Effects of nitric oxide synthase inhibitors on focal cerebral ischemic injury in rats

AIM:To observe the effects of nitric oxide and different isoforms of nitric oxide synthase inhibitors on the focal cerebral ischemic injury in rats. METHODS:After the rat model of focal cerebral ischemia were established with middle cerebral artery occlusion (MCAO), aminoguanidine(AG)and N^G-nitro-L-arginine(L-NA )were administrated and the cerebral infarct size, NO production,MDA content, nitric oxide synthase(NOS) and SOD activities in the focal ischemic brain tissues were examined. RESULTS:AG could significantly attenuate the focal cerebral ischemic injury, and L-NA had a protective effect when it was administrated at 1 h,6 h but not at 3 h after surgery.CONCLUSION:Cerebral ischemic injury could be attenuated by both selective and nonselective inhibition of NOS.     

Effect of ginsenoside Rg1 on activity and protein expression of NOS in rats with cerebral ischemic reperfusion injury

AIM: To observe the neuroprotective effects of ginsenoside Rg1 on focal cerebral ischemia reperfusion (I/R) injury in rats. METHODS: SD rats were applied to right middle cerebral artery occlusion (MCAO) for 2 h followed by 24 h of reperfusion. The rats were randomly divided into sham-operation group, I/R group and ginsenoside Rg1 pretreatment groups. The rats in ginsenoside Rg1 pretreatment groups were pretreated with ginsenoside Rg1 at doses of 10, 20 or 40 mg/kg once a day for 7 days and then subject to MCAO. The neurological deficit score was measured by Longa's method. The neurons were observed with Nissel staining. The nitric oxide (NO) content, the activity of nitric oxide synthase (NOS) and inducible NOS (iNOS) in the brain tissues were determined. The expression of neuronal NOS(nNOS) and iNOS was detected by Western blotting. RESULTS: Compared with sham-operation group, ginsenoside Rg1 significantly reduced the neurological deficit score and increased the neuron number in the hippocampus. The activity of NOS and iNOS, and NO content were decreased. Ginsenoside Rg1 also down-regulated the expression of nNOS and iNOS. CONCLUSION: Ginsenoside Rg1 has protective effect on the brain during cerebral I/R injury in rats. The mechanism may be related to reducing the content of NO and the activiy of NOS dose-dependently.     

Effects of Salvia miltiorrhiza Bunge.f.alba. on mitochondrial damage and apoptosis induced by cerebral ischemia and reperfusion

AIM: To observe the effects of Salvia miltiorrhiza Bunge.f.alba. (Sal) on the mitochondrial ultra-structure, oxidative stress and apoptosis induced by ischemia injury in a rat model of focal cerebral ischemia and reperfusion.METHODS: The middle cerebral artery occlusion/reperfusion (MCAO/R) rat model was established by a modified Longa occlusion method. Adult male SD rats were randomly divided into control group, simple ischemia reperfusion group, Sal with ischemia reperfusion group and butylphthalide with ischemia reperfusion group. To study the protective effects of Sal and its mechanism, the intervention of Sal was given and the ultra-structure of mitochondria, functions of mitochondria under oxidative stress and the incidence of apoptosis of brain cells were determined.RESULTS: Many electron dense toxic granulation and vacuolus in mitochondria were observed in the rat brain of focal cerebral ischemia and reperfusion. Under the condition of ischemia and reperfusion, the mitochondria membrane was disaggregative, and the tubular cristae of mitochondrion disappeared. MDA content was obviously increased and the activity of glutathione peroxidase decreased significantly. The apoptosis of brain cells were observed in a great quantity. The changes of ultra-structure of mitochondria and the activity of GSH-Pxase were significantly improved by the treatment of Sal. Furthermore, treatment with Sal delayed the decrease of GSH-Pxase activity, and inhibited the increase in MDA content in brain tissue after ischemia and reperfusion. The incidence of apoptosis of brain cells was also decreased.CONCLUSION: Sal protects the brain tissue from ischemia injury.     

