Role of myosin-light-chain kinase in biphasic contractile activity of lymphatics isolated from hemorrhagic shock rats

AIM: To elucidate the mechanism by which myosin-light-chain kinase (MLCK) modulates the biphasic contractile activity of lymphatics isolated from the rats subject to hemorrhagic shock (HS). METHODS: Male Wistar rats were randomiz to control group and HS group. In HS group, the rats were subject to HS and then further divided into HS 0 h, 0.5 h, 1 h, 2 h and 3 h subgroups. Thoracic ducts of control and shock rats were isolated and used to determine the protein levels of phosphorylated MLCK (p-MLCK). In addition, thoracic ducts obtained from control, 0.5 h- and 2 h-shocked rats were used to observe the contractile properties of lymphatics by a pressure myograph in vitro . Lymphatic rings were prepared and incubated with ML-7 (a specific inhibitor of MLCK) or substance P (SP, an agonist of MLCK). During the experiment, the contractile frequency (CF), end-diastolic diameter, end-systolic diameter and passive diameter in Ca²⁺-free PSS buffer were measured and used to calculate the lymphatic tonic index (TI), contractile amplitude (CA) and fractional pump flow (FPF) as the indexes of lymphatic contraction activity. RESULTS: The levels of p-MLCK in lymphatics in 0 h- and 0.5 h-shocked rats were significantly increased compared with the control rats, and it was gradually decreased with the development of shock. The values of CF, TI and FPF in 0.5 h-shocked lymphatics were significantly increased at transmural pressure of 1, 3 and 5 cmH₂O compared with those in control group, and significantly blunted by ML-7. SP obviously increased the suppressive effects induced by ML-7 and restored the values of CF, TI and FPF to the levels of HS 0.5 h group. CF, TI and FPF in 2 h-shocked lymphatics significantly declined under different transmural pressure as compared with those in control group, and significantly elevated by SP. Similarly, ML-7 depressed the effects of SP. No significant difference was found in CA between 0.5 h- and 2 h-shocked lymphatics. SP decreased the CA of lymphatics obtained from 2 h-shocked rats and this effect was suppressed by ML-7. However, both agents had no effects on CA of 0.5 h-shocked lymphatics. CONCLUSION: MLCK, as an essential enzyme that influences the contraction of lymphatic smooth muscle cells, involves in the modulation of biphasic changes of lymphatic contractile activity during the process of HS.     

Substance P enhances pump function of isolated lymphatics from hemorrhagic shock rats

AIM: To establish a technique of lymphatic perfusion in vitro and to determine the effect of substance P (SP) on lymphatic contractility during the process of hemorrhagic shock (HS). METHODS: Male Wistar rats were randomly divided into control group (surgical procedure only) and HS group . Thoracic ducts were isolated from HS rats at the corresponding time points. The segment of thoracic duct was prepared, perfused in vitro at the transmural pressure of 3 cmH₂O and stimulated with gradient concentrations of SP to measure the lymphatic contractile activity. The end-systolic diameter, end-diastolic diameter, contraction frequency (CF) and passive diameter of isolated lymphatics were measured. The contraction amplitude (CA), tonic index (TI) and fractional pump flow (FPF) were also calculated.RESULTS: SP increased lymphatic CF, TI and FPF, and the effects were enhanced with the increase in the concentration of SP. The CF, TI and FPF of 2 h- and 3 h- shocked lymphatics were elevated to/over the value of baseline levels before the experiment by SP at the concentration starting from 3×10^-8 mol/L. At the same concentration of SP, the CA of lymphatics showed no significant statistical difference among the groups. However, with the increase in SP concentration, the lymphatic CA had a downward trend in all groups.CONCLUSION: SP enhances the pump function of lymphatics not only under physiological condition, but also in shock during different stages.     

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.     

