Total nitric oxide production is low in patients with chronic renal disease

BACKGROUND: A deficiency of the endogenous vasodilator nitric oxide (NO) has been implicated as a potential cause of hypertension in chronic renal disease (CRD) patients. This study was conducted to determine whether 24-hour NOX (NO2 and NO3) excretion (a qualitative index of total NO production) is reduced in patients with CRD. METHODS: Measurements were made in 13 CRD patients and 9 normotensive healthy controls after 48 hours on a controlled low-NOX diet. Urine was collected over the second 24-hour period for analysis of 24-hour NOX, and cGMP and blood drawn at the completion. Plasma levels of arginine (the substrate for endogenous renal NO synthesis), citrulline (substrate for renal arginine synthesis), and the endogenous NO synthesis inhibitor asymmetrical dimethylarginine (ADMA) and its inert isomer and symmetrical dimethylarginine (SDMA) were also determined. RESULTS: Systolic blood pressure was higher in CRD patients (12 of whom were already on antihypertensive therapy) than in controls (P < 0.05). Twenty-four-hour urinary NOX excretion was low in CRD patients compared with controls despite similar dietary NO intake, suggesting that net endogenous NO production is decreased in renal disease. In contrast, the 24-hour urinary cGMP did not correlate with UNOXV. Plasma citrulline was increased in CRD patients, possibly reflecting reduced conversion of citrulline to arginine. Plasma arginine was not different, and plasma ADMA levels were elevated in CRD versus controls, changes that would tend to lower NO synthase. CONCLUSION: These results suggest that NO production is low in CRD patients and may contribute to hypertension and disease progression in CRD.     

Role of angiotensin II in the renal effects induced by nitric oxide and prostaglandin synthesis inhibition.

The objective of this study was to examine the renal effects of changes in intrarenal angiotensin II levels during the administration of a cyclooxygenase inhibitor, when nitric oxide synthesis is reduced. In the first group of dogs, the administration of meclofenamate and a subpressor dose of L-NAME induced an increase (P < 0.05) in arterial pressure (14 +/- 2 mm Hg), a decrease (P < 0.05) in RBF (180 +/- 13 to 111 +/- 10 mL/min) and GFR (37 +/- 3 to 24 +/- 5 mL/min), and a reduction in the renal excretory response to a sodium load. In the second group, the administration of a converting enzyme inhibitor prevented the increase in arterial pressure, the renal vasoconstriction, and the increase in the proximal but not the distal tubular sodium reabsorption induced by the inhibition of prostaglandins and nitric oxide synthesis. In the third group, it was found that a small increase in the intrarenal angiotensin II levels, which does not produce changes in renal function in control conditions, induced a significant decrease in RBF (183 +/- 14 to 71 +/- 12 mL/min) and GFR (36 +/- 3 to 13 +/- 4 mL/min) when meclofenamate was administered and nitric oxide synthesis was slightly reduced. The results of this study suggest that renal vasoconstriction and increased proximal sodium reabsorption during the reduction of nitric oxide and prostaglandin synthesis are produced by endogenous angiotensin II levels. These results also suggest that endogenous intrarenal nitric oxide and prostaglandins may serve as homeostatic mediators of angiotensin II effects when the intrarenal levels are inappropriately elevated, as occurs in salt-sensitive hypertension.     

Renal effects of HMG-CoA reductase inhibition in a rat model of chronic inhibition of nitric oxide synthesis

