The effects of Na movement on surgical myocardial protection: the role of the Na+-H+ exchange system and Na-channel in the development of ischemia and reperfusion injury.

OBJECTIVES: We investigated whether the Na+-H+ exchange inhibitor, HOE642 (Hoe), and/or the Na channel blocker, mexiletine (Mex), enhance a cardioprotective effect on St. Thomas' Hospital cardioplegic solution (STS) to clarify the mechanism by which intracellular Na+ is accumulated after cardioplegic arrest. MATERIALS AND METHODS: Isolated working rat hearts were perfused with Krebs-Henseleit bicarbonate buffer (KHBB). The hearts were then arrested with STS and subjected to normothermic global ischemia (30 min). This was followed by Langendorff reperfusion (15 min) and then a working reperfusion (20 min). In study A, we added Hoe (5, 10, and 20 microM), Mex (70 microM), or a combination of Hoe (20 microM) and Mex (70 microM), to STS. In study B, we added Hoe (20 microM), Mex (70 microM), or a combination of Hoe (20 microM) and Mex (70 microM) to KHBB during the first 3 min of Langendorff reperfusion. RESULTS: In study A, the addition of Hoe (10 and 20 microM) to STS showed a significantly greater postischemic recovery of cardiac output compared to the control group [63.1+/-5.7% (10 microM), 62.7+/-4.7% (20 microM), and 55.5+/-4.6% (control), respectively]. The postischemic recovery of cardiac output was significantly greater in the group of the combined addition (Hoe and Mex) to STS than that in the control, 20 microM Hoe, 70 microM Mex groups [70.3+/-3.7 (Hoe and Mex), 55.5+/-4.6% (control), 62.7+/-4.7% (Hoe 20 microM), and 60.2+/-4.7% (Mex 70 microM), respectively]. The myocardial water content in the postischemic period was 565.1+/-29.1, 525.8+/-2.9, 509.4+/-19.6, and 532.2+/-20.1; it was 497.3+/-9.1 mL/100 g dry weight in the control; and 10 microM Hoe, 20 microM Hoe, and 70 microM Mex in the combined use groups. In study B, there was no significant difference in the postischemic recovery of cardiac output in all experimental groups. CONCLUSION: The combined use of the Na+-H+ exchange inhibitor and Na+ channel blocker during cardioplegia may achieve a superior cardioprotective effect on myocardial damage because of ischemia and reperfusion.     

The effects of Na+ -H+ exchange inhibitor, KB-R9032, administered at the time of reperfusion in perfused rat heart

BACKGROUND: We have reported that pretreatment with KB-R9032, a newly developed Na+ -H+ exchange inhibitor is protective against reperfusion-induced ventricular arrhythmia in the isolated perfused rat heart. This study was conducted to elucidate whether the drug is equally effective when it is given at the time of reperfusion. METHODS: Male Wistar rat hearts (n=32, 16 for each group) were perfused by means of Langendorff technique. Each heart was subjected to regional ischemia (occlusion of the left anterior descending coronary artery for 11 minutes) and to three minutes of reperfusion (release of the occlusion). KB-R9032 4 mg (one shot group) or a vehicle without drug (control) were given 30 seconds before the reperfusion to 30 seconds after the reperfusion. RESULTS: In the control group reperfusion-induced ventricular fibrillation (VF) occurred in 91.7% and the duration was 165 +/- 14.4 seconds, but, in one shot group, the incidence of VF decreased to 6.3% and the duration of VF was reduced to 0.4 +/- 0.4 seconds, respectively (P<0.05 vs control group). CONCLUSIONS: It has been shown in this study that the Na+/H+ exchange inhibitor KB-R9032 given at the time of reperfusion suppresses reperfusion arrhythmias in the ischemia-reperfusion model of isolated rat heart.     

