NF-kappaB inhibitors stabilize the mRNA of high-affinity type-2 cationic amino acid transporter in LPS-stimulated rat liver

BACKGROUND: Induction of inducible nitric oxide synthase (iNOS) results in nitric oxide (NO) overproduction during endotoxemia. Cellular uptake of L-arginine, modulated by the isozymes of type-2 cationic amino acid transporters (CAT), including CAT-2, CAT-2A and CAT-2B, has been reported to be a crucial factor in the regulation of iNOS activity. We sought to elucidate the expression of CAT-2 isozymes and the role of nuclear factor-kappaB (NF-kappaB) in this expression in lipopolysaccharide (LPS)-treated rat liver. METHODS: Adult male Sprague-Dawley rats were randomly given intravenous (i.v.) injections of normal saline (N/S), LPS, LPS preceded by an NF-kappaB inhibitor (PDTC, dexamethasone or salicylate) or an NF-kappaB inhibitor alone. After injection, rats were sacrificed at different times and enzyme expression and liver injury were examined. Hepatic and systemic NO production were also measured. RESULTS: CAT-2, CAT-2A and CAT-2B were constitutively expressed in un-stimulated rat liver. LPS stimulation not only significantly increased iNOS mRNA and NO concentrations but also decreased the mRNA concentrations of CAT-2 and CAT-2B, but not CAT-2A, in a time-dependent manner. LPS-induced hepatic and systemic NO overproduction was associated with hepatocellular injury. Pre-treatment with NF-kappaB inhibitors significantly attenuated LPS-induced iNOS induction as well as CAT-2/CAT-2B mRNA destabilization, which was associated with significant inhibition of NO biosynthesis and less liver injury. CONCLUSION: NF-kappaB inhibitors stabilize CAT-2 and CAT-2B mRNA in LPS-stimulated rat liver. The hepatic CAT-2/CAT-2B pathway may be a constitutive part of cytoprotective mechanisms against sepsis.     

NