Changes in L-arginine/nitric oxide pathway of the aorta in septic shock rats

AIM:To observe the change of nitric oxide (NO) generation system in the vascular adventitia, media and intima in septic shock rats.METHODS:The septic shock model was made in rats by caecal ligation and puncture. The intima, media and adventitia of the rat aorta were separated. NO production (NO₂^-), nitric oxide synthase(NOS) activity and L-arginine (L-Arg) transport were measured, separately. Inducible NOS (iNOS) distribution was detected by immunohistochemistry.RESULTS:Both in early and late stage of septic shock, NO₂^- from the intima was decreased by 66.1% and 78.9%(P<0.01), while NO₂^- from the media was increased by 1.1 and 2.2 folds(P＜0.01), and the adventitia 9.6 and 18.6-fold (P＜0.01), as compared with the sham group, respectively. The changes of NOS activity and the L-arginine transport in the intima, the media layer and the adventitia of the aorta in the septic shock rat paralleled with that of NO₂^- in these tissues. The results of iNOS immunohistochemistry showed that there were obviously positive staining in the media layer and adventitia, especially the adventitia of the rat aortas in septic shock, as compared with that in the sham control.CONCLUSIONS:During septic shock, NO production in the aortic intima was progressively suppressed. However, it was progressively increased in the aortic medial layer and adventitia, especially the adventitia with shock processes. These changes result from different changes of L-arginine transport, NOS activity and its expression in three layers of the aorta from the septic shock rat.     

Changes of L-arginine,NOS/NO pathway in adventitia of rats with sepsis

AIM: In this study, we aimed to explore the alteration and pathophysiological significance of the L-arginine (L-Arg)/NOS/NO pathway in the adventitia of rats with sepsis. METHODS: Sepsis was induced by cecal ligation and puncture (CLP). Rat cardiac function was determined. NO generation, NOS activity and L-Arg transport were measured. The iNOS mRNA levels was determined by using RT-PCR. RESULTS: Cecal ligation and puncture induced severe sepsis with severe low glucose, high lacticemia and cardiac function inhibition. The iNOS activity was increased by 2.8-fold compared with controls (P<0.01) and the iNOS mRNA level was elevated-6-fold (P<0.01). The NO level in plasma and incubation media (incubation for 40 min) in the sepsis group was increased by 144% and 273% (both P<0.01), respectively. CONCLUSION: The results demonstrated that the L-Arg,NOS/NO pathway was activated in vascular adventitia of rats with sepsis shock. The aortic adventitia L-Arg/NOS/NO pathway might play an important role in the pathogenesis of sepsis and septic shock.     

Effects of taurine on the change of apoptosis induced by IL-1β, TNF-α and IFN-γ in rat pancreatic islet cells

AIM: To investigate the changes of apoptosis in isolated pancreatic islet cells, insulin secretion, expression of Bcl-xL and Bax induced by combination of IL-1β, TNF-α and IFN-γ, and effects of taurine on them.METHODS: Isolated pancreatic islet cells from Wistar rat were incubated in monolayer in vitro. NO^-₂/ NO^-₃ production, NOS activity, insulin secretion, the protein expression of Bcl-xL and Bax, percentage of islet cell apoptosis and DNA fragmentation in pancreatic islet cells incubated with combination of IL-1β, TNF-α and IFN-γ were measured, and the effects of taurine on the changes of them were further investigated. RESULTS: Combination of IL-1β, TNF-α and IFN-γ induced a significant increase in percentage of pancreatic islet cell apoptosis, NO^-₂/ NO^-₃ production and NOS activity, DNA ladder appearance, a decrease in insulin content, up-regulation in the protein expression of Bax and down-regulation in the protein expression of Bcl-xL (P<0.01), which were blocked by addition of taurine (P<0.01). These effects occurred in a dose dependent manner.CONCLUSION: Taurine attenuates β cell apoptosis induced by IL-1β, TNF-α and IFN-γ. The mechanism of which may be the inhibition of NOS activity and the decrease of NO production as well as the downregulation of Bax/Bcl-xL proportion.     