Blood cardioplegic protection in profoundly damaged hearts: role of Na+-H+ exchange inhibition during pretreatment or during controlled reperfusion supplementation

BACKGROUND: Inhibition of the Na+/H+ exchanger before ischemia protects against ischemia-reperfusion injury, but use as pretreatment before blood cardioplegic protection or as a supplement to controlled blood cardioplegic reperfusion was not previously tested in jeopardized hearts. METHODS: Control studies tested the safety of glutamate-aspartate-enriched blood cardioplegic solution in 4 Yorkshire-Duroc pigs undergoing 30 minutes of aortic clamping without prior unprotected ischemia. Twenty-four pigs underwent 30 minutes of unprotected normothermic global ischemia to create a jeopardized heart. Six of these hearts received normal blood reperfusion, and the other 18 jeopardized hearts underwent 30 more minutes of aortic clamping with cardioplegic protection. In 12 of these, the Na+/H+ exchanger inhibitor cariporide was used as intravenous pretreatment (n = 6) or added to the cardioplegic reperfusate (n = 6). RESULTS: Complete functional, biochemical, and endothelial recovery occurred after 30 minutes of blood cardioplegic arrest without preceding unprotected ischemia. Thirty minutes of normothermic ischemia and normal blood reperfusion produced 33% mortality and severe left ventricular dysfunction in survivors (preload recruitable stroke work, 23% +/- 6% of baseline levels), with raised creatine kinase MB, conjugated dienes, endothelin-1, myeloperoxidase activity, and extensive myocardial edema. Blood cardioplegia was functionally protective, despite adding 30 more minutes of ischemia; there was no mortality, and left ventricular function improved (preload recruitable stroke work, 58% +/- 21%, p < 0.05 versus normal blood reperfusion), but adverse biochemical and endothelial variables did not change. In contrast, Na+/H+ exchanger inhibition as either pretreatment or added during cardioplegic reperfusion improved myocardial recovery (preload recruitable stroke work, 88% +/- 9% and 80% +/- 7%, respectively, p < 0.05 versus without cariporide) and comparably restored injury variables. CONCLUSIONS: Na+/H+ exchanger blockage as either pretreatment or during blood cardioplegic reperfusion comparably delays functional, biochemical, and endothelial injury in jeopardized hearts.     

Sodium-hydrogen exchange inhibition attenuates in vivo porcine myocardial stunning

BACKGROUND: Inhibition of the sodium-hydrogen exchanger isoform 1 with HOE-642 (cariporide) has been shown to protect against ischemia-reperfusion injury and to decrease myocardial cell death in numerous animal preparations; however the effects of cariporide in stunned myocardium are not as well understood. We sought to determine whether cariporide attenuated myocardial stunning in vivo. METHODS: Open chest anesthetized pigs (22-33 kg) were subjected to 15 min of left anterior descending coronary artery (LAD) occlusion followed by 3 h of reperfusion. Regional ventricular function was assessed by segment shortening. Contractility was measured by stroke work and by load-insensitive preload recruitable stroke work and preload recruitable stroke work area. Vehicle or HOE-642 (1 mg/kg, IV) was administered 10 min before LAD occlusion. RESULTS: Cariporide treatment significantly improved postischemic segment shortening, stroke work, preload recruitable stroke work, and preload recruitable stroke work area and had no systemic hemodynamic effects. After 3 h of reperfusion, control animals recovered 33% +/- 4% and 33% +/- 3% of preischemic LAD segment shortening and preload recruitable stroke work area values, respectively, whereas animals treated with HOE-642 recovered 59% +/- 6% and 57% +/- 6%, respectively (p < 0.05). Seven (39%) of 17 control animals exhibited ventricular fibrillation during reperfusion; none of the cariporide-treated pigs fibrillated. CONCLUSIONS: Sodium-hydrogen exchange inhibition can attenuate postischemic myocardial stunning in addition to its well-described anti-infarct properties. Inhibition of the sodium-hydrogen exchanger may be beneficial in patients susceptible to postischemic myocardial dysfunction associated with cardiac surgery.     