BACKGROUND/AIMS: In addition to their lipid-lowering effects, HMG-CoA reductase inhibitors (statins) induce a variety of pleiotropic actions that have been recently studied in the area of cardiovascular and renal protection. In the present studies we sought to determine whether statins retain beneficial effects in the experimental model of NO deficiency achieved by chronic administration of a pressor dose of L-arginine analogue N-nitro-L-arginine-methyl ester (L-NAME). METHODS: To address this issue, blood pressure (BP), renal function (GFR), and albuminuria were determined in rats treated for 4 weeks with L-NAME, L-NAME + atorvastatin (ATO), and in untreated controls. In addition, renal cortical protein expression of caveolin 1 (CAV1), vascular endothelial growth factor (VEGF), and activity of RhoA were also determined. RESULTS: L-NAME administration resulted in sustained elevation of BP, decreased GFR, and in higher albuminuria as compared to control animals. Co-administration of ATO with L-NAME normalized albuminuria and prevented decreases in GFR in L-NAME rats without having an impact on pressor effects of L-NAME. CAV1 protein expression was similar in all groups of rats. In contrast, VEGF expression and RhoA activity was increased in L-NAME-treated animals, and normalized with co-administration of ATO. CONCLUSION: Treatment with ATO exerts early nephroprotective effects in the NO-deficient model of hypertension. These effects could be mediated by amelioration of VEGF expression and reduction of RhoA activity.     

Protection of wistar furth rats from chronic renal disease is associated with maintained renal nitric oxide synthase

Wistar Furth (WF) rats do not develop renal injury after severe reduction of renal mass. Because clinical and animal studies suggested that nitric oxide (NO) deficiency occurs and may contribute to chronic renal disease (CRD), the status of the NO system in WF versus Sprague Dawley (SD) rats was examined with the 5/6 renal ablation/infarction (A/I) model of CRD. Eleven weeks after A/I, SD rats developed proteinuria, severe kidney damage, decreased renal function, and marked decreases in total and renal NO synthase (NOS), specifically neuronal NOS. In contrast, WF rats exhibited elevated baseline and maintained post-A/I total NO production, with no decrease in renal cortex NOS activity despite a decrease in remnant neuronal NOS abundance. When low-dose chronic Nomega-nitro-L-arginine methyl ester treatment was added for WF A/I-treated rats, rapid progression of CRD was observed. In conclusion, elevated NO production in WF rats was associated with protection from the progression of CRD after renal mass reduction. The protection might be attributable to greater total and renal NO-generating capacity and increased nephron number, compared with SD rats. NOS inhibition rendered WF rats susceptible to progression, suggesting a possible critical threshold for NO production, below which renal injury occurs.     

Locally activated renin-angiotensin system associated with TGF-beta1 as a major factor for renal injury induced by chronic inhibition of nitric oxide synthase in rats

Chronic inhibition of nitric oxide synthase (NOS) is known to cause renal parenchymal injury with systemic hypertension. To elucidate the pathogenetic mechanism in renal damage induced by NOS inhibition, N(omega)-nitro-L-arginine methyl ester (L-NAME) was given orally for 12 wk in Wistar rats, and the roles of tissue renin-angiotensin system and transforming growth factor-beta1 (TGF-beta1) were investigated. BP and urinary protein excretion increased significantly in L-NAME rats compared with control rats, and glomerulosclerosis and interstitial fibrosis developed. In L-NAME rats, the cortical tissue levels of angiotensin-converting enzyme activity and angiotensin II were significantly higher than those in control rats. The cortical mRNA expressions of both TGF-beta1 and fibronectin were significantly elevated in L-NAME rats. Immunohistochemically, increased expressions of both fibronectin and alpha-smooth muscle actin were also revealed in L-NAME rats. In L-NAME rats, these histologic injuries and the increased expression of TGF-beta1 were equally ameliorated by either angiotensin-converting enzyme inhibitor or angiotensin II type 1 receptor antagonist, but not by hydralazine. In conclusion, the locally activated renin-angiotensin system in connection with the increased TGF-beta1 expression is a major pathogenetic feature of renal injury in chronically NOS-inhibited rats.     