Effect of gingko biloba extract on liver from experimental type 2 diabetic rats

AIM:To study the protective effect of the ginkgo biloba (EGB) extract on liver from experimental type 2 diabetic rats and to explore its possible mechanism. METHODS:Thirty-nine male Sprague-Dawley rats were divided randomly into four groups: normal control group, high-fat group, diabetic group and EGB-treated group. After fed with high-fat diet for 4 weeks, the later two groups were injected with streptozotocin intraperitoneally to induce type 2 diabetes mellitus. EGB-treated group was injected intraperitoneally with EGB at a dose of 8 mg·kg^-1·d^-1, and the other three groups were treated with normal saline of the same volume. After 8 weeks, the morphologic change of hepatic tissue was observed under transmission electron microscope (TEM) and light microscope (LM), respectively. In addition, the activity of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-PX), total nitric oxide synthase (TNOS), inducable nitric oxide synthase (iNOS) and the content of malondialdehyde (MDA), nitric oxide (NO) in liver homogenate were detected biochemically. RESULTS:Obvious liver fatty degeneration, apparent decrease of glycogen granules in cytoplasm of hepatocytes under light microscope and hepatocytes pyknosis, lots of lipid deposits in cytoplasm of hepatocytes, proliferation of hepatic stellate cells and collagen under TEM were observed in diabetic group. The activity of SOD, CAT, GSH-PX decreased but the activity of tNOS, iNOS and the content of MDA, NO^-₂/NO^-₃ increased in diabetic group compared with normal control group. The pathological change was relieved in EGB-treated group. The activity of SOD, CAT, GSH-PX increased, the activity of tNOS, iNOS and the content of MDA, NO^-₂/NO^-₃ decreased in the liver of rats in EGB-treated group compared with diabetic group. CONCLUSION:EGB exerts a beneficial effect on liver in experimental type 2 diabetic rats. Anti-lipid peroxidation and suppression of NO production may be involved in this process.     

Effects of celecoxib on cardiac myocyte apoptosis after myocardial infarction

AIM: To investigate the effects of celecoxib, a selective cyclooxygenase-2 inhibitor, on antioxidative capability and apoptosis of cardiac myocytes after myocardial infarction. METHODS: 24 New Zealand rabbits were divided into three groups randomly (8 in each group): sham-operated group (sham group), myocardial infarction group (MI group), celecoxib group (Cele group, 10 mg kg^-1·d^-1, qd, with the drugs gastric gavage for six weeks). The NO concentration, total antioxidative capability (T-AOC), the activity of constitutive nitric oxide synthase (cNOS) and inducible NOS (iNOS) in cardiac tissue homogenate, adjacent to the infracted area, were detected. The pathological changes were observed by light microscope and electron microscopy. The expressions of Bcl-2 and Bax protein in myocytes were observed using immunohistochemistry, and the degree of apoptosis were examined by TUNEL. RESULTS: Cardiac tissue in MI group presented interstitial edema, fibroplastic proliferation, inflammatory cellular infiltration, and vacuolar degeneration in cardiac myocytes. The results of electron microscopy showed that myocytes presented more changes caused by ischemic injury: widened interspace of myofibril, disordered myofibrillae, focal lysis of myofilament, ectasia of sarcoplasmic reticulum. In Cele group, the pathological changes were light, the NO^-₂/ NO^-₃ concentration, the activity of iNOS were lower (P<0.05), while the activity of cNOS and T-AOC were higher (P<0.05) than those in MI group. The expression rate of Bcl-2 protein in Cele group was higher than that in MI group, while the Bax was lower (P<0.01). The number of apoptotic myocytes was lower than that in MI group (P<0.01).CONCLUSION: Celecoxib decreases the number of apoptotic cardiomyocytes and increases the antioxidative capability after myocardial infarction.     