Effect of cerebral ischemic preconditioning on NOS activity and NO content in the CA1 region of the hippocampus in rats

AIM: To explore the role of NO in the induction of brain ischemic tolerance (BIT) by observing changes of NOS activity and NO2-/NO3- content following a transient cerebral ischemia. METHODS: The rat 4-vessel occluding brain ischemic model was used. 140 male Wistar rats were divided into sham, cerebral ischemic preconditioning (CIP), ischemic insult and CIP+ischemic insult groups. An occlusion of the 4 vessels for 3 min was normally used as CIP, and a relative long one for 10 min was used as ischemic insult. When CIP was followed by ischemic insult, the interval between them was 3 d. The CA1 region of the hippocampus of rats was dissected out at 0 h, 2 h, 16 h, 24 h, 36 h, 72 h and 7 d after the last time of ischemia to assay its NOS activity and NO2-/NO3- content. RESULTS: The NOS activity and NO2-/NO3- content began to increase at 16 h, peaked at 24 h and decreased to basal level at 36 h of reperfusion after CIP. The duration of the up-regulation of NOS activity and NO2-/NO3- content was much shorter than that of BIT, which usually takes place 1-7 d after CIP. The pattern of upregulation of the NOS activity and NO2-/NO3- content was similar to the CIP group, but the maximum (24 h) was much more than that in CIP group (P<0.05). In the CIP＋ischemic insult group, the NOS activity and NO2-/NO3- content increased at 2 h of reperfusion, but the maximum (24 h) were much lower than that in ischemic insult group (P<0.05). CONCLUSION: A moderate increase in NOS activity and NO production after CIP might participate in the induction of BIT by triggering a series of cellular signal transduction. In addition, inhibiting effect of CIP on over-production of NO caused by ischemic insult might be another way to induce BIT.     

Changes of serum levels of nitric oxide and nitric oxide synthase in patients during liver transplantation

AIM: To study the changes of serum levels of nitric oxide (NO) and nitric oxide synthase (NOS) in patients during liver transplantation. METHODS: Samples were obtained from 30 patients in end liver disease at five time points during liver transplantation. NO level and NOS activity were measured by radioimmunoassay and colorimetry, respectively. Arterial and mixed venous blood samples used for blood gas analysis were taken at the same time. Intrapulmonary shunt (Qs/Qt) was calculated according to the standard formula. The hemodynamics parameters including continuous cardic output (CO), HR, MABP, CVP, SVR were measured during liver transplantation. RESULTS: (1) NO2-/NO3- level at 10 min before anhepatic period was significantly higher than the baseline level. Compared with NO2-/NO3- level at 10 min before anhepatic period, NO2-/NO3- level at 30 min after anhepatic period was significantly decreased. NO2-/NO3- level at 30 min after neohepatic period was significantly higher than the baseline level and at 30 min after anhepatic period. (2) No significant change of tNOS activity was observed. Compared with the baseline activity of inducible nitric oxide synthase (iNOS), the activity at 10 min before anhepatic period and at 30 min after neohepatic period was significantly increased. The activity at 30 min after neohepatic period was significantly higher than that at 30 min after anhepatic period. (3) MABP decreased significantly when opening the inferior vena cava. CO and CVP decreased in the anhepatic stage and increased in the reperfusion stage. SVR increased during anhepatic stage and decreased significantly during neohepatic period. (4) Qs/Qt decreased significantly during anhepatic stage and increased significantly at 30 min after neohepatic period. CONCLUSIONS: Serum level of NO and NOS activity are significantly changed during liver transplantation. High level of NO may result in low systemic vascular resistance and increasing in intrapulmonary shunt.     

Effects of external counterpulsation on nitric oxide system in myocardial infarction canines

AIM:To investigate the effects of external counterpulsation(ECP)on nitric oxide(NO)and nitric oxide synthase(NOS)and the expression of NOS gene in myocardial infarction canines.METHODS:Nineteen healthy dogs were randomly divided into three groups ie.controls, ischemia group, ischemia and ECP group.Serum NO concentrations and myocardium NO levels and NOS specific activity were determined by modified nitrate reductase method.T he protein synthesis of sub-type NOS including inducible NOS(iNOS)and endothelial NOS(eNOS)of myocardial tissue were also determined by immunohistochemical method.The constitutive NOS(cNOS)mRNA was measured via in situ hybridization.RESULTS:120 and 180 minutes after the ligat ing of LAD, serum NO concentration in ECP groups were higher than those in ischemic groups(P<0.05).The NO levels and NOS specific activity in myocardium of ischemic dogs were lower than those in controls and ECP group(P<0.05).Protein synthesis of iNOS increased and that of eNOS decreased in ischemic myocardium.But ECP could control the protein synthesis of iNOS, and increase that of eNOS.Further studies showed that the expression of cNOS mRNA decreased in ischemic myocardial tissue, ECP might promote the expression of it and regulate NOS in the gene level.CONCLUSION:The results suggested that it was one of the most important mechanisms through raising the NO levels to protect ischemic myocardium in ECP.     