Iodinated contrast induced renal vasoconstriction is due in part to the downregulation of renal cortical and medullary nitric oxide synthesis

OBJECTIVES: The loss of renal function continues to be a frequent complication of the iodinated contrast agents used to perform diagnostic angiography and endovascular procedures. This study examined the hypothesis that contrast-induced renal injury is partly due to a decrease in cortical and medullary microvascular blood flow after the downregulation of endogenous renal cortical and medullary nitric oxide (NO) synthesis. METHODS: Anesthetized male Sprague-Dawley rats (300 g) had microdialysis probes or laser Doppler fibers inserted into the renal cortex to a depth of 2 mm and into the renal medulla to a depth of 4 mm. Laser Doppler blood flow was continuously monitored, and the microdialysis probes were connected to a syringe pump and perfused in vivo at 3 muL/min with lactated Ringer's solution. Dialysate fluid was collected at time zero (basal) and 60 minutes after infusion of either saline or Conray 400 (6 mL/kg). Both groups were treated with saline carrier, N(omega)-nitro-L-arginine methyl ester hydrochloride (L-NAME, 30 mg/kg), L-arginine (400 mg/kg), or superoxide dismutase (10,000 U/kg), an oxygen-derived free radical scavenger. Dialysate was analyzed for total NO and eicosanoid synthesis. The renal cortex and medulla were analyzed for inducible NO synthase (iNOS), cyclooxygenase-2 (COX2), prostacyclin synthase, and prostaglandin E(2) (PGE(2)) synthase content by Western blot analysis. RESULTS: Conray caused a marked decrease in cortical and medullary blood flow with a concomitant decrease in endogenous cortical NO, PGE(2), and medullary NO synthesis. The addition of L-NAME to the Conray further decreased cortical and medullary blood flow and NO synthesis, which were restored toward control by L-arginine. Neither L-NAME nor L-arginine (added to the Conray) altered cortical or medullary eicosanoids release. Medullary PGE(2) synthesis decreased when superoxide dismutase was added to the Conray treatment, suggesting that oxygen-derived free radicals had a protective role in maintaining endogenous medullary PGE(2) synthesis after Conray treatment. Conray did not significantly alter iNOS, COX-2, prostacyclin synthase, or PGE(2) synthase content. CONCLUSIONS: These findings suggest that the downregulation of renal cortical and medullary NO synthesis contributes to the contrast-induced loss of renal cortical and medullary microvascular blood flow. Preservation of normal levels of renal cortical and medullary NO synthesis may help prevent or lessen contrast-induced renal vasoconstriction and lessen contrast-induced renal injury found after diagnostic and therapeutic endovascular procedures.     

Plasma renin activity and the renal response to nitric oxide synthesis inhibition.

Inhibition of systemic endothelium-derived relaxing factor (EDRF) synthesis with L-Nw-nitroarginine (L-NAME) results in decreased RBF, which can be reversed by acute blockade of angiotensin II (AII). Because AII is particularly elevated in the renal circulation, it was hypothesized that the degree of renal vasoconstriction produced by L-NAME in Inactin-anesthetized rats is related to PRA. To test this, PRA was chronically increased or suppressed by the manipulation of dietary sodium (eating 0.03% sodium chow or deoxycorticosterone acetate plus drinking 1% NaCl, respectively). After 10 days, rats were anesthetized for determination of blood pressure (BP) and RBF before and after L-NAME (10 mg/kg body wt). In rats with high PRA (61.6 +/- 10.4 ng of angiotensin I [Al]/mL/h; N = 8), L-NAME increased BP by 29 +/- 2 mm Hg (from 110 +/- 4 to 139 +/- 5 mm Hg; P < 0.001), decreased RBF by 27% (from 7.9 +/- 0.3 to 5.8 +/- 0.3 mL/min/g kidney wt; P < 0.001), and increased renal vascular resistance (RVR) by 67% (from 14.5 +/- 0.9 to 24.2 +/- 1.1 resistance units [RU]; P < 0.001). When rats with high PRA (N = 8) were treated with 10 mg/kg body wt of DuP 753, on AII receptor antagonist, L-NAME similarly increased BP by 30 +/- 5 mm Hg (from 81 +/- 3 to 111 +/- 5; P < 0.001) but RBF did not change and RVR increased by only 31% (from 10.9 +/- 0.8 to 13.3 +/- 0.7 RU; P < 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)     

Oxygen-dependent inhibition of respiration in isolated renal tubules by nitric oxide.