Estrogen treatment enhances mesenteric lymphatic contractility in rats after hemorrhagic shock

AIM To investigate the effects of 17β-estradiol （E2） treatment on the mesenteric lymphatic microcirculation and isolated lymphatic contractility in rats after hemorrhagic shock, and to explore the relationship between contractility and the difference between intra- and extracellular calcium ion concentrations （［Ca²⁺］） of lymphatic smooth muscle cells （LSMCs）. METHODS Male Wistar rats were divided into sham group, shock group and shock+E2 group. The rats were subjected to hemorrhage ［（40±2） mmHg for 90 min］ and resuscitation with or without subcutaneous injection of E2 （2 mg/kg）. After resuscitation for 3 h, the mesenteric lymphatic microcirculation in vivo was observed. Moreover, the isolated mesenteric microlymphatic rings were prepared for the observations of lymphatic contractility evaluated by the indexes including end-systolic diameter, end-diastolic diameter, contraction frequency （CF） and passive diameter. Meanwhile, the difference between intra- and extracellular ［Ca²⁺］ of LSMCs was recorded during lymphatic contraction. RESULTS Treatment with E2 significantly enhanced the CF, total contractile fraction and lymphatic dynamics index in vivo in the rats after hemorrhagic shock, and increased the CF, the fractional pump flow and the difference between intra- and extracellular ［Ca²⁺］ of LSMCs in isolated lymphatics from the shocked rats （P<0.05）. CONCLUSION Estrogen treatment enhances lymphatic contractility in rats after hemorrhagic shock, which is related to enhancement of difference between intra- and extracellular ［Ca²⁺］ of LSMCs.     

Mechanism of mesenteric lymph reperfusion aggravates multiple organ injury in superior mesenteric artery occlusion shock rats

AIM: To explore the mechanism of mesenteric lymph reperfusion (MLR) aggravates multiple organ injury in superior mesenteric artery occlusion (SMAO) shock rats. METHODS: Male Wistar rats were randomly divided into 4 groups: in sham group, only anesthetization and operation were performed; in MLR group, occlusion of mesenteric lymphatics (ML) for 1 h followed by 2 h of reperfusion; in SMAO group, occlusion of superior mesenteric artery (SMA) for 1 h followed by 2 h reperfusion; in MLR+SMAO group, occlusion of SMA and ML for 1 h followed by 2 h of reperfusion. The homogenates of liver, kidney, myocardium and lung were prepared for determining the activities of free radical, nitric oxide, myeloperoxidase (MPO) and cell membrane ATPase. RESULTS: The MDA, NO contents and NOS, MPO activities of multiple organic homogenate in SMAO and MLR+SMAO group were higher than those in sham and MLR group, and these indexes in MLR+SMAO were increased significantly than those in SMAO group. The SOD and ATPase activities of muliple organic homogenate in SMAO and MLR+SMAO group were lower than those in sham and MLR group, and those in MLR+SMAO group was decreased obviously than those in SMAO group. CONCLUSION: The MLR enhances the multiple organ free radical injury, NO synthesis and release, PMN detention and decreases the activity of cell membrane ATPase, aggravating the major organs injury in SMAO shock rats. Intestinal lymphatic pathway plays an important role in the pathogenesis of SMAO shock.     

Effect of nitric oxide on apoptosis in lung injury following ischemia-reperfusion of hind limbs

AIM: To investigate the injury of lung and the role of cell apoptosis in the pathogenesis of acute lung injury following ischemia-reperfusion of hind limbs and the influence of nitric oxide (NO) to apoptosis.METHODS: Referring to our laboratory normal method,the model rats,which underwent 4 hours ischemia and 4 hours reperfusion of hind limbs were made.L-arginine (L-Arg) and N-nitro-L-arginine methyl ester (L-NAME) was administrated respectively to these rats before the experiment.Apoptosis was detected by TdT-mediated dUTP nick end labeling (TUNEL),respectively.The radioimmunoassay (RIA) was used to detect level in the expression of TNF-α.The immunohistochemistry (IHC) method was used to detect the level in the expression of Bcl-2,Bax,caspase-3 and TNF-α.The morphologic changes were observed under microscope,respectively.The results of the RIA and the IHC were analyzed quantitatively by relative computer analytical system.RESULTS: After rats’s hind limbs suffered from ischemia-reperfusion,the apoptosis in alveolar epithelial cells and pulmonary vascular endothelial cells was found.The expression of TNF-α,caspase-3 and Bax increased.Compared with IR rats,the expressions of TNF-α,caspase-3 and Bax were not obvious in the L-Arg administrated group,but the expression of Bcl-2 was obvious in that group.Compared with IR rats,the expressions of TNF-α,caspase-3 and Bax were obvious in the L-NAME administrated group,but the expression of Bcl-2 was not obvious in that group even weaker than normal ones.CONCLUSION: Apoptosis participated in acute lung injury following ischemia-reperfusion of hind limbs.The excess expression of TNF-α related with apoptosis of alveolar epithelial cells and pulmonary vascular endothelial cells.NO may reduce the occurrence of apoptosis and other lung injury through down-regulating the level in the expression of TNF-α.     