Effect of taurine on L-arginine/NO pathway in erythrocytes of rats of hypertension with insulin resistance induced by fructose

AIM and METHODS:The present study observed the change of L-arginine(L-Arg)/Nitric oxide(NO)pathway in ergthrocytes in hypertension with insulin resistance rat induced by fructose and the effect of taurine on L-Arg/NO pathway.RESULTS:Drinking 4%fructose, while inducing blood pressure, glucose and plasma insulin contents increase, obviously decreased the maximal velocity of L-Arg transport about 31%and 37%(P<0.01), more than that of control group in total and Y⁺ carrier, the NO synthase(NOS)activity, nitrite(NO₂^-)content and cyclic guanylate monophosphate(cGMP)level more than that of control group, but obviously enhanced Michaelis Constant(Km)about 35%and 30%(P<0.01)more than that of control group in total and Y⁺ carrier transport.The taurine treatment significantly counteracted the above changes.CONCLUSION:There exists a functional disturbance in L-Arg/NO system in the erythrocyte of hypertension rats with insulin resistance, but taurine can obviously enhanced the maximal velocity of L-Arg transport and NOS activity.Thus, it appears that taurinemay have vital value in the treatment of hypertension with insulin resistance.     

The renal L-arginine/nitric oxide pathway and erythrocyte L-arginine transport in spontaneously hypertensive rats

AIM: To investigate the changes of the renal L-arginine /nitric oxide pathway and the relationship of L-arginine transport between kidney and erythrocytes in spontaneously hypertensive rat (SHR). METHODS: Sixteen week old SHR, 16 week old SHR with captopril (CAP) treated for four weeks and 16 week old WKY rats were used in the experiment. L-arginine transport, NO synthase(NOS) activity, nitrite and cyclic GMP (cGMP) content were measured in renal tissue or erythrocytes. RESULTS: In the renal tissue, compared with that of WKY group, the Vmax of high-or low-affinity L-arginine transporter, NOS activity, NO₂^- and cGMP content of SHR group were significantly decreased (P＜0.01 or P＜0.05). The Vmax of high-affinity L-arginine transporter and NOS activity of CAP group were significantly enhanced as compared with SHR group (+90%, P＜0.01; +58.6%, P＜0.05). The NOS activity had significant positive correlation with the Vmax of high-affinity L-arginine transporter (r=0.585, P＜0.05). The changes of erythrocyte L-arginine transport were the same as that of kidney. The Vmax of SHR group was lower than that of WKY group (-30%, P＜0.01), and the Vmax of CAP group was higher than that of SHR group (+26.5%, P＜0.01). Km was not significantly changed. There is a positive correlation between the Vmax of L-arginine transport in erythrocyte and the Vmax of high- or low-affinity L-arginine transporter in renal tissue, (r=0.8434, P＜0.01, high-affinity; r=0.5255, P＜0.05, low-affinity). CONCLUSION: There existed a functional inhibition in L-arginine/nitric oxide pathway in the kidney of SHR. It can be recovered obviously by captopril treatment. The changes of L-arginine transport in kidney coincide with that in erythrocyte.     

Changes in L-arginine/NO pathway of erythrocytes in patients with essential hypertension

AIM:To investigate the changes of L-arginine/nitric oxide(L-Arg/NO) pathway and the characteristics of L-Arg transport in erythrocytes (RBC) in patients with essential hypertension(EH). METHODS: 12 EH patients were studied with 10 normotensive people as control. The nitric oxide (NO) production was assayed by measuring the nitrite in medium using Greiss reaction. NO synthase activity was measured according to the method described by Ghigo. In order to achieve zero-trans condition, erythrocytes were incubated at 37℃ for 3 h and then L- Arg transport of RBC were determined by measuring the influx of radiolabelled L-arginine by Deliconstantins described method. RESULTS: In EH patients, NO production was lower than that in control (P＜0.01) and the cGMP quantity was only 72.8% of control (P＜0.01). NOS activity of EH patients decreased to 47.8% of control. Saturable influx of L-Arg was mediated by the classical cationic amino acid transport system Y^＋ and Y^＋L system with high affinity. Under zero-trans condition, the ability of L-Arg transport by RBC in EH patient was lower than control. The V_max for total L-Arg transport and via system Y^＋ respectively decreased 36.8% and 42.5% compared with control. But V_max or L-Arg transport via system Y^＋L was not affected by EH. In EH patients K_m value for total, system Y^＋and system Y^＋L had no difference with control. CONCLUSION: The present study suggested that there is disturbance of L-Arg/NO pathway in human erythrocytes from patient with EH.     

