia-reperfusion injury in nitric oxide synthase inhibited rats

Recent studies show that melatonin reduces the blood pressure (BP) and ischemia/reperfusion (I/R)-induced damage. This study was designed to investigate the effects of melatonin on the renal I/R injury in rats given the nitric oxide synthase (NOS) inhibitor, N(omega)-nitro-L-arginine methyl ester (L-NAME). After right nephrectomy, I/R was induced by occlusion of the left renal vessels for 60 min, followed by 24h reperfusion. The administration of melatonin significantly attenuated BP in NOS-inhibited hypertensive rats. Malondialdehyde (MDA) levels, a stable metabolite of the free-radical-mediated lipid peroxidation cascade, were found to be significantly higher in the I/R group (3.48+/-0.2mg/l serum) than in the control group (2.69+/-0.2mg/l serum). L-NAME (40 mgkg(-1) for 15 days)+I/R significantly increased the MDA levels compared to I/R alone. Melatonin administration to L-NAME rats significantly reduced the MDA values resulting from I/R. We also demonstrated that I/R, and especially L-NAME+I/R, lead to structural changes in the kidney and that melatonin attenuates these changes. These results suggest that melatonin reduces BP and I/R injury in NOS inhibited rats by L-NAME.     

The expression and activity of renal nitric oxide synthase and circulating nitric oxide in polycystic kidney disease rats

Nitric oxide (NO) influences tubular fluid and electrolyte transport, and hence possibly also fluid accumulation in renal cysts. The expression and activity of intrarenal constitutive NO synthase (cNOS) [neuronal NOS, nNOS and endothelial NOS, eNOS] and inducible NOS (iNOS) and plasma nitrite/nitrate (PNOx) concentration were assessed in homozygous Han:SPRD polycystic kidney disease (PKD) rats (cy/cy), heterozygous Han:SPRD PKD rats (cy/+), homozygous normal Han:SPRD littermates (+/+) and Sprague Dawley rats (sd). The results showed: 1) nNOS expression was decreased in proximal tubules and thick ascending limbs of the loop of Henle in cy/cy and cy/+ rats compared to +/+ and sd rats (p<0.05). nNOS was weakly expressed in the epithelium of small cysts and unexpressed in epithelium of large cysts. 2) iNOS expression was increased in proximal tubular epithelial cells in cy/+ rats compared to +/+ rats and sd rats (p<0.01). iNOS expression in cyst epithelium was decreased in cy/+ rats (p<0.05) and absent in cy/cy rats. 3) eNOS expression was similar in the endothelium of intrarenal arteries in all groups. 4) The activity of renal cNOS was decreased in cy/cy and cy/+ rats; the activity of iNOS was decreased only in cy/cy rats, with no significant difference among the other three groups. 5) PNOx concentration was higher in cy/cy rats than in the other three groups, and correlated positively with plasma creatinine and urea. In conclusion, NOS expression and activity decreased as cysts developed, suggesting that NO downregulation is involved in the pathogenesis of PKD.     

The inhibition of nitric oxide synthase suppresses LPS- and psychological-stress-induced fever in rats

The purpose of this study was to assess the effects of a non-selective nitric oxide synthase (NOS) inhibitor on changes in fever response due to injection of lipopolysaccharide (LPS) or on stress fever caused by exposure to an open field in freely moving biotelemetered rats. N(omega)-nitro-L-arginine methyl ester (L-NAME), an inhibitor of all NOS-isoforms, was injected intraperitoneally (ip) at a dose of 50 mg/kg just before intraperitoneal injection of LPS at a dose of 50 microg/kg or exposure to open field. L-NAME at a dose of 50 mg/kg had no effect on normal day-time body temperature (T(b)) and normal night-time T(b). The same dose of L-NAME administered intraperitoneally caused a significant attenuation of LPS-induced fever. The thermal index calculated for rats pretreated with L-NAME and injected with LPS was reduced by approximately 75% compared to that calculated for saline-pretreated and LPS-injected rats. To examine the effect of NOS inhibition on psychological-stress-induced elevation in T(b), rats were injected intraperitoneally with L-NAME and then immediately exposed to open field for 60 min. After exposure to the open field, rats not treated with NOS inhibitor responded with a rapid rise in T(b), and it was accompanied with an increase of motor activity. L-NAME significantly suppressed the stress fever without any effect on changes in motor activity. Presented data provide clear evidence that NO formation is involved in LPS- and psychological-stress-induced fevers in rats.     