BACKGROUND: The partial pressure (tension) of oxygen (PO2) in the kidney medulla has been established to be lower than that of the cortex. The kidney medulla has been shown to be particularly sensitive to hypoxia. However, the measured PO2 in the kidney medulla is sufficient to support maximal respiration. It has been recently shown that endogenously produced nitric oxide (NO) may inhibit oxygen consumption in the kidney. We studied whether NO plays a role in hypersensitivity of the kidney medulla to hypoxia. METHODS: We studied the effect of added NO on isolated cortical and outer medullary renal tubules in simultaneous oxygen consumption and NO measurements at different oxygen concentrations. RESULTS: We found that NO could potently and reversibly inhibit respiration at nanomolar concentrations. The inhibitory effect of NO was markedly increased at low physiological oxygen concentrations. The effect of NO was cGMP independent because the selective guanylyl cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) at a 10 microM concentration had no effect on basal or NO-inhibited respiration. The value for half-maximal NO-mediated inhibition of respiration was virtually identical to that found in isolated mitochondria, and therefore, NO was most likely directly acting on mitochondria. Interestingly, we found no differences in sensitivity to NO-mediated inhibition between outer medullary and cortical tubules. CONCLUSIONS: We suggest that because of its low PO2, the renal outer medulla is more sensitive to hypoxia, not because of the low PO2 as such, but probably because of the competition between NO and oxygen to control respiration.     

Reversal of renal lesions following interruption of nitric oxide synthesis inhibition in transgenic mice.

BACKGROUND: Renal fibrosis, a common complication of hypertension and diabetes is considered as a non-curable disease and is characterized by the abnormal accumulation of collagen I within the kidney. Chronic inhibition of nitric oxide (NO) synthesis is a model of hypertension associated with the development of nephroangiosclerosis. The present study investigated whether halt of NO inhibition leads to the regression of renal sclerotic lesions. METHODS: The NO deficiency (N(G)-nitro-L-arginine methylester; L-NAME) model of hypertension was applied in transgenic mice harbouring the luciferase reporter gene under the control of the collagen I-alpha2 chain promoter. RESULTS: Systolic pressure gradually increased following the administration of L-NAME, and reached 160 mmHg after 8-10 weeks. Activation of collagen I gene within the renal vasculature preceded the blood pressure increase and was accompanied by the appearance of sclerotic glomeruli and tubulointerstitial infiltration. After renal lesions had been established (20 weeks), animals were divided in three subgroups for an additional experimental period of 10 weeks: first group continued to receive L-NAME, in the second, L-NAME administration was stopped to allow endogenous NO synthesis and in the third the removal of L-NAME was combined with endothelin receptor antagonism. Removal of L-NAME decreased, without normalizing, systolic pressure and collagen I gene activity; renal morphology was substantially improved, and tubulointerstitial infiltration disappeared. Combination of L-NAME removal with endothelin antagonism normalized collagen I gene expression and further improved renal morphology without further decreasing blood pressure. CONCLUSION: Manipulating the balance between NO/vasoconstrictors in favour of NO could provide a curative approach against renal inflammatory and fibrotic complications associated to hypertension.     