ANP inhibits Na(+)-H+ antiport in proximal tubular brush border membrane: role of dopamine

Infusion of ANP to rats results in an inhibition of Na(+)-H+ antiport and Na(+)-Pi symport in brush border membrane vesicles (BBMV) prepared from kidneys of these animals (J Clin Invest 75:1983). iIn the present study we investigated the intrarenal mechanism by which infused ANP elicits these changes in proximal tubular transport systems. As in rats, infusion of ANP to rabbits resulted in a diuresis, natriuresis, and increase in GFR; however, unlike in rats, the fractional excretion of phosphate (Pi) was not changed. In BBMV prepared from cortices of ANP-infused rabbits, the rate of Na(+)-H+ antiport was decreased (delta -27%), but Na+ gradient-dependent uptakes of Pi and L-proline were not different from controls. Incubation of rabbit cortical tubule suspension in vitro with ANP 10(-7) M alone had no inhibitory effect on Na(+)-H+ antiport in BBMV prepared from these tubules, whereas incubation with other hormonal agents, 1 U/ml PTH (delta 61%) or with dopamine (DA) 10(-4) M (delta -34%), did inhibit the rate of Na(+)-H+ antiport in BBMV from the same pool of tubules. However, when tubules were incubated in the presence of (10(-5) M) DA, the addition of 10(-7) M ANP did cause a significant (delta -21%) decrease in Na(+)-H+ antiport activity in BBMV. In contrast, ANP did not show similar inhibitory effect in the presence of submaximal inhibitory doses of PTH. To explore whether ANP may act on proximal tubules in vivo indirectly, via mediation of DA, we evaluated the effect of ANP on some parameters of catecholamine system in vivo.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ischemic preconditioning and Na+/H+ exchange inhibition improve reperfusion ion homeostasis

BACKGROUND: Intramyocyte sodium (Na+) increases during ischemia and reperfusion, which causes myocardial calcium (Ca2+) uptake and leads to myocyte injury or death. This study determines if ischemic preconditioning and myocyte sodium-hydrogen ion (Na+-H+) exchange (NHE) inhibition decreases Na+ gain that otherwise occurs with cardioplegic arrest and reperfusion. METHODS: Pigs had 1 hour of cardioplegic arrest followed by reperfusion. Group 1 had no intervention (controls). Group 2 received dimethyl amiloride (DMA, an NHE inhibitor), and group 3 had ischemic preconditioning before cardioplegic arrest. Precardioplegia to postreperfusion change in intramyocyte ion content was measured with atomic absorption spectrometry. The time to initial electrical activity and number of defibrillations needed to establish an organized rhythm postreperfusion were used as electrophysiologic variables to measure ischemia-reperfusion injury. RESULTS: Intramyocyte Na+ content for group 1 increased from 45.9+/-6.7 to 61.9+/-22.5 micromol/g (p = 0.02). Group 2 had an insignificant decrease in intramyocyte Na+ of 27.7+/-19.58 micromol/g (p = 0.06), and group 3 had an insignificant decrease of 10.8+/-46.33 micromol/g (p = 0.48). Interstitial water increased significantly in all groups, but there were no significant increases in intramyocyte water content. Electrophysiologic recovery was similar for all three groups. CONCLUSIONS: The NHE inhibition and ischemic preconditioning each eliminated the increase in intramyocyte Na+ content that otherwise occurred with cardioplegic arrest and reperfusion in this porcine model. Because their mechanisms are distinct, it is possible that an additive beneficial effect against ischemia-reperfusion injury can be achieved by using NHE inhibition together with a preconditioning stimulus as prereperfusion therapy.     