Role of nitric oxide in the inhibition of lipopolysaccharide-induced thoracic aortic hyporeactivity by cholecystokinin in vitro

AIM:To investigate the effect of cholecystokinin octapeptide(CCK-8) on the L-arginine-nitric oxide(NO) pathway in rabbit thoracic aortae treated with lipopolysaccharide(LPS).METHODS:The isolated thoracic aortic rings(TARs) from rabbits were incubated with LPS, LPS+CCK or vehicle for 14 h. Then the contractility to phenylephrine(PE) by TARs and the response to L-arginine(L-Arg) by pre-contractile TARs were measured. In addition, we added NO synthase(NOS) inhibitors aminoguanidine(AG)and N^ω-nitro-L-arginine(L-NNA) into organ baths to observe the changes of vascular contractility to PE. NOS activity in isolated TARs were also detected. RESULTS:Incubation of TARs with LPS for 14 h resulted in an increase of NOS activity and a reduction of contractility to PE. Treatment with CCK-8 significantly inhibited the increased NOS activity in thoracic aortae and improved the hypocontractility of TARs to the same degree as AG.CONCLUSION:CCK-8 may improve the hypocontractility of TARs induced by LPS by inhibiting the activity of NOS.     

Effect of nitric oxide on adiponectin-induced inhibition of platelet aggregation in hyperlipidemia rats

AIM: To investigate the mechanism that adiponectin inhibits platelet aggregation via nitric oxide (NO) signaling pathway. METHODS: Adult rats were fed with normal or high-fat diet for 14 weeks. Their platelets were immediately isolated and treated with or without recombinant full-length adiponectin (rAPN). The platelet aggregation, NO and superoxide production, endothelial nitric oxide synthase (eNOS)/inducible NOS (iNOS) expression, and antioxidant capacity were determined. RESULTS: Treatment with rAPN inhibited platelet aggregation induced by hyperlipidemia (P<0.05). Interestingly, total NO, a crucial molecule depressing platelet aggregate and thrombus formation, was significantly reduced, rather than increased in rAPN-treated platelets. Treatment with rAPN significantly decreased superoxide production by 62% (P<0.05) and increased antioxidant capacity by 38% (P<0.05) in hyperlipidemic platelets. Importantly, hyperlipidemia-induced reduction of eNOS phosphorylation and increase in iNOS expression were markedly reversed by rAPN treatment (P<0.05 and P<0.01, respectively). CONCLUSION: Adiponectin is an adipokine that inhibits platelet aggregation by enhancing eNOS activation and attenuating oxidative/nitrative stress including blockage of iNOS expression and superoxide production.     

Increase in proliferation of adventitial fibroblasts at early stage of atherosclerosis in apoE(-/-) mice

AIM: To study the relationship between the proliferation of adventitial fibroblasts and the early formation of atherosclerotic lesion. METHODS: ApoE(-/-) mice and wild-type C57BL/6 black mice (6-week old) were used in this experiment. 5-Bromo-2-deoxyuridine (BrdU) was administered 24 h before the animals were sacrificed at time points of 0, 2, 4 or 10 weeks after hyperlipidic diet, respectively. The ascending aorta was removed for serial sectioning. The morphological changes of the aortic tissues were observed under microscope with HE staining. Some sections of the aorta were used to observe the BrdU labeling in the adventitia and intima at different time points by the method of immunohistochemistry. In addition the arterial adventitial fibroblasts derived from apoE(-/-) mice and C57BL/6 mice after hyperlipidic diet for 2 weeks were cultured. The proliferation of the cells was examined by BrdU incorporation. The cell cycle was examined by flow cytometry. RESULTS: In vivo the BrdU-labeled cells were first found in the adventitia of apoE(-/-) mice after feeding with hyperlipidic diet for 2 weeks, the time point that no visible intimal lesion formation was found, and then subsequently emerged in the intimal lesion. No BrdU labeling was observed in C57BL/6 mice at any time point. The number of BrdU labeled cells in the adventitial fibroblasts of apoE(-/-) mice was significantly higher than that in C57BL/6 mice in vitro (P<0.01). The adventitial fibroblasts of apoE(-/-) mice exhibited higher percentages of S and G₂/M phases than those in C57BL/6 mice (P<0.05). CONCLUSION: The proliferation of arterial adventitial fibroblasts might participate in the early formation of atherosclerotic lesions.     