Dynamic changes of the concentration of nitric oxide in ischemic myocardium and its mechanism

AIM: The study was undertaken to explore the dynamic changes of the concentration of nitric oxide(NO) in ischemic myocardium and its mechanism.METHODS: In vivo myocardial ischemia of mice and in vitro perfused isolated heart of rat were used in the experiment. The effects of severity and time of ischemia on NO production, NOS activity and mRNA were examined, respectively. RESULTS: There was a considerable difference (P<0.01) in the concentration of NO between ischemia group [(9.12±1.40) μmol/L] and control group [(20.16±1.67) μmol/L] after Pit(30 U/kg) administration, and the concentration of NO of ischemic group significantly decreased [(9.17±1.33) μmol/L] compared with control group [(19.90±1.95) μmol/L] after 30 minutes of ischemia. Also, the concentration of NO after Pit(20 U/L) administration in K-H and 15 min of ischemia was (15.41±2.00) μmol/L and (15.09±2.00) μmol/L respectively in vitro, significantly lower than control group [(23.83±2.33) μmol/L and (23.63±2.52) μmol/L]. In addition, compared with control group, the number of NOS positive cells, NOS activity as well as mRNA expression in atrial muscle and ventricular muscle of ischemic group were markedly reduced, respectively. CONCLUSION: Myocardial ischemia could reduced the NO level in myocardium, down-regulation of NOS mRNA could be the possible mechanism.     

Effect of hyperbaric oxygen on gelatinase,nitric oxide synthase and the permeability of brain blood barrier in cerebral ischemia-reperfusion mice

AIM:To investigate the effect of hyperbaric oxygen (HBO) on gelatinase,nitric oxide synthase and the permeability of brain blood barrier(BBB) in ischemia-reperfusion(I/R) mice.METHODS:Using cerebral I/R models, during the reperfusion period, 0.25 MPa (ATA) HBO were applied 5 times. matrix metalloproteinase(MMP)-2,9, nitric oxide synthase(NOS) and evans blue (EB) in brain were measured.RESULTS:①HBO had significanty effect on MMP-9, but had little effect on MMP-2. ② HBO decreased the activity of NOS.③ The maxium amount of EB in IR group was at 4 hours after reperfusion and gradually decreased at 11 h, 23 h,48 h, 72 h.CONCLUSION:HBO may decrease the activities of MMP-9,NOS and the permeability of BBB in cerebral ischemia-reperfusion mice.     

Effects of ischemic postconditioning on cerebral ischemia/reperfusion injury in rats

AIM: To study the effects of ischemic postconditioning on cerebral ischemia following middle cerebral artery occlusion in rats. METHODS: 21 rats were randomly divided into three groups: middle cerebral artery occlusion (MCAO), MCAO+transient unilateral common carotid artery occlusion (u-CCA-O), MCAO+transient bilateral common carotid artery occlusion (b-CCA-O)(n=7, respectively). u-CCA-O/b- CCA-O was generated by transient middle cerebral artery occlusion plus transient unilateral/bilateral common carotid artery (CCA) occlusion. After the suture was removed, ischemic postconditioning was performed by occluding CCA for 10s, reperfusion 10s, and then allowing for another 4 cycles of 10s of reperfusion and 10s of CCA occlusion. Rats were sacrificed 2 d later and infarct size was measured. Cerebral blood flow (CBF) was measured in different 15 time points: 0 min, 10 min, 1 h after MCA occlusion, 0 min after MCA reperfusion, 10s of CCA occlusion and 10s of CCA reperfusion in all five cycles, 30 min after MCA reperfusion. Functional neurological outcome was determined 1 h and 48 h after reperfusion. Infarct volume was measured 48 h after reperfusion. RESULTS: The infarct volumes in u-CCA-O group and b-CCA-O group diminished compared to the control group. The results of CBF demonstrated that b-CCA-O group diminished 9% compared with control and u-CCA-O group when 30 min after intervention. The rats in u-CCA-O and b-CCA-O group had better neurological performance at 1 h after reperfusion. CONCLUSION: Ischemic postconditioning reduces infarct size, improves functional neurological outcome, most plausibly by diminishing cerebral blood flow.     