Propofol increases myofilament Ca2+ sensitivity and intracellular pH via activation of Na+-H+ exchange in rat ventricular myocytes

BACKGROUND: The objectives were to determine the extent and mechanism of action by which propofol increases myofilament Ca2+ sensitivity and intracellular pH (pHi) in ventricular myocytes. METHODS: Freshly isolated adult rat ventricular myocytes were used for the study. Cardiac myofibrils were extracted for assessment of myofibrillar actomyosin adenosine triphosphatase (ATPase) activity. Myocyte shortening (video edge detection) and pHi (2',7'-bis-(2-carboxyethyl)-5(6')-carboxyfluorescein, 500/440 ratio) were monitored simultaneously in individual cells field-stimulated (0.3 Hz) and superfused with HEPES-buffered solution (pH 7.4, 30 degrees C). RESULTS: Propofol (100 microM) reduced the Ca2+ concentration required for activation of myofibrillar actomyosin ATPase from pCa 5.7 +/- 0.01 to 6.6 +/- 0.01. Increasing pHi (7.05 +/- 0.03 to 7.39 +/- 0.04) with NH4Cl increased myocyte shortening by 35 +/- 12%. Washout of NH4Cl decreased pHi to 6.82 +/- 0.03 and decreased myocyte shortening to 52 +/- 10% of control. Propofol caused a dose-dependent increase in pHi but reduced myocyte shortening. The propofol-induced increase in pHi was attenuated, whereas the decrease in myocyte shortening was enhanced after pretreatment with ethylisopropyl amiloride, a Na+-H+ exchange inhibitor, or bisindolylmaleimide I, a protein kinase C inhibitor. Propofol also attenuated the NH4Cl-induced intracellular acidosis, increased the rate of recovery from acidosis, and attenuated the associated decrease in myocyte shortening. Propofol caused a leftward shift in the extracellular Ca2+-shortening relation, and this effect was attenuated by ethylisopropyl amiloride. CONCLUSIONS: These results suggest that propofol increases the sensitivity of myofibrillar actomyosin ATPase to Ca2+ (ie., increases myofilament Ca2+ sensitivity), at least in part by increasing pHi via protein kinase C-dependent activation of Na+-H+ exchange.     

Regulation of the renal Na+-H+ exchanger by protein phosphorylation

Starting from observations in intact cells and extending to studies in native membranes and solubilized membrane proteins, a significant body of evidence has been accumulated to indicate that some of the short-term regulatory influences on the Na+-H+ exchanger in the apical membrane of the proximal convoluted tubule act via protein phosphorylation mediated by specific protein kinases. Protein phosphorylation mediated by PKA inhibits the Na+-H+ exchanger while that mediated by PKC stimulates activity. The effect of PKA and PKC on the Na+-H+ exchanger in native membranes and in solubilized brush border membrane proteins appears to be consistent with most of the published observations in intact cells. Further studies using solubilized, renal brush border membrane proteins indicated that protein phosphorylation mediated by CaM-kinase II inhibited the activity of the Na+-H+ exchanger. The physiologic significance of this observation in intact cells remains to be determined. It is hoped that the types of experimental approaches outlined in this review will yield additional insights into the structure of the Na+-H+ exchanger and to a clearer understanding of its physiologic regulation.     

The roles of cell Ca2+, protein kinase C and the Na(+)-H+ antiport in the development of hypertension and insulin resistance.

There is evidence that the cytosolic free Ca2+, protein kinase C, and the Na(+)-H+ antiport cross-communicate with one another through positive and negative feedback mechanisms, thereby maintaining cellular Ca2+ and pH homeostasis. This triumvirate may play a role in the development of insulin resistance--a common characteristic of both essential hypertension and non-insulin-dependent diabetes mellitus. Circulating cells from patients with essential hypertension and non-insulin-dependent diabetes mellitus demonstrate elevated cytosolic free Ca2+, increased protein kinase C activity, or both, and these perturbations are associated with augmented activity of the Na(+)-H+ antiport. If present in other cells (e.g., striated muscle cells and adipocytes), these alterations could underlie insulin resistance in essential hypertension and non-insulin-dependent diabetes mellitus.     