Vasodilatatory effect and mechanism of CH2Cl2 extract of flos magnoliae on isolated rat thoracic aorta

AIM: To characterize the vasodilatatory effect of CH₂Cl₂ extract of flos magnoliae (CEF) on isolated rat thoracic aorta and to elucidate its possible mechanism. METHODS: The thoracic aorta was isolated from male Sprague-Dawley (SD) rats and the isometric tension of aortic rings with or without endothelium was measured. RESULTS: CEF (0.1-1 000 mg/L) produced concentration-dependent, endothelium-independent relaxations in phenylephrine (PE)-contracted aortic rings. The maximum relaxation induced by CEF was 78.68%±6.03% in endothelium intact rings and 64.98%±13.90% in endothelium removed rings while the forskolin (1 μmol/L)-induced vasodilation was obtained as 100%. The vasodilatatory effect of CEF was not statistically inhibited by 10 μmol/L glibenclamide (Glib), 3 mmol/L tetraethylammonium (TEA), 100 μmol/L BaCl₂ and 10 μmol/L 1H- -oxadiazole- -quinoxalin-1-one (ODQ) in the preparations without endothelium. The CEF pre-treatment significantly inhibited vasoconstrictions to angiotensin Ⅱ (AngⅡ), prostaglandin F_2α, (PGF_2α), dopamine (Dopa), vasopressin (Vaso), 5-hydroxytryptamine (5-HT) and PE by 91.31%, 82.11%, 95.32%, 90.53%, 72.22% and 83.63%, respectively (P<0.01). In Ca²⁺-free medium treated endothelium removed aortic ring, incubation with CEF at concentration of 82 mg/L significantly attenuated intracellular Ca²⁺ release by PE. In Ca²⁺-free + high potassium medium incubated aortic rings without endothelium, CEF (82 mg/L) markedly inhibited potassium-stimulated Ca²⁺-dependent contraction which was mainly due to Ca²⁺ influx (P<0.01).CONCLUSION: CEF induced vasorelaxation is mainly related to interfering intracellular calcium homeostasis by blocking Ca²⁺ influx and intracellular Ca²⁺ release.     

Relationship between the tissue neutral endopeptidase and the adrenomedullin in blood and tissues of rats with septic shock

AIM: The activity and expression of neutral endopeptidase (NEP) and the adrenomedullin (ADM) contents in various tissues were observed in septic shock and control rats to study the possible role of NEP in the change of ADM contents in tissues during septic shock. METHODS: The septic shock model of rats were established by cecal ligation and puncture (CLP). ADM contents, NEP activities, level of NEP mRNA and NEP protein were measured. RESULTS: (1) In early septic shock (ES), the ADM contents were generally higher in detected tissues, the NEP activity in left ventricle and small intestine were lower and was higher in blood than those in controls, and in lung, kidney and aorta were similar with the controls. NEP immunoreactive staining were less in lung, left ventricle, endothelium and media of aorta, but more in adventitia of aorta and kidney than those of the controls; (2) In late septic shock (LS), the ADM contents in small intestine was less but in plasma and other tissues were higher, and the NEP activity were less in plasma and other tissues than those in ES. The NEP immunoreactive staining were less in heart, endothelium and media of aorta, lung and kidney than those in ES, and was no significant change in adventitia of aorta compared with those of ES. RT-PCR found that NEP gene expression were significantly less in left ventricle, aortas, lung and small intestine than those in the controls. CONCLUSIONS: In septic shock rats, the NEP activity changes heterogeneously but the ADM contents elevate in most tissues. These results indicate that during the septic shock, the local concentrations and actions of ADM in various tissues may be regulated differently by the NEP.     