Effect of L-arginine on intimal proliferation and expression of related cell cycle regulatory factors after vascular injury in rats

AIM:To investigate the effect of L-arginine (L-Arg) on intimal proliferation and expression of related cell cycle regulatory factors after vascular injury in rats. METHODS:Rats were divided into three groups :sham operation group, balloon injury group(this group included balloon 48 h,7 d and 14 d subgroup) and balloon+L-Arg group. Neointima area were calculated morphologiocally. The expression of cyclin dependent kinase-2(CDK2),cyclin E and proliferation cell nuclear antigen (PCNA) were measured by means of immunohistochemical technique and computer image analyzer. RESULTS:After vascular balloon injury, the level of plasma NO decreased, CDK2、cyclin E and PCNA expressed in the media at 48 h and in the neointima at 7 d and 14 d but with low and undetected expression in the media, the expression of CDK2, cyclin E and PCNA increased with the intima thickening. Compared with balloon 14 d group, the plasma NO level increased (P＜0.01), the neointima area reduced by 59.1%(P＜0.01) and the positive expression indexes of CDK2, cyclin E and PCNA decreased by 36.1%, 46.3% and 76.2% respectively in balloon+L-Arg group (P all＜0.01). CONCLUSION:L-Arg can effectively repress intima proliferation after vascular injury, which may be associated with its inhibiting the proliferation of vascular smooth muscle cell through downregulating the excessive expression of CDK2, cyclin E and PCNA.     

Mechanism of vascular hyporeactivity induced by NO in hemorrhagic shock

AIM: To investigate the role of nitric oxide (NO) in vascular hyporeactivity during prolonged hemorrhagic shock (HS). METHODS: Anesthetized Sprague-Dawley rats (180-220 g) were subjected to HS insult in which they were bled to a mean arterial pressure (MAP) of 40 mmHg (5.33 kPa) and arteriolar reactivity to norepinephrine in spinotrapezius was detected. The constant MAP of 40 mmHg was maintained until vascular hyporeactivity had occurred and then were resuscitated or sacrificed for further analysis. NO synthase (NOS) activity was measured ex vivo by the conversion of [³H]-arginine to [³H]-citrulline in homogenates from heart, lung, liver, spleen, duodunum, skeletal muscle. 24 h survival rates of resuscitated rats were observed with and without administration of aminoguanidine (AG), a selective inducible NOS (iNOS) inhibitor. Mesenteric arteriolar smooth muscle cells (ASMC) were isolated, and the effects of L-arginine (L-Arg) on membrane potential (MP) of ASMC were determined by fluorescent probe and confocal microscopy in the absence and presence of AG. RESULTS: When vascular hyporeactivity occurred, an increase of NOS activity was observed in liver and heart. Resuscitated rats with AG had a higher survival rate compared with that of control. The MP of ASMC was decreased (more negative) immediately following the addition of L-Arg, and the hyperpolarization effects of L-Arg were partially blocked in the presence of AG. CONCLUSION: These results suggest that excessive NO produced in HS is responsible for the occurrence of vascular hyporeactivity in prolonged hemorrhagic shock, and one of the mechanisms of which may be hyperpolarization of ASMC caused by NO.     