Modulation of renal disease in MRL/lpr mice by pharmacologic inhibition of inducible nitric oxide synthase

BACKGROUND: MRL-MPJFaslpr (MRL/lpr) mice spontaneously develop lupus-like disease characterized by immune complex glomerulonephritis and overproduction of nitric oxide (NO). Blocking NO production pharmacologically by a non-specific nitric oxide synthase (NOS) inhibitor ameliorated renal disease in MRL/lpr mice while genetically deficient inducible NOS (iNOS) mice developed proliferative glomerulonephritis similar to wild-type controls.METHODS: To clarify the role of iNOS in the pathogenesis of nephritis in MRL/lpr mice, we treated mice with two different NOS inhibitors. Either NG-monomethyl-l-arginine (L-NMMA), a nonspecific NOS inhibitor, or l-N6-(1-iminoethyl)lysine (L-NIL), an iNOS specific inhibitor, was administered in the drinking water from 10 through 22 weeks of age with disease progression monitored over time. Control mice received water alone.RESULTS: Both L-NMMA and L-NIL blocked NO production effectively in MRL/lpr mice. As expected, neither L-NNMA nor L-NIL had an effect on antibody production, immune complex deposition or complement activation. Although both NOS inhibitors decreased protein excretion, L-NMMA was more effective than L-NIL. Pathologic renal disease was significantly decreased at 19 weeks in both treatment groups. At 22 weeks the L-NIL treated mice, but not the L-NMMA mice, had significantly reduced renal disease scores compared to controls.CONCLUSION: These results indicate that specific inhibition of iNOS blocks the development of pathologic renal disease in MRL/lpr mice.     

Bacterial translocation during graft-versus-host disease after small bowel transplantation is reduced following inhibition of inducible nitric oxide synthesis

BACKGROUND: Increased nitric oxide (NO) production may contribute to intestinal barrier dysfunction and increased bacterial translocation (BT). Since BT may play a major role in graft-versus-host disease (GVHD) after small bowel transplantation (SBTx), we evaluated the role of NO production in GVHD after SBTX in the rat. METHODS: Using the standard model of semiallogeneic SBTx in the rat, we prepared three experimental groups. Recipients in group 1 received LBNF1-LBNF1 transplants and were treated with aminoguanidine (AG) (200 mg/kg), recipients in group 2 received Lewis-LBNF1 grafts and were injected with saline, and recipients in group 3 received Lewis-LBNF1 transplants and AG (200 mg/kg). Urine nitrite/nitrate levels were measured daily, and BT was determined by culturing peritoneal swabs, mesenteric lymph nodes, spleen, liver, and blood. RESULTS: In group 1 we detected indefinite survival with normal histology. In group 2 a survival of 10.5 +/- 1.1 days was reached, and the typical histological features of acute GVHD were observed. The animals in group 3 showed a mean survival of 14.8 +/- 0.6 days (P<0.02 compared with group 2) and the histological features of acute GVHD, although with a prolonged time course. Comparing NO production and BT between groups 2 and 3 we detected significantly reduced NO production on postoperative days 2-9 (P<0.03) and significantly decreased BT on postoperative days 3 and 9 (P<0.03). CONCLUSION: Inhibition of inducible NO synthesis with AG reduces NO production, decreases BT, and prolongs survival during GVHD after SBTx and therefore may be a useful addition to standard treatment protocols for GVHD.     

Reciprocal expression of vascular endothelial growth factor and nitric oxide synthase by coronary arterial wall cells during chronic inhibition of nitric oxide synthesis in rats

Chronic inhibition of nitric oxide (NO) synthesis by oral administration of N(G)-nitro-L-arginine methyl ester (L-NAME) causes hypertension and produces arteriosclerosis in rats. Balloon injury induces upregulation of vascular endothelial growth factor (VEGF) in medial smooth muscle cells of the rat arterial wall, and NO secreted by a restored endothelium acts as the negative feedback mechanism that downregulates VEGF expression to basal levels. In this study, we tested the hypothesis that a reciprocal relation between VEGF and NO would be established in a rat model of chronic NO blockade. Male Wister rats received plain drinking water (n = 10) or L-NAME (0.5 mg/ml) in the drinking water (n = 11) for 6 weeks. After 6 weeks, the wall-to-lumen ratios and perivascular fibrosis in the coronary arteries were greater in the L-NAME group than in the control group. NO synthase-positive cells in the intima were abundantly observed in the control group, whereas no such cells were seen in the L-NAME group. In contrast, the number of VEGF-positive smooth muscle cells in the media was greater in the L-NAME group than in the control group. These findings strongly suggest a reciprocal relation between VEGF and NO even in a rat model of chronic NO blockade.     