In vitro anti-platelet aggregative effect of procyanidins isolated from grape seeds

AIM: To study the possible anti-platelet aggregative mechanisms of procyanidins (PC) isolated from grape seeds in vitro. METHODS: Platelet-rich plasma (PRP) and platelet-poor plasma (PPP) were prepared from the blood of healthy volunteers. PC,diphenylene iodonium(DPI,a nonspecific NADPH oxidase inhibitor) and apocynin (a specific NADPH oxidase inhibitor) were used to observe the effects on collagen-induced platelet maximum aggregation rate using platelet aggregometer. The influences of PC on platelet NADPH oxidase activity, NO content and superoxide anion (O₂^-·) level were evaluated by chemiluminescence spectrometer. The role of PC in the expression of activated platelet markers (PAC-1 and CD62P) was observed by flow cytometry. RESULTS: PC (100 μmol/L), apocynin (10 μmol/L) and DPI (100 μmol/L) significantly inhibited collagen-induced maximum platelet aggregation rate (P<0.01). In collagen-activated platelets, NO content reduced and O₂^-· level increased,both of which were recovered by PC at concentration of 100 μmol/L (P<0.05). PC also obviously inhibited NADPH oxidase activity (P<0.01), and significantly down-regulated PAC-1 and CD62P expression (P< 0.05) in platelets. CONCLUSION: Procyanidins isolated from grape seeds have the anti-platelet aggregation function through inhibiting NADPH oxidase activity, further influencing platelet NO and O₂^-· levels.     

Role of polyamines in L-arginine inhibiting isoproterenol induced cardiac hypertrophy rat

AIM: To explore the role and possible mechanism of polyamine in L-arginine inhibiting cardiac hypertrophy induced by isoproterenol (ISO). METHODS: Hypertrophic model of rats was established using ISO. Pretreated with L-arginine, hypertrophy status of rats was determined by hypertrophy coefficient, collagen content and the expression of ANP mRNA. High performance liquid chromatography (HPLC) was used to measure the concentrations of polyamines. Western blotting was performed to detect the expressions of ornithine decarboxylase (ODC) and spermidine/spermine N1-acetyltransferase (SSAT). The activity and levels of NOS and NO in serum were also observed. RESULTS: Hypertrophy coefficient and expression of ANP mRNA increased significantly after injection of ISO for 7 d. Moreover, cardiac muscle fibres became thick and disorganized. Pretreated with L-arginine, the above index decreased. Meanwhile, the concentration of polyamine was decreased and plasma NO content and NOS activity were increased, the expression of ODC was downregulated and the expression of SSAT was upregulated. CONCLUSION: Exogenous L-arginine inhibits cardiac hypertrophy through downregulating L-arginine/polyamine pathway and upregulating L-arginine/NO pathway.     

Effect of inhaled nitric oxide on aquaporin expression in newborn rat lung in acute hyperoxic lung injury

AIM:To investigate the effect of inhaled nitric oxide on aquaporin expression and alveolar epithelial fluid transport in newborn rats with acute hyperoxic lung injury. METHODS:32 newborn SD rats were randomized to breathe for 48 h room air (C), >95%O₂ (O), >95%O₂+10^-5 NO (NO only in the first 24 h, ONO), room air + NO (CN). Then, the rats were killed, the lung wet-to-dry weight ratio (Q_W/Q_D), the histology, and AQP1, AQP5, α₁-NKA, α-ENaC mRNA expressions in the lungs were measured. RESULTS:Compared with C group, the Q_W/Q_D in O group significantly increased (P<0.01), and AQP1 mRNA expression decreased significantly (P<0.01). Compared with O group, ONO group had a lower level of Q_W/Q_D (P<0.05), and AQP1 mRNA expression increased (P<0.05). AQP5 mRNA expression in all groups remained unchanged. CONCLUSION:In newborn rats with acute hyperoxic lung injury, inhaled 10-5 nitric oxide for 24 h may attenuate lung edema and increase AQP1 mRNA expression, suggesting that inhaled 10^-5 nitric oxide for 24 h may promote the AQP1 expression in lung in this model of acute lung injury.     