Effect of nitric oxide on urotensin-Ⅱ expression in pulmonary arterioles of rats chronically exposed to hypoxia-hypercapnia

AIM: To investigate the roles of nitric oxide/L-arginine (NO/L-Arg) pathway and urotensin-Ⅱ (UⅡ) in the development of pulmonary hypertension induced by chronic hypoxia-hypercapnia in rats.METHODS: Forty male Sprague-Dawley rats were randomly divided into four groups (n=10): normal control group (A), hypoxia-hypercapnia+saline group (B), hypoxia-hypercapnia+L-Arg liposome group (C) and hypoxia-hypercapnia+N-nitro-L-arginine methyl ester (L-NAME) group (D).Contents of UⅡ, UⅡ mRNA and receptor of UⅡ (UT) mRNA in pulmonary arterioles were measured with immunohistochemistry analysis and in situ hybridization, respectively.Change of small pulmonary vascular microstructure was also investigated.RESULTS: (1) The mean pulmonary artery pressure (mPAP) and the weight ratio of right ventricle to left ventricle plus septum ［RV/(LV+S)］ in B and D groups were all higher than those in A group (respectively, P<0.05), with C group significantly lower than those in B group (respectively, P<0.01).(2) Light microscopy showed that the ratio of vessel wall area to total area (WA/TA) and the media thickness of pulmonary arterioles (PAMT) in B group were higher than those in A group (P<0.05), with C group significantly lower than those in B group.(3) The contents of UⅡ, UⅡ mRNA and UT mRNA in pulmonary arterioles in B and D groups were all higher than those in A group (respectively, P<0.01), while the expression of UⅡ and UⅡ mRNA in C group were lower than those in B group (P<0.01).CONCLUSION: The pathological process of pulmonary hypertension induced by chronic hypoxia-hypercapnia might be related to upregulation of UⅡ located in pulmonary arterioles, which might be partially inhibited by exogenous NO in rats.     

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.     

Effects of endogenous nitric oxide on potassium channels of bronchial smooth muscle cells from asthmatic rats

AIM: To investigate the effects of in vivo application of L-arginine on potassium channels in bronchial smooth muscle cells (BSMC) isolated from asthmatic model rats. METHODS: Male SD rats were randomly divided into control group, asthmatic group and asthmatic rats treated with L-arginine (L-Arg group). Single BSMCs were obtained by acute enzyme separation method. The resting membrane potential (Em), Ca2+-activated K+ channels (BKCa) currents and voltage-dependent K+ channel (Kv) currents in BSMCs were recorded under whole-cell patch clamp technique. RESULTS: (1) The Em of asthmatic group was significantly lower than that in control group (P<0.05). In vivo application of L-Arg significantly hyperpolarized BSMCs near to control group (P>0.05). (2) The peak current density at +50 mV of KCa: IKca in asthmatic group ［(43.8±16.5) pA/pF］ was significantly lower than that in normal group ［(72.5±19.9) pA/pF］ (P<0.01). Treatment with 300 mg/kg L-Arg significantly increased IKca in asthmatic group to (58.7±12.4) pA/pF (P<0.05). (3) The peak currents density at +50 mV of Kv: IKv in asthmatic group ［(32.4±8.7) pA/pF］ was significantly lower than that in control group ［(57.7±9.8) pA/pF］ (P<0.01). Treatment with L-Arg also significantly increased IKv in asthmatic group to (43.6±7.9) pA/pF, (P<0.05). CONCLUSION: Endogenous NO improves Em in asthmatic BSMCs, increases the activities of BKCa channels and Kv channel. These findings implicate that NO may have a potential therapeutically role in airway hypersensitivity.     