Knockdown of Atg5 aggravates cerebral ischemia and reperfusion injury in mice

AIM: To study the role of autophagy-related gene 5 (Atg5) in cerebral ischemia and reperfusion injury in mice. METHODS: BALB/c male mice (weighing 18~22 g) were randomly divided into sham group, ischemia/reperfusion (I/R) group, Atg5 siRNA group and control siRNA group. Focal cerebral ischemia was performed using the method of middle cerebral artery occlusion (MCAO) for 60 min and reperfusion for 24 h. In siRNA group and control group, 5 μL Atg5 siRNA or scrambled siRNA was administered by intracerebroventricular injection 24 h before MCAO. The expression of Atg5 at mRNA and protein levels in ischemic cortex at 24 h after reperfusion was determined by real-time PCR and Western blot. The infarct volume and edema were evaluated by TTC staining, and motor deficits were evaluated by neurological scoring. RESULTS: The expression of Atg5 at mRNA and protein levels was significantly increased 24 h after reperfusion in I/R group compared with sham group. Atg5 siRNA obviously decreased the expression of Atg5 at mRNA and protein levels induced by I/R. Inhibition of Atg5 exacerbated the infarct volume and ameliorated the neurological symptoms. CONCLUSION: Atg5 has neuroprotective effect on focal cerebral ischemia and reperfusion injury.     

Changes of cortisol content in plasma and hippocampus after focal cerebral ischemia-reperfusion in rats

AIM: To investigate the relationship between glucocorticoid (Gc) and injury of hippocampus neurons and the effect of Gc on dementia episode after cerebral ischemia-reperfusion. METHODS: The rat model of middle cerebral artery occlusion (MACO) was established. Cortisol contents in hippocampus and plasma of the model rats were examined by means of the radioimmunoassay at 2 h, 6 h, 12 h, 24 h after reperfusion. RESULTS: The levels of cortisol content in model group were significantly higher than those in sham group and normal group both in hippocampus and plasma. The highest cortisol content was observed at 6 hours after reperfusion. HE staining showed that the impairment of hippocampus neurons was aggravated progressively with reperfusion interval elongating. CONCLUSION: The increased cortisol in hippocampus and plasma, after 2 h cerebral ischemia and 24 h reperfusion, could aggravate the injury of hippocampus neurons and lead to dementia post stroke.     

Protective effect of spermine on rats with acute cerebral ischemia/reperfusion injury

AIM: To study the effects and the possible mechanisms of exogenous spermine on the rats with acute transient focal cerebral ischemia/reperfusion (I/R) injury.METHODS: The rat model of focal cerebral ischemia/reperfusion was established by middle cerebral artery occlusion (2 h) and reperfusion (2 h). Healthy adult SD rats were divided into 5 groups;sham group,I/R group and spermine(4,20 and 40 mmol/L)groups.The degree of cerebral injury was evaluated by neurological deficit score, infracted volume, superoxide dismutase (SOD) activity and malondialdehyde (MDA) content. The morphological changes of the brain were observed by HE staining and electron microscopy. RESULTS: Compared with I/R group, the neurological deficit score, infracted volume and the content of MDA were decreased, the SOD activity was increased and the ultrastructural changes were improved in spermine-treated groups. CONCLUSION: Exogenous spermine has a protective effect against acute focal cerebral ischemia/reperfusion injury. The mechanisms may be related to scavenging free radical by spermine.     