Effects of luteolin on endothelial cell injury induced by H2O2

AIM: To study the effect of luteolin on endothelial cell injuries induced by H₂O₂. METHODS: Endothelial cells were cultured in vitro and divided into seven groups: control; solvent; H₂O₂; quercetin+H₂O₂; luteolin-L+H₂O₂; luteolin-M+H₂O₂; luteolin-H+H₂O₂ group, respectively. Endothelial cells were incubated with 750 μmol/L H₂O₂ for 18 h or 14 h in the absence or presence of various concentrations of luteolin and quercetin. The expression of caspase-3, the pro-apoptotic factors, was detected by immunohistochemical technique, and the apoptotic index was detected by flow cytometry. Meanwhile, the amount of malondialdehyde (MDA), nitric oxide (NO), lacate dehydrogenase (LDH) in serum, and cell viability were measured. RESULTS: Incubation of endothelial cells with H₂O₂ for 18 h elicited the increase in the extent of immunostaining for caspase-3, the rate of apoptosis, the release of LDH, and the number of dead cells accompanied by the decrease in the content of NO in the medium, which were inhibited by pretreatment of luteolin at concentrations of 0.5-50 μmol/L in a concentration-dependent manner (P<0.01). CONCLUSION: Luteolin possesses a protective effect against endothelial cell injuries induced by H₂O₂, which may be related with anti-oxidation, increasing the concentration of NO and inhibiting the activation of caspase-3.     

Effects of hemorrhagic shock on BKCa channel tyrosine phosphorylation level in mesenteric artery in rats

AIM: To study the effects of hemorrhagic shock on BK_Ca channel tyrosine phosphorylation in rat superior mesenteric artery and the role of nitric oxide (NO) in BK_Ca channel tyrosine phosphorylation. METHODS: The hemorrhagic shock model [(35±5)mmHg] was established in rats and the whole lysate of superior mesenteric artery were extracted and analyzed by immune precipition (IP) and immunoblotting. The tyrosine phosphorylation levels of BK_Ca channel alpha-subunit in mesenteric artery in hemorrhagic shock rats were investigated, and the modulation of BK_Ca channel alpha-subunit tyrosine phosphorylation by NO and its dose-and time-dependended relationships were observed. RESULTS: The tyrosine phosphorylation level of BK_Ca channel alpha-subunit in mesenteric artery in rats increased significantly after hemorrhagic shock 2 h and 4 h (P<0.01 ), and L-arginine (5×10^-5-5×10^-4 mol/L) up-regulated BK_Ca channel alpha-subunit tyrosine phosphorylation in primary cultured VSMC in a 30 min incubation and without significant decrease after 2 h; L-arginine induced BK_Ca channel alpha-subunit tyrosine phosphorylation in a dose-dependent manner. CONCLUSION: Hemorrhagic shock enhances BK_Ca channel tyrosine phosphorylation in resistant artery in rats, and NO is involved in this process.     

一氧化氮参与乙烯诱导黄瓜不定根的形成

以黄瓜(Cucumis sativus L.)切去初生根的幼苗外植体为试材,研究了乙烯和一氧化氮(NO)对其不定根形成的影响及其相互关系。结果表明,外源乙烯供体乙烯利(Ethrel)可显著促进黄瓜外植体不定根的形成,呈现明显的剂量效应,最适浓度为0.5μmol·L~(-1)。Ethrel和NO共同处理的外植体不定根的数量和根长显著高于Ethrel和NO单独处理,但Ethrel的促进作用可被NO的清除剂c-PTIO、一氧化氮合酶(NOS)抑制剂L-NAME和硝酸还原酶(NR)抑制剂NaN_3所逆转,说明乙烯和NO在黄瓜外植体不定根形成过程中具有协同诱导作用。外源乙烯引起黄瓜外植体内源NO含量的增加,亦提高了植株体内合成NO的NOS和NR酶的活性以及NOS和NR基因的相对表达量。可见,NO在乙烯诱导黄瓜不定根形成的信号途径中起重要作用。