Different responses of nitric oxide synthase inhibition on morphine-induced antinociception in male and female rats

The roles of gonadal hormones and nitric oxide on pain perception and their interaction have been widely investigated. In the present study the chronic effect of l-NAME (NOS inhibitor) on morphine-induced antinociception in male and female rats was investigated. Forty rats were divided into four groups: (1) female (2) female-LN (3) male (4) and male-LN. The animals of groups 2 and 4 received daily injection of l-NAME (10 mg/kg) during 3 weeks. The animals of control groups 1 and 3 received 2 ml/kg saline instead of l-NAME. Finally, all animals were tested on the hot plate test (52 ± 0.2 °C; Cut-off 80 s) to evaluate the antinociceptive effects of morphine. The hot plate test was performed for base record 15 min before the injection of morphine (10 mg/kg; s.c.) and consequently it was repeated every 15 min after the injection. There were no significant differences in baseline latencies among all groups. Reaction times after injection of morphine in female-LN were higher than in the female control group (p < 0.01). There was, however, no significant difference between male control and male-LN groups. Reaction times in the female-LN group were significantly higher than in the male-LN group. Reaction times after injection of morphine in the male group was longer than in the female group (p < 0.01). It is concluded that sex hormones such as testosterone and estrogen have a role in pain perception and analgesia. NO has a modulatory effects on functions of sex hormones in pain perception and analgesic effects of opioids.     

诱导型一氧化氮合酶对大鼠胰岛细胞凋亡的影响

目的:探讨细胞因子和诱导型一氧化氮合酶(iN-OS)对体外培养的大鼠胰岛细胞凋亡和功能的影响及其机制。方法:大鼠胰岛细胞体外培养,随机分组,培养液中分别加入细胞因子IL-1β、TNF-α和/或iNOS抑制剂氨基胍,分为空白对照组、细胞因子组、氨基胍组、氨基胍+细胞因子组。检测指标包括:培养液NO水平和组织iNOS、结构型NOS活性,RT-PCR检测胰岛组织中iNOS基因和凋亡相关基因Bax、Bcl-2的表达情况,AO/EB染色检测胰岛存活,胰岛素释放实验检测胰岛功能。结果:与细胞因子IL-1β和TNF-α共同培养后,大鼠胰岛组织中iNOS的表达增强,活性显著提高(38.93±4.72)U/mL,NO水平上升(313.0±35.4)mol/L,而结构型NOS没有变化;同时胰岛促凋亡基因表达上调,抗凋亡基因表达下降,细胞的存活率下降,胰岛素分泌大大减少。加入氨基胍后,随着胰岛组织中iNOS的活性明显受到抑制,胰岛的凋亡程度减轻,存活和胰岛素分泌情况都明显改善。结论:iNOS在细胞因子诱导的胰岛细胞凋亡中起到十分关键的作用,而氨基胍通过抑制iNOS活性,减轻了细胞因子的损害,降低了胰岛凋亡水平,改善胰岛的存活与功能。     

Effect of focal cerebral ischemia on nitric oxide synthase expression in rats

Time- and cell-type-dependent immunohistochemical activity of nitric oxide synthase (NOS) was investigated in rat cerebral cortex following focal ischemia and the local concentration of nitric oxide (NO) was measured. NO concentration increased 2 min after the ischemia. Brain NOS-immunoreactive neurons increased in number 5 min after the ischemia. Endothelial cell NOS immunoreactivity was first detected in vascular endothelial cells and astrocytes 5 min after the ischemia, and it increased again during 60 min to 4 days after the ischemia in reactive astrocytes. Inducible NOS immunoreactivity was detected in astrocytes, vascular endothelium, and microglia/macrophages at the periphery of the ischemic core during 2–4 days after the ischemia.This study was presented at the 28th Annual Meeting of the Clinical Electron Microscopy Society of Japan, Osaka, October 17–19, 1996.     

小肠内NOS分布及NO作用研究进展

一氧化氮作为一种细胞间和细胞内的信息物质 ,在小肠的生理病理过程中有重要作用。本文着重介绍小肠内的一氧化氮合酶分布NO与小肠运动、消化吸收、粘膜保护的关系等方面的研究进展。     

吸烟大鼠一氧化氮合酶和一氧化氮的变化

目的:观察吸烟对大鼠肺组织iNOS、eNOSmRNA和蛋白表达以及支气管肺泡灌洗液(BALF)中NO的影响, 探讨不同类型的NOS在吸烟所致慢性气道炎症中的作用。方法:选用Wistar大鼠80只随机分为对照组, 被动吸烟组, iNOS抑制剂L-NIL干预组及NOS抑制剂L-NAME干预组。用免疫组化法检测iNOS及eNOS的蛋白表达, 用RT-PCR检测iNOS及eNOSmRNA的表达, 用Griess法测定BALF中的NO^-₂/NO^-₃含量。结果:吸烟大鼠肺组织中iNOSmRNA及其蛋白表达增加, eNOSmRNA及蛋白表达下降, BALF中细胞总数及NO^-₂/NO^-₃显著增加(P＜0.05)。在体实验发现, L-NIL使BALF中细胞总数及NO^-₂/NO^-₃下降(P＜0.05);L-NAME对BALF中细胞总数及NO^-₂/NO^-₃无显著影响(P＞0.05)。结论:吸烟大鼠肺组织iNOSmRNA和蛋白表达增加, eNOSmRNA和蛋白表达减少。活化的iNOS产生大量NO促进炎症发展。     

Sperm nitric oxide and motility: the effects of nitric oxide synthase stimulation and inhibition

Nitric oxide (NO) is synthesized from L-arginine by a family of enzymes known as the nitric oxide synthases (NOS). We have recently shown a NOS similar to constitutive brain NOS (bNOS) and endothelial NOS (ecNOS) to be present in spermatozoa. The aim of this study is to investigate NO production by human spermatozoa and the effects of stimulation and inhibition of NOS. This was carried out using the Iso-NO, an isolated NO meter and sensor, which provides rapid, accurate and direct measurements of NO. Semen samples with normozoospermic and asthenozoospermic profiles were prepared using a direct swim-up technique. Basal concentrations of NO and stimulated NO production were measured after exposure to the calcium ionophore (A23187; 0.01-10 microM) a potent activator of constitutive NOS. NO production in human spermatozoa was significantly increased by the addition of A23187 30 seconds after stimulation. Furthermore, this response was greatly diminished by pre-incubating the samples with competitive inhibitors of L-arginine, the substrate for NOS, before treatment with calcium ionophore. In the presence of N(G)-nitro-L-arginine methyl ester (L- NAME), N(G)-nitro-L-arginine (L-NA) or N(G)-methyl-L-arginine (L-NMMA; all at 10 microM), NO production was inhibited with a rank order of potency L-NAME > L-NMMA > L-NA which is in accordance with the inhibition of an endothelial type of constitutive NOS.      

Central nitric oxide synthase inhibition restores behaviorally mediated lipopolysaccharide induced fever in near-term rats

It has recently been established that the febrile response to bacterial endotoxin attenuated late in pregnancy is partially restored by central inhibition of nitric oxide synthase (NOS). To determine if this restoration of the febrile response also extends to warm-seeking behavior, we used a thermocline to allow animals to select their preferred ambient temperature. Near-term pregnant (day 19-20) and aged matched non-pregnant rats were given an i.p. injection of lipopolysaccharide (LPS, 50 microg/kg) and an intracerebroventricular (i.c.v.) injection of an inhibitor of NOS, N(G)-monomethyl-L-arginine acetate salt (L-NMMA, 100 microg) or vehicle. Core body temperature and self-selected ambient temperature were measured for 6 h after injection. Inhibition of brain NOS before LPS injection resulted in a significant febrile response with an associated increase in selected ambient temperature in both near-term and non-pregnant animals. As expected, near-term dams that received i.c.v. vehicle + i.p. LPS did not have a febrile response but displayed a small hypothermic reaction with no change in selected ambient temperature. We conclude that blockade of brain NOS restores maternal hyperthermic and warm-seeking responses to LPS in near-term pregnancy.     