核因子kappaB在早期心肌缺血再灌注损伤中的作用

目的 探讨核因子(NF)-κB在心肌早期缺血再灌注损伤中的作用。方法将18只山羊随机分为单纯体外循环(CPB)组、缺血再灌注(IR)组、缺血再灌注加特异性NF-κB抑制剂二硫代氨基甲酸吡咯烷(PDTC)组。建立山羊CPB模型,心脏行缺血60 min,恢复血流再灌注90 min,PDTC组在心肌缺血前应用PDTC(100 mg／kg)。于心肌再灌注后,测量血流动力学数据及测定局部心功能,并应用脱氧核苷酸末端转移酶介导的缺口末端标记(TUNEL)法染色检测心肌细胞凋亡数量,同时采用凝胶电泳迁移率(EMSA)法检测心肌组织中NF-κB的含量。结果 缺血再灌注能引起典型心肌缺血损伤的组织学改变,IR组NF-κB在缺血心肌组织中大量激活,心肌组织中NF-κB的活性水平显著高于CPB组(P<0.05);而PDTC组再灌注60、90min后,NF-κB的核转录活性明显减弱,显著低于IR组(P<0.05);IR和PDTC组中心肌细胞凋亡指数分别为(11.2±0.4)％和(6.4±0.2)％,心肌损伤显著减轻(P<0.05)。结论NF-κB在心肌早期缺血再灌注损伤中起重要作用,PDTC通过抑制NF-κB的核转录活性,从而减轻了心肌缺血再灌注损伤。     

Effects of Na(+)-HCO3- symport on ischemia/reperfusion injury; Na+/H+ exchanger inhibitor and buffer composition

We studied the impact of perfusate buffer composition on the relative degree of protection afforded by Na+/H+ exchanger (NHE) inhibition during ischemia as opposed to during reperfusion. Isolated rat hearts were perfused with bicarbonate- or HEPES-buffered medium. There was infusion of HOE 694 immediately before ischemia, during initial reperfusion, or during both of these periods. With bicarbonate-buffered medium, HOE 694 improved the post-ischemic recovery of left ventricular developed pressure (LVDP) when given before ischemia and before ischemia plus during reperfusion. In the presence of HEPES-buffered medium, however, HOE 694 significantly improved recovery of LVDP in all protocols. HOE 694 also provided an almost complete recovery of LVDP (88 +/- 9% vs 30 +/- 7% in controls) when given before ischemia plus during reperfusion. In conclusion, our results suggest that the influence of NHE activity during reperfusion on the extent of functional recovery is modulated significantly by perfusate buffer composition.     

Na+/H+ exchange inhibition and antioxidants lack additive protective effects after reperfusion injury in the working heterotopic rat heart isograft.

BACKGROUND: The utility of combining strategies of myocardial protection was studied in intact rat hearts subjected to 1 hour of ischemia and 40 minutes blood reperfusion. METHODS: Lewis rats (n = 48) were divided into 4 transplant groups. Twenty-four hearts were arrested by coronary perfusion with hypothermic Celsior solution at 60 mm Hg. The aortic valve was punctured to introduce volume into the left ventricle (LV), and the hearts were abdominally isografted. Animals were either given both the antioxidant probucol (300 mg/kg) and the sodium-hydrogen exchange inhibitor cariporide (5 mg/kg) (CP; n = 6), just cariporide (CAR; n = 6), just probucol (PROB; n = 6), or neither drug (CON; n = 6). After 40 minutes of blood reperfusion, transplanted hearts were rearrested. The control recipients' native hearts (native; n = 6) were also arrested. Postmortem LV compliance relations and myocardial water content (MWC) were measured. RESULTS: Grafts protected by probucol were significantly more compliant than controls and significantly less compliant than grafts protected by cariporide alone and with both cariporide and probucol (p = 0.0001, analysis of variance). Compliance relations for CP overlapped those for CAR. All grafts were less compliant than natives. MWC was significantly greater in controls and PROB than in natives. CONCLUSIONS: Pretreatment with cariporide in the setting of ischemia-reperfusion injury provides greater protection against the development of diastolic abnormalities than probucol when Celsior solution is used for both arrest and preservation. In this model, there is no advantage to combining the drugs, supporting the hypothesis that there is an overlapping mechanism of protection.     