Glutamate transport across blood brain barrier after transient global ischemia/reperfusion in rats

AIM: to study the change of glutamate(Glu) transport across blood brain barrier(BBB) in rat following forebrain ischemia/reperfusion. METHODS: BBB unidirectional transfer constant(K_i) for [³H]-Glu in rat hippocampus, cerebral cortex and striatum were determined after rats were subjected to cerebral ischemia 10 min (two-carotid occlusion plus hypovolemic hypotension) followed by 0.17, 2, 6 and 24 h of reperfusion. The recovery of [³H]-Glu in cerebrum was also determined after intracerebral injection of [³H]-Glu in another experiment. RESULTS: Compared with control rat brain, K_i for [³H]-Glu significantly(P＜0.05) decreased at 10 min cerebral ischemia followed by 0.17, 2 and 6 h of reperfusion. At 5 min after intracerebrally injecting [³H]-Glu, recovery of [³H]-Glu in control rat brain was 23.83%. The result indicted that there is a Glu efflux mechanism on BBB. This efflux was not significantly inhibited by pretreatment of 200 mg/L probenecid. After 10 min cerebral ischemia followed by 2 h of reperfusion, the recovery(13.13%) was significantly lower than contro(P＜0.05), its recovery was only 55% of the control. The result indicated that cerebral ischemia/reperfusion may enhanced the efflux of [³H]-Glu from brain. CONCLUSION: Cerebral ischemia/reperfusion significantly reduced Glu BBB transport from plasma to brain and enhanced efflux of Glu from brain.     

Inhibitive action of atorvastatin on NADPH oxidase-derived superoxide anion in ischemic brain tissue after reperfusion in rats

AIM: Reactive oxygen species, specifically superoxide anion formed during the early phase of reperfusion, augment neuronal injury. The present study tested the hypothesis that atorvastatin protects against cerebral infarction via inhibition of NADPH oxidase-derived superoxide anion in transient focal ischemia. METHODS: Transient focal ischemia was created in halothane-anesthetized adult male Sprague-Dawley rats by middle cerebral artery occlusion (MCAO). Atorvastatin (Liptor) was administrated subcutaneously 3 times before MCAO. Infarct volume was measured by triphenyltetrazolium chloride staining. NADPH oxidase enzymatic activity and superoxide anion levels were quantified in both ischemic core and penumbral regions by lucigenin (5 μmol/L)-enhanced chemiluminescence. The expression of NADPH oxidase membrane subunit gp91phox, membrane-translocated subunit p47phox and small GTPase Rac-1 were determined by Western blotting analyses. RESULTS: NADPH oxidase activity and superoxide anion levels increased following reperfusion and peaked within 2 h of reperfusion in the penumbra, but not in the ischemic core in MCAO rats. Atorvastatin pretreatment prevented this increases, blunted the expression of membrane subunit gp91phox and prevented the translocation of cytoplasmic subunit p47phox to the membrane in the penumbra 2 h after reperfusion. CONCLUSION: These results indicate that atorvastatin protects against cerebral infarction via inhibition of NADPH oxidase-derived superoxide anion in ischemic brain tissue after reperfusion partly.     

Effects of bFGF on neuronal apoptosis and fractalkine expression in cerebral ischemia/reperfusion rats

AIM: To study the effects of basic fibroblast growth factor (bFGF) on neuronal apoptosis and fractalkine expression in ischemic penumbra after cerebral ischemia/reperfusion in rats.METHODS: Thirty-six rats were randomly divided into 3 groups: sham operation group, ischemia/reperfusion group and bFGF group. The model of middle cerebral artery occlusion was established by the method of intraluminal filament blockage. The middle cerebral arteries were blocked for 1 h and then reperfused for 24 h. Neurological performances of all rats were scored with Bederson's standard. The brain tissues of the rats were stained and the average infarct volume was calculated. TUNEL method was used to determine the number of apoptotic neurons, and the expression of fractalkine was detected by the method of immunohistochemistry.RESULTS: The score of neurological performances in bFGF group was 2.23±0.59, lower than that in ischemia/reperfusion group (3.18±0.65). The number of apoptotic neurons in bFGF group (13.22±1.35) was lower than that in ischemia/reperfusion group (17.28±1.01, P<0.05), which was the lowest in sham operation group (0.91±0.65). Compared with sham operation group, the expression of fractalkine in ischemia/reperfusion group was decreased. The expression of fractalkine in bFGF group was mainly higher than that in ischemia/reperfusion group (P<0.05).CONCLUSION: Up-regulation of fractalkine may be one of the molecular mechanisms of bFGF to protect neurons against ischemia/reperfusion injury.     