Effects of nitric oxide synthase inhibition on vascular conductance during high speed treadmill exercise in rats

To determine the functional role of nitric oxide (NO) in regulating vascular conductance during high intensity dynamic exercise in skeletal muscles composed of all major fibre types, female Wistar rats (277 +/- 4 g; n = 7) were run on a motor-driven treadmill at a speed and gradient (60 m min(-1), 10 % gradient) established to yield maximal oxygen uptake (V(O2,max)). Vascular conductance (ml min(-1) (100 g)(-1) mmHg(-1)), defined as blood flow normalised to mean arterial pressure (MAP), was determined using radiolabelled microspheres during exercise before and after NO synthase (NOS) inhibition with N (G)-nitro-L-arginine methyl ester (L-NAME; 10 mg kg(-1), I.A.). The administration of L-NAME increased MAP from pre-L-NAME baseline values, demonstrating that NOS activity is reduced. The administration of L-NAME also reduced vascular conductance in 20 of the 28 individual hindlimb muscles or muscle parts examined during high speed treadmill exercise. These reductions in vascular conductance correlated linearly with the estimated sum of the percentage of slow twitch oxidative (SO) and fast twitch oxidative glycolytic (FOG) types of fibres in each muscle (Deltaconductance = -0.0082(%SO + %FOG) - 0.0105; r = 0.66; P < 0.001). However, if the reduction in vascular conductance found in the individual hindquarter muscles or muscle parts was expressed as a percentage decrease from the pre-L-NAME value (%Delta = (pre-L-NAME conductance - post-L-NAME conductance)/ pre-L-NAME conductance x 100), then the reduction in vascular conductance was similar in all muscles examined (average %Delta = -23 +/- 2 %). These results suggest that NO contributes substantially to the regulation of vascular conductance within and among muscles of the rat hindquarter during high intensity exercise. When expressed in absolute terms, the results suggest that the contribution of NO to the regulation of vascular conductance during high intensity exercise is greater in muscles that possess a high oxidative capacity. In contrast, if results are expressed in relative terms, then the contribution of NO to the regulation of vascular conductance during high intensity exercise is similar across the different locomotor muscles located in the rat hindlimb and independent of the fibre type composition.     

一氧化氮对肾性高血压大鼠主动脉收缩功能的影响

目的:探讨二肾一夹（2K1C）肾性高血压大鼠主动脉收缩功能的改变及其与一氧化氮的关系。 方法:实验分为假手术组、2K1C组、卡托普利组、NAME组和精氨酸组等5组，利用术后4周的肾性高血压大鼠的胸主动脉进行离体血管环实验，并测定主动脉环一磷酸鸟苷（cGMP）的含量。 结果:2K1C肾性高血压大鼠离体主动脉环对苯肾上腺素、血管紧张素Ⅱ、ACh、KCl的收缩反应显著高于假手术组，主动脉cGMP含量明显少于假手术组。卡托普利可逆转2K1C大鼠的上述改变。L-精氨酸可使上述异常的主动脉收缩功能部分恢复，并增加主动脉cGMP含量。一氧化氮合酶抑制剂L-NAME使主动脉cGMP含量进一步减少，主动脉对缩血管物质的收缩反应无进一步增强。各组大鼠的胸主动脉用L-NAME抑制一氧化氮生成后，对硝普钠的最大舒张反应无明显差别。 结论:2K1C肾性高血压大鼠主动脉收缩功能的改变可能与NO合成、释放减少和缩血管物质产生增多有关。     

NO在脂联素抑制高脂血症大鼠血小板聚集中的作用

目的: 探讨一氧化氮(NO)信号转导通路在脂联素抑制高脂血症血小板聚集机制中的作用。方法: 采用成年大鼠饲以高脂饲料14周,分离其血小板并以重组脂联素(rAPN)孵育。采用免疫荧光、Western blotting等方法观察检测血小板聚集、NO含量、超氧化物含量、内皮型一氧化氮合酶(eNOS)/诱导型一氧化氮合酶(iNOS)的表达和抗氧化物活性。结果: 采用rAPN处理能抑制高脂血症诱导的血小板聚集(P<0.05),并导致血小板NO的生成显著减少。同时,在高脂血症血小板中,采用rAPN处理还能显著减少超氧化物的生成(降低62%, P<0.05) 并增强其抗氧化能力(增加38%, P<0.05)。此外,高脂血症诱导的eNOS磷酸化的降低和iNOS表达的增加在rAPN处理后被显著逆转(P<0.05, P<0.01)。结论: 脂联素是一种抑制高脂血症血小板聚集的脂肪细胞因子,其机制与减少超氧化物水平、增加抗氧化物活性和阻断iNOS的表达有关。     