Na+/H+ exchange inhibition improves post-transplant myocardial compliance in 4-hour stored donor hearts

Na⁺/H⁺ exchange inhibitors have cardioprotective properties. The effects of the new Na⁺/H⁺ exchange inhibitor, HOE642 on myocardial function were assessed after transplantation of canine brain-dead and non-brain-dead donor hearts preserved for 4 h. Four groups were studied: brain-dead donors; non-brain-dead donors; brain-dead donors and recipients treated with HOE642 (2 mg/kg); and treated non brain-dead donors and recipients. Donor hearts were stored in NIH2. At the end of 60 min reperfusion after transplantation, pressure–volume curves were constructed. Biopsies were analysed histologically and ultrastructurally. Afterwards, weaning from cardiopulmonary bypass was accomplished. HOE642 improved compliance in hearts from both brain-dead and non-brain-dead donors. No differences in myocardial water content nor in myocardial performance were detected. No irreversible damage was seen ultrastructurally. It is concluded that myocardial compliance after transplantation was improved by administration of HOE642. The use of this inhibitor might improve the current myocardial preservation technique for transplantation.     

The Role of Na+-H+ Exchanger Isoform 1 in Aldosterone-Induced Glomerulosclerosis in Vivo

Aldosterone is reported to promote fibrosis of multiple organs. Recent studies showed that Na⁺-H⁺ exchanger isoform 1 (NHE1) was involved in mineralocorticoid-induced tissue fibrosis. The present study examined the role of NHE1 in aldosterone-induced glomerulosclerosis in rats. SD male rats were subjected to 5/6 nephrectomy and divided into four groups: rats subjected to sham operation were used as control (SHAM group), 5/6 nephrectomy (SNX group), SNX treated with aldosterone via osmotic mini-pump (ALDO group), and SNX treated with aldosterone plus NHE1 inhibitor 5-(N, N-Dimethyl) amiloride hydrochloride (DMA) (ALDO+DMA group). The rats were sacrificed at the 12th week. We found that aldosterone treatment significantly increased kidney weight/body weight ratio and systolic blood pressure compared with SNX rats. Aldosterone also increased proteinuria and serum creatinine level. The NHE1 antagonist DMA significantly reversed the effect of aldosterone on proteinuria, but had no effect on the aldosterone associated hypertension and the elevation of serum creatinine. The remnant kidney of 5/6 nephrectomized rats exhibited increased glomerulosclerosis score, tubulointerstitial fibrosis, and tubular proteinaceous cast, which were significantly enhanced by aldosterone treatment. DMA treatment significantly reduced aldosterone-associated glomerulosclerosis, but failed to improve aldosterone-induced tubulointerstitial fibrosis and tubular proteinaceous cast. The aldosterone-induced increase in renal TGFβ1 and PCNA was significantly prevented by treatment with DMA. Our data showed that NHE1 inhibitor reduced aldosterone-induced glomerulosclerosis but not hypertension in 5/6 nephrectomized rats. The present study suggested that NHE1 contributed to aldosterone-induced-glomerulosclerosis and could be a potential therapeutic target for chronic kidney disease.     

Effect of diabetes on cytosolic free Ca2+ and Na(+)-K(+)-ATPase in rat aorta.