Effect of ligustrazine on cerebral injury in LPS-induced septic shock rats

AIM: To investigate the effect of ligustrazine (Lig) on cerebral injury in LPS-induced septic shock rats and to explore the underlying mechanism.METHODS: Wistar rats (n=48) were randomly divided into control group, LPS group and LPS+Lig treatment group. The rats in LPS group were randomly divided into 2 subgroups at time points of 6 h and 12 h. After ligustrazine treatment, the venous blood was collected by removal of eyeballs to detect the concentration of neuron-specific enolase (NSE) using ELISA. The nitric oxide (NO) concentration in the homogenate of brain tissues was examined. The apoptosis in the hippocampus was analyzed by TUNEL staining. The protein expression of Bax and Bcl-2 was determined by Western blot.RESULTS: Ligustrazine inhibited the elevation of NSE and NO concentrations in LPS-induced septic shock rats. Furthermore, ligustrazine administration also attenuated LPS-induced increase in Bax expression and decrease in Bcl-2 expression. CONCLUSION: Ligustrazine decreases the concentration of NSE and NO, and attenuates cerebral injury in LPS-induced septic shock rats. These effects may be related to the regulation of Bax and Bcl-2 expression.     

Mechanism of mesenteric lymph duct ligation against the renal insufficiency in hemorrhagic shock rats

AIM: To observe the effect of mesenteric lymph duct ligation on free radical and inflammatory mediator in serious hemorrhagic shock rats at different periods, and explore the mechanism of intestinal lymphatic pathway on renal insufficiency. METHODS: 78 male Wistar rats were divided into the sham group, shock group, and ligation group. The model of serious hemorrhagic shock was established in shock group, ligation group, and mesenteric lymph was blocked by ligating mesenteric lymph duct in ligation group after resuscitating. All rats were executed and kidneys were taken out for making homogenate of 10 percent to determine levels of MDA, SOD, NO, NOS, tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6) and myeloperoxidase (MPO) at time points after shock 90 min, after transfusion and resuscitate 0 h, 1 h, 3 h, 6 h, 12 h and 24 h. The expression of inducible nitric oxide synthase (iNOS) mRNA in kindey was detected by RT-PCR. RESULTS: The contents of MDA, NO, NOS, TNF-α, IL-6, MPO and iNOS expressions in renal homogenate of shock group were increased after transfusion and resuscitation, and were higher at 6 h and 12 h, and was significantly higher than that in sham group. The acvitity of SOD was significantly lower than that in sham group (P<0.01, P<0.05). The contents of MDA, NO, NOS, TNF-α, IL-6, MPO and iNOS expression in renal homogenate of ligation group after transfusion and resuscitation 6 h, 12 h and 24 h were significantly lower than those in shock group at same points, and the SOD activity was higher (P<0.01, P<0.05). CONCLUSION: The results demonstrate that the ligation of mesenteric lymph duct can antagonise the development of renal failure in serious hemorrhagic shock rats, and its mechanism might relate to reduce the PMN sequestration, decrease the levels of TNF-α and IL-6, inhibit NO production and expression of iNOS mRNA, suppress the release of free radical and consumption of SOD.     

Mesenteric lymph reperfusion exacerbates brain injury in superior mesenteric artery occlusion shock rats