叶酸对去卵巢大鼠抗氧化酶、一氧化氮合酶和一氧化氮的影响

 目的: 观察叶酸对去卵巢大鼠抗氧化酶、一氧化氮合酶和一氧化氮的影响。方法: 40只3月龄健康雌性SD大鼠,随机分成5组:假手术组、去卵巢组、二乙基己烯雌酚(0.03 mg·kg^-1·d^-1)组、低剂量(5 mg·kg^-1·d^-1)叶酸组和高剂量(20 mg·kg^-1·d^-1)叶酸组。各组大鼠于术后1周开始灌胃给药,假手术组和去卵巢组给予蒸馏水,10周后,取L₅椎体和右股骨行骨密度(BMD)检测;测定血浆和骨匀浆总抗氧化能力(TAC)、谷胱甘肽过氧化物酶(GSH-Px)、丙二醛(MDA)、一氧化氮合酶(NOS)和一氧化氮(NO)水平。结果: 与假手术组比较,去卵巢组大鼠L₅椎体和股骨BMD显著降低(P < 0.01),血浆GSH-Px、NO和骨匀浆TAC、GSH-Px、NOS及NO水平明显降低(P < 0.01),MDA浓度升高显著(P < 0.01);与去卵巢组大鼠比较,高剂量叶酸组大鼠L₅椎体和股骨BMD增加(P < 0.01),骨匀浆TAC、GSH-Px、NOS和NO水平升高(P < 0.01),MDA浓度降低(P < 0.01),血浆GSH-Px和NO水平升高。结论: 去卵巢大鼠体内抗氧化酶、NOS和NO水平降低,氧化应激参与了去卵巢大鼠骨质疏松的发生;高剂量叶酸能提升去卵巢大鼠腰椎和股骨BMD,提高其体内抗氧化酶、NOS和NO水平,改善氧化应激,这可能是高剂量叶酸防治去卵巢大鼠骨质疏松的机制之一。     

一氧化氮及一氧化氮合酶抑制剂对髓核细胞线粒体功能的影响

BACKGROUND: Nitric oxide can interfere with the function of mitochondria, and accelerate the intervertebral disc damage and degeneration by interfering with the release of inflammatory cytokines. Nitric oxide is an important inflammatory cell medium leading to degeneration of intervertebral disc induced by pressure and other external factors. OBJECTIVE: To investigate the regulatory effect of nitric oxide and nitric oxide synthase inhibitor niacinamide on mitochondrial function and its association with biological behavior of rabbit nucleus pulposus. METHODS: Cultured nucleus pulposus cells of rabbit lumbar intervertebral disc were randomly divided into six groups: normal blank control group, 10 μmol/L sodium nitroprusside group, 100 μmol/L sodium nitroprusside group, 200 μmol/L sodium nitroprusside group, 0.05 g/L nicotinamide group (100 μmol/L sodium nitroprusside+0.05g/L nicotinamide), and 0.5 g/L nicotinamide group (100 μmol/L sodium nitroprusside and 0.5 g/L nicotinamide). Different doses of nitric oxide donor sodium nitroprusside and nicotinamide were added in the medium of each group. Three days after intervention, cell proliferation activity, intracellular ATP concentration, cell nitric oxide synthase activity, cellular reactive oxygen species level, and mitochondrial membrane potential were detected respectively. RESULTS AND CONCLUSION: (1) After 3 days of rabbit nucleus pulposus cells intervened by different concentrations of sodium nitroprusside, intracellular nitric oxide synthase content increased with sodium nitroprusside volume increase, and ATP concentration decreased along with sodium nitroprusside volume increase; there were significantly differences between the normal control group and sodium nitroprusside groups (P < 0.01). (2) Reactive oxygen species could be increased in the sodium nitroprusside group. Niacinamide groups indicated a dose-dependent manner to improve the increase of cellular reactive oxygen species levels with sodium nitroprusside intervention (P < 0.01). (3) In the sodium nitroprusside groups, nucleus pulposus cell membrane potential decreased. In the niacinamide groups, sodium nitroprusside- induced decline in mitochondrial membrane potential was reduced (P < 0.01). (4) Niacinamide groups also indicated a dose-dependent manner to improve the proliferative activity of nucleus pulposus cells as compared with sodium nitroprusside groups (P < 0.01). Significant differences were determined between the two groups (P < 0.01). (5) Results suggest that the excess nitric oxide can damage mitochondrial metabolic function of rabbit nucleus pulposus cells and cause cell energy metabolism. Niacinamide can reverse these damages by inhibiting nitric oxide synthesis, thereby contributing to the prevention against intervertebral disc degeneration. 中国组织工程研究杂志出版内容重点：组织构建;骨细胞;软骨细胞;细胞培养;成纤维细胞;血管内皮细胞;骨质疏松;组织工程