We examined Na(+)-K(+)-ATPase activity and the levels of alpha I-, alpha II-, and beta-subunit mRNA and protein in aortic cells of diabetic rats. Diabetes was induced by streptozocin. Na(+)-K(+)-ATPase activity was significantly reduced on the 2nd day of diabetes (9.4 +/- 1.3 vs. 17.5 +/- 2.1 mumol NADH.mg-1 protein.h-1, P less than 0.05) and remained depressed on days 7 and 14. The levels of 5.3-kilobase (kb) mRNA band of the catalytic alpha II-subunit of Na(+)-K(+)-ATPase were also decreased on the 2nd day of diabetes, whereas the second band, 3.4 kb, was not affected. Both bands were significantly decreased on days 7 and 14. This was followed by a reduction in the levels of alpha II-protein (day 14). The levels of alpha I- and beta-subunit mRNA and alpha I- protein were not affected by diabetes. A decrease in Na(+)-K(+)-ATPase activity was accompanied by a significant (P less than 0.001) increase in the cytosolic free Ca2+ concentrations [( Ca2+]i) in diabetic aortic cells (221 +/- 18 nM on the 7th day and 242 +/- 17 nM on the 14th day vs. 153 +/- 7 nM in controls). These findings are consistent with the hypothesis that decreased Na(+)-K(+)-ATPase activity and gene expression in vascular smooth muscle cells with accompanied rises in [Ca2+]i may be an important pathogenetic factor in the development of hypertension and atherosclerosis in diabetes.     

肝门阻断再灌注后脑钠素和心肌细胞膜Na+-K+ATPase活性的改变

目的 观察肝门阻断再灌注后血流动力学和心肌能量代谢改变.方法 大鼠气管切开机械通气.随机分为假手术对照组(A组,n=24):不作肝血流的阻断;肝血流阻断组(B组,n=24):阻断肝十二指肠韧带60 min后开放再灌注;门静脉转流下肝血流阻断组(C组,n=24):分别阻断肝左中叶及右叶肝蒂,保留尾叶血供作为门静脉血液回流通道,60 min后再灌注.每组各有8只大鼠分别于再灌注前、再灌注后1、6 h取材.血气分析研究肝门阻断期间门脉中pH值和电解质变化、ELISA检测脑钠素(BNP)水平以及比色法测定心肌细胞膜Na -K ATPase活性.结果 与A组比较,B组再灌注前pH值显著降低,K 升高幅超过1倍(P＜0.01),再灌注后开始下降,Ca2 也进行性下降;同时再灌注后B组肺动脉压(PAP)显著升高,6 h后仍不能恢复;B组BNP再灌注后高于A组(P＜0.05),但组内比较差异无统计学意义;再灌注后B组心肌Na -K ATPase活性显著降低(P＜0.01).结论 肝门阻断后再灌注可引起脑钠素和心肌细胞膜Na -K ATPase活性改变.     

NHE-1反义基因磁性纳米颗粒的构建及鉴定

目的　构建NHE 1反义基因磁性纳米颗粒 ,探讨以氧化铁磁性纳米颗粒为载体转染NHE 1反义基因治疗肿瘤的可能性。方法　应用共沉淀法制备外包葡聚糖的氧化铁磁性纳米颗粒(dextrancoatedironoxidenanoparticles ,DCIONP)。使用透射电镜和激光粒度检测仪检测DCIONP的形态和粒径 ,采用琼脂糖凝胶电泳分析氧化铁磁性纳米颗粒结合NHE 1反义基因及抵抗DNaseⅠ消化的能力 ,采用磁场吸引的方法分析氧化铁磁性纳米颗粒携带NHE 1反义基因定向运动的能力。结果　透射电镜观察显示 :纳米颗粒形状不规则 ,颗粒内部有一氧化铁的核心。激光粒度检测仪检测证实DCIONP的平均直径在 4 7nm左右。结合实验的琼脂糖凝胶电泳显示 ,pll DCIONP在各种质量比均有良好的DNA结合能力。DNA保护实验显示从质量比 0 .5∶1开始pll DCIONP能有效保护DNA不被DNaseⅠ降解。沉淀实验证明pll DCIONP可携带质粒DNA在外加磁场作用下在液体中定向移动。结论　成功构建了NHE 1反义基因磁性纳米颗粒 ,该颗粒具有粒径小、稳定性高及磁靶向运动的特点。