AIM: To observe the effect of mesenteric lymph reperfusion (MLR) on the brain morphology and neurotransmitter in rats with superior mesenteric artery occlusion (SMAO) shock, and to explore the mechanism of oxygen free radicals, nitric oxide (NO), polymorphonuclear neutrophils (PMN), membrane ATPase function and energy metabolism. METHODS: Twenty-four male Wistar rats were randomly divided into 4 groups: in sham group, the rats were given only anesthetization and operation; in MLR group, the rats were performed 1 h occlusion of mesenteric lymphatics (ML) followed by 2 h of reperfusion; in SMAO group, the rats were performed 1 h occlusion of superior mesenteric artery (SMA) followed by 2 h of reperfusion; in MLR+SMAO group, the rats were performed 1 h occlusion of SMA and ML followed by 2 h of reperfusion. After 2 h of reperfusion, the brain tissue was taken for preparing microscopic sections to observe the morphological change. At the same time, the brain tissue was homogenized for determining the choline acetyltransferase (ChAT), acetylcholine esterase (AChE), dopamine (DA), norepinephrine (NE), lactic acid (LA), malondialdehyde (MDA), superoxide dismutase (SOD), NO, nitric oxide synthase (NOS), myeloperoxidase (MPO), cell membrane ATPase and ATP. RESULTS: Morphological observation showed that the architecture of the brain was close to normal in sham and MLR groups. Necrosis, degeneration and occasional swelling were found in neuronal cells in SMAO group, and in MLR + SMAO group the injury of the neurons was more serious than that in SMAO group. The contents of MDA, NO and LA, the activities of AChE, NOS and MPO in brain homogenate in SMAO and MLR+SMAO groups were increased, the ChAT activity and DA, NE contents were reduced significantly than those in MLR and sham groups, respectively. The contents of MDA and NO, the activities of AChE, NOS and MPO in MLR+SMAO group were higher than those in SMAO group. The activities of Na+-K+-ATPase and SOD in brain homogenate in SMAO group were lower than those in sham and MLR groups, the Mg2+-ATPase activity and ATP content were lower than those in MLR group. The activities of SOD, Na+-K+-ATPase, Ca2+-ATPase, Mg2+-ATPase and Ca2+-Mg2+-ATPase in brain homogenate in MLR+SMAO group were lower than those in sham and MLR groups, and the DA, Ca2+-ATPase, Mg2+-ATPase, Ca2+-Mg2+-ATPase and ATP were also lower than those in SMAO group. CONCLUSION: MLR exacerbates the brain injury, reduces the DA level and increases the AChE activity in SMAO shock rats, indicating that MLR enhances the brain tissue free radical injury, NO synthesis and releases, PMN detention, and decreases the activity of cell membrane ATPase, also induces the energy metabolism dysfunction.     

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.     

Effect of chronic hypoxia on L-Arginine/nitric oxide pathway in rat pulmonary artery

AIM: To study the effect of chronic hypoxia on L-Arginine/NO pathway in rat pulmonary artery. METHODS: Changes in pulmonary artery L-Arginine(L-Arg) transport, nitric oxide synthase (NOS) activity, plasma nitrite level and L-Arg level in HPH rats were investigated. RESULTS: (1) The mean pulmonary arterial pressure (mPAP) and weight ratio of right ventricle to left ventricle and septum (RV/LV+S) of HPH group were higher than those in control group (P＜0.01). (2) Plasma L-Arg level in HPH group was not significantly changed. (3) At low (0.2 mmol/L)or high(5.0 mmol/L)concentration of L-Arg, the velocity of L-Arg transport in HPH group was lower than that in control group (P＜0.05 or P＜0.01). (4) The activity of pulmonary artery tNOS, iNOS and cNOS in HPH group were increased by 38.0%, 32.8% and 53.0%, respectively (P＜0.01), compared with control group. (5) Plasma NO level of HPH group was decreased, which was negative correlation to mPAP and RV/LV+S (P＜0.01). CONCLUSION: The decrease of nitric oxide generation might result from L-Arg transport injury, while pulmonary artery tNOS, iNOS and cNOS activity were enhanced during chronic hypoxia.     

Effect of endogenous H2S on pulmonary hypertension during acute lung injury induced by LPS and its interaction with NO

AIM: To investigate the effect of H2S on pulmonary artery hypertension during acute lung injury induced by LPS and the interaction between the systems of hydrogen sulfide (H2S)/cystathionine-β-lyase (CSE) and nitric oxide (NO)/nitric oxide synthase (NOS) in this process. METHODS: Seventy-two adult male rats were randomly divided into four groups: control group, LPS group, LPS+L-NAME group and LPS+propargylglycine (PPG) group. Mean pulmonary artery pressure (mPAP) of each rat was examined at 2 h, 4 h, 6 h and 8 h after treatment. H2S and NO contents in plasma, NO content, iNOS, cNOS and CSE activity in lung were measured at 4 h or 8 h after treatment, respectively. Expression of iNOS in lung tissue was also detected by immunohistochemistry technique, and the injury of lung was evaluated with morphological changes under microscope. RESULTS: LPS could induce severe lung injury, and mPAP, NO content, iNOS activity and its protein expression in LPS group significantly increased, but cNOS activity, H2S content and CSE activity decreased compared with those of control group. Administration of L-NAME before LPS could attenuate the changes induced by LPS. Pre-administration of PPG, a CSE inhibitor, exacerbated the injury by LPS, but there was no prominent variation in cNOS activity. CONCLUSION: Reduced endogenous H2S could increase pulmonary artery hypertension during acute lung injury induced by LPS. There is a negative effect between H2S/CSE system and NO/NOS system in this process.     