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.     

Protective effect of sCR1-SCR15-18 on cerebral ischemia/reperfusion injury in rat via inhibition of complement

AIM: To explore the effect of complement on the cerebral ischemia/reperfusion injury in rat and the protection by sCR1-SCR15-18. METHODS: 75 male SD rats were randomly divided into three groups: sham operation group (SO, n=15), middle cerebral artery occlusion and reperfusion (MCAO) without treatment group (I/R, n=30); MCAO treated with sCR1-SCR15-18 group (sCR1-SCR15-18, n=30). After the MCAO for 2 h, then reperfusion for 24 h, the scores of neural behavioral functional deficits were determined. Infarction area was measured by TTC staining. Activity of MPO in cerebral cortex was detected. C3b deposition and pathological change were observed by immunohistochemial staining and HE staining, respectively. RESULTS: After reperfusion for 24 h, the neurological deficits score, infarction area and activity of MPO in sCR1-SCR15-18 group were decreased compared to I/R group. In sCR1-SCR15-18 group, C3b deposition in ischemic area was decreased and pathological injury was improved compared to I/R group. CONCLUSION: Complement plays a role in cerebral ischemia-reperfusion injury and sCR1-SCR15-18 exerts a protective effect by inhibiting the excessive activation of complement.     

Expression of calcium sensing receptor during ischemia/reperfusion myocardial damage and relationship between CaSR and injury of myocardium

AIM: To investigate the expression of calcium sensing receptor(CaSR) during myocardial injury induced by ischemia/reperfusion and disclose the relationship between CaSR and myocardial ischemia/reperfusion. METHODS: The experimental model was established by the 30 min ligating and 1 h, 2 h, 4 h, 6 h reperfusing the left descending coronary artery (LAD) in rats. Wistar rats were randomly divided into 5 groups: sham group, ischemia/reperfusion 1 h, 2 h, 4 h, 6 h groups (I/R 1 h, 2 h, 4 h, 6 h group). CaSR mRNA expression was detected by RT-PCR. Left ventricular function was recorded. The levels of plasma lactate dehydrogenase (LDH), alondialdehyde (MDA) and superoxide dismutase (SOD) were measured. The change of ultrastructure in the ischemia/reperfusion myocardium of rats was observed by electron microscopy. RESULTS: LVSP,±dp/dtmax and SOD activity decreased gradually with the reperfusion time prolonged. LDH and MDA peaked at 2 h. The ultramicro-structural injury at the 1 h and 2 h was more serious than that at 4 h and 6 h. The expression of CaSR increased significantly after reperfusion of 1 h and 2 h, and decreased after 4 h and 6 h. CONCLUSION: The increased expression of CaSR mRNA and serious injure of myocardium were observed. CaSR may be associated with the myocardial ischemia/reperfusion injury.     

Alterations of nitric oxide synthase in cardiac sarcoplasmic reticulum from rats with myocardial calcification

AIM: To study alterations of nitric oxide synthase (NOS) in cardiac sarcoplasmic reticulum from rats with myocardial calcification, and to explore the mechanism of inhibition of SR function in the rats with myocardial calcification. METHODS: Compared with control, myocardial calcium content in the 6 weeks increased by 408%（Ｐ＜0.01）, the NO production, NOS activity and NOS protein expression in the SR with myocardial calcification increased versus control（Ｐ＜0.01）.Myocardial calcium content was not alterations significantly, but the NOS/NO pathway in the SR was up-regulated slightly in the 2 weeks. RESULTS: Compared with control, myocardial calcium content in the 6 weeks increased by 408%(P＜0.01), the NO production, NOS activity and NOS protein expression in the SR with myocardial calcification increased versus control(P＜0.01).Myocardial calcium content was not alterations significantly, but the NOS/NO pathway in the SR was up-regulated slightly in the 2 weeks. CONCLUSION: The up-regulated NOS/NO system in the SR with myocardial calcification is the important mechanism of function inhibition of the SR.