Urea induces macrophage proliferation by inhibition of inducible nitric oxide synthesis.

BACKGROUND: Atherosclerosis is a major cause of morbidity and mortality in chronic renal failure and is associated with the proliferation of macrophages within atherosclerotic lesions. METHODS: Because the progression of atherosclerosis as a consequence of decreased nitric oxide synthesis has been described, we investigated the correlation between the inhibition of inducible nitric oxide synthase (iNOS) by urea, macrophage proliferation as assayed by cell counting, tritiated thymidine incorporation and measurement of cell protein, and macrophage apoptosis. RESULTS: Urea induces a dose-dependent inhibition of inducible nitric oxide synthesis in lipopolysaccharide-stimulated mouse macrophages (RAW 264.7) with concomitant macrophage proliferation. Macrophage proliferation, as determined by cell counting, became statistically significant at 60 mM urea, corresponding to a blood urea nitrogen level of 180 mg/100 ml, concentrations seen in uremic patients. iNOS protein expression showed a dose-dependent reduction, as revealed by immunoblotting when cells were incubated with increasing amounts of urea. The decrease of cytosolic DNA fragments in stimulated macrophages incubated with urea shows that the proliferative actions of urea are associated with a decrease of NO-induced apoptosis. CONCLUSIONS: Our data demonstrate that the inhibition of iNOS-dependent NO production caused by urea enhances macrophage proliferation as a consequence of diminished NO-mediated apoptosis.     

Circulating endothelial nitric oxide synthase inhibitory factor in some patients with chronic renal disease

BACKGROUND: Chronic renal disease (CRD) is associated with hypertension and reduced synthesis of nitric oxide (NO). Here, we investigated whether there is a circulating endothelial NO synthase (eNOS) inhibitory factor(s) in some patients with CRD that might directly influence endothelial NOS. METHODS: Human dermal microvascular endothelial cells (HDMECs) were incubated for six hours with 20% plasma from subjects with normal renal function (PCr = 0.8 +/- 0.2 mg%), and patients with moderate renal insufficiency of various causes (PCr = 4.0 +/- 1.5 mg%) and impact on NOS activity, transport of L-arginine, and abundance of eNOS protein were measured. Plasma concentrations of asymmetric and symmetric dimethyl L-arginine (ADMA and SDMA) were also measured. RESULTS: There was no effect of any human plasma on L-arginine transport. The NOS activity was variable in CRD patients and fell into two subgroups: CRD I, individual values similar to control, and CRD II, individual values lower than control mean. The effect of CRD plasma on NOS activity in cultured cells was not related to the primary disease, but was predicted by plasma ADMA levels since plasma ADMA was elevated in CRD II versus both control and CRD I. Blood urea nitrogen and creatinine levels were uniformly elevated in CRD plasma. The abundance of eNOS protein was unaffected by plasma. CONCLUSION: High plasma levels of ADMA in CRD patients are independent of reduced renal clearance, suggesting an alteration in ADMA synthesis and/or degradation. High ADMA is a marker and is partly responsible for the inhibition of eNOS activity in cultured cells and may also result in reduced eNOS activity in vivo, with consequent hypertension.     