Role of β-endorphin in the suppression of cellular immunity of rats following trauma-hemorrhagic shock()

AIM: To explore the role of plasma β-endorphin(β-EP) in the suppression of cellular immunity following trauma-hemorrhagic shock(T-HS). METHODS: ① Wistar rats with T-HS were sacrificed at 0 h, 1 h, 3 h, 6 h, 12 h, 24 h after T-HS. Plasma sample was collected and β-EP levels in plasma was measured. Rats with sham-operated were served as the controls. ②In in vitro experiment, splenic cells were isolated and mixed from four normal rats and cocultured with shock plasma (SP) or SP +β-EP antiserum. ConA-induced splenic cell proliferation, IL-2 production, IL-2R expression were examined. RESULTS: ① Levels of plasma β-EP elevated remarkably after T-HS immediately, peaked at 1h , showed decreasing tendency and restored normal 24 h after T-HS. ② Shock plasma significantly suppressed ConA-induced splenic cell function. Levels of plasma β-EP were negatively correlated with spenic cell proliferation and IL-2 production and IL-2R expression. Compared with SP group, splenic cell function elevated markedly in SP + β-EP antiserum group, but still lower than that in controls. CONCLUSION: The elevated plasma β-EP following T-HS was involved in the suppression of cellular immunity.     

Changes in endogenous nitric oxide and effects of inhaled nitric oxide on pulmonary artery hypertension in chronically hypoxic rats

AIM: To investigate the role of nitric oxide (NO)in the development of chronically hypoxic pulmonary artery hypertension (PAH) and the hemodynamic effects of inhaled NO on pulmonary circulation. METHODS: 67 male adult SD rats were randomly divided into 7 groups: (1) control (n=9);(2) chronically intermitent hypoxia (CIH, 6 h/d, 7 d/w) 1 week(n=7); (3) CIH 2 weeks (n=11); (4) CIH 3 weeks (n=11); (5) CIH 1 week+L-NAME (NO synthase inhibitor, 30 mg/kg, by gavage, n=10); (6)CIH 3 weeks+L-Arg (NO precursor, 10 mg/kg, by gavage, n=9); (7) CIH 3 weeks+inhaled NO (0.0004% for 20 min, n=10) to determine the mean pulmonary artery pressure (MPAP), weigh the right ventricle (R) and ventricular segment plus left ventricle (S+L), and calculate R/(S+L) (g/g) and R/Wt (Wt: body weight, g/kg). RESULTS: 1.MPAP increased compared with control when CIH 1 week, reaching the highest when CIH 2 weeks; R/(S+L) and R/Wt also increased notably when CIH 1 week (P＜0.01); 2. The level of plasma NO₂^-/NO₃^- elevated significantly when CIH 2 weeks, but fell when CIH 3 weeks; the content of plasma ET-1(endothelin-1) also increased significantly. The level of plasma ET-1 correlated with R/(S+L) and R/Wt, r=0.43 and 0.46, respectively, both P＜0.01; 3. The level of plasma NO₂^-/NO₃^- droped 33.2 % (P＜0.01) after treatment with L-NAME, with R/(S+L) increasing 15.2 % (P＜0.05); 4. L-Arg decreased the MPAP 17.8 %(P＜0.01). CONCLUSION: The endogenous NO release increases at early stage (1-2 weeks) of chronic hypoxia, but falls at the prolonged stage; the elevated level of plasma ET-1 possibly plays an important role in remodeling of chronically hypoxic pulmonary vessels and ventricle; inhaled NO significantly decreases the chronically hypoxic PAH.