Reduced nitric oxide synthase activity in rats with chronic renal disease due to glomerulonephritis

BACKGROUND: Animal studies with systemic nitric oxide synthase (NOS) inhibition and renal ablation, suggest that NO deficiency is both a cause and a consequence of chronic renal disease (CRD). METHODS: This study examined a glomerulonephritis (GN) model of CRD to determine if NO is deficient. In addition to measuring indices of renal function (proteinuria, creatinine clearance, structural damage), indices of total and renal nitric oxide production also were assessed (total NO(X) excretion, renal NOS activity, renal NOS protein abundance, plasma levels of NOS substrate and endogenous inhibitor). RESULTS: Rats developed increasing proteinuria 12 to 20 weeks after induction of GN (with anti-glomerular basement membrane, GBM, antibody) and at 20 weeks exhibited reduced creatinine clearances and increased glomerulosclerosis relative to age-matched controls. Total NO(X) excretion was reduced and the renal cortical NOS activity and neuronal NOS (nNOS) abundance was decreased relative to controls. There was no impact on renal or aortic endothelial NOS expression or cerebellar nNOS. The plasma l-arginine (Arg) concentration was well maintained but plasma asymmetric dimethylarginine (ADMA) concentration increased in GN versus control animals. CONCLUSIONS: Total and renal NOS activity is reduced in the GN model of CRD due to increased circulating endogenous NOS inhibitors and decreased renal nNOS abundance.     

Neuroprotection by selective inhibition of inducible nitric oxide synthase after experimental brain contusion

The inflammatory response is thought to be important for secondary damage following traumatic brain injury (TBI). The inducible nitric oxide synthase (iNOS) isoform is a mediator in inflammatory reactions and may catalyze substantial synthesis of NO in the injured brain. This study was undertaken to analyze neuronal degeneration and survival, cellular apoptosis and formation of nitrotyrosine following treatment with the iNOS-inhibitor L-N-iminoethyl-lysine (L-NIL) in a model of brain contusion. A brain contusion was produced using a weight-drop device in 30 rats. The animals received treatment with L-NIL or NaCl at 15 min and 12 h after the injury and were sacrificed at 24 h or 6 days after trauma. iNOS activity was measured at 24 h post-trauma by the conversion of L-[U- ( 14 )C]arginine to L-[U-( 14 )C]citrulline and immunohistochemistry for iNOS. Peroxynitrite formation was indirectly assessed by nitrotyrosine (NT) immunohistochemistry. Neuronal degeneration and survival were assessed by Fluoro-Jade (FJ) and NeuN stainings, and cellular death by TUNEL staining. iNOS activity but not iNOS immunoreactivity was significantly reduced in animals that received L-NIL. Neuronal degeneration (FJ) and NT immunoreactivity were significantly reduced at 24 h. Neuronal survival was unchanged at 24 h but increased at 6 days in L-NIL-treated animals. Cellular apoptosis of ED-1 and NeuN positive cells was significantly reduced following L-NIL treatment at 6 days after trauma. We demonstrated neuroprotection by selective inhibition of iNOS after trauma. L-NIL appeared to protect the injured brain by limiting peroxynitrite formation. Our findings support a putative harmful role of iNOS induction early after TBI.     

ACE inhibition reduces glomerulosclerosis and regenerates glomerular tissue in a model of progressive renal disease

Today angiotensin II inhibition is primarily used to slow the rate of progression of kidney diseases. There is evidence that these therapies can induce a partial regression of glomerular lesions. However, we do not know yet the extent of sclerotic lesion regression and whether new glomerular tissue is formed to help support the renal function. We used male Munich Wistar Fromter (MWF) rats, an experimental model for progressive kidney disease, to quantify kidney structural lesions upon angiotensin-converting enzyme (ACE) inhibition therapy. Animals were studied at 50 weeks of age, when renal function and structure are severely altered, and after a 10-week observation period, without or with treatment with lisinopril (80 mg/l in drinking water). A group of untreated Wistar rats was used as controls. With age, proteinuria, and serum creatinine worsen, but lisinopril almost normalized proteinuria and stabilized serum creatinine. Serial section analysis of whole glomerular tufts showed that at baseline, glomerulosclerosis affected the entire glomerular population, and that these changes further increased with age. Lisinopril significantly reduced incidence and extent of glomerulosclerosis, with the presence of glomerular tufts not affected by sclerosis (23% of glomeruli). Glomerular volume was not significantly affected by treatment, and glomerular mass spared from sclerosis increased from 46.9 to 65.5% upon treatment, indicating consistent regeneration of glomerular tissue. Lisinopril normalized baseline glomerular transforming growth factor-beta and alpha-smooth muscle actin overexpression, and prevented worsening of interstitial changes. Hence, ACE inhibition, which is widely used in human kidney disease, may not only halt the progression of renal failure, but also actually induce the regeneration of new renal tissue.     

肾皮质电灼所致大鼠实验性慢性肾衰竭动物模型的研制

目的本文基于国外学者JaneBoudet的方法改制,我们用。肾皮质电灼的方法制作大鼠实验性慢性肾衰竭模型。本文探讨成模时间、模型生化学及病理学特征等。方法Wistar种大鼠18只,雌雄各半,体质量（100±15）g。造模方法参照JaneBoudet报道的方法改制,以932型电热烧灼器替代其特制16孔针。点刺烧灼肾的上下极、前后两面除肾蒂以外的所有皮质部分。前后两次烧灼点的间距约1mm。一周后,切除右侧肾脏。观察血清肌酐、尿素氮、24h尿蛋白定量、肾脏病理组织学及透射电镜等。结果第二次手术后10-70d,造模大鼠血肌酐、尿素氮均显著升高。尿蛋白持续增加。第二次手术后70d,肾脏外观肥厚,包曼囊囊腔增大、脏层上皮细胞肿胀增生,有蛋白样沉积物形成,典型者呈新月体或环状体样。肾小球局灶、节段或全球硬化。肾小管畸形扩张、囊性变或萎缩。结论本造模方法较肾部分切除的造模方法相对安全。模型可重复性好、制备需时较短,血尿素氮、血肌酐于二次手术后10d即明显升高,据此可以认为此时模型即告成功。其后反复检测血清尿素氮、血肌酐值稳定。该模型的病理特征与人慢性肾衰竭的病理特征基本符合。因此,该模型是成功的大鼠慢性肾衰竭动物模型。     

Lipopolysaccharide impairs endothelial nitric oxide synthesis in rat renal arteries

BACKGROUND: Impaired endothelium-dependent vasodilation may contribute to hypoperfusion and failure of abdominal organs, including the kidneys during endotoxin or septic shock. In this study, the short-term (2 h) effects of bacterial lipopolysaccharide (LPS) on endothelium-dependent vasodilation in rat renal and superior mesenteric arteries were documented. METHODS: Rat renal and mesenteric arteries were dissected and exposed in vitro to LPS for two hours. The effects of LPS on vascular reactivity were determined and compared with time-matched controls. Endothelial nitric oxide (NO) release was determined using an NO microsensor in adjacent vessel segments. RESULTS: LPS impaired maximal acetylcholine (ACh)-induced endothelium-dependent vasodilation in renal arteries (62.5 +/- 8.8% vs. 34.4 +/- 7.5% in controls and LPS-exposed arteries), but not in mesenteric arteries. LPS did not alter the sensitivity of renal arteries to exogenous NO. ACh-dependent vasodilation was abolished after blocking NO synthesis with 10-4 mol/L L-NA in control and LPS-incubated renal arteries. When compared with controls, NO release induced by ACh and the receptor-independent calcium ionophore A23187 was significantly decreased (P < 0.05) in LPS-exposed renal segments and was fully abolished in endothelium-denuded segments, indicating that LPS attenuated receptor-dependent as well as receptor-independent endothelial NO release. In contrast, ACh- and A23187-induced NO release was normal in LPS-exposed mesenteric arteries. CONCLUSIONS: These results indicate that LPS-induced selective impairment of ACh-induced endothelium-dependent relaxation in rat renal arteries is caused by decreased endothelial NO release. This may contribute to the propensity for acute renal failure during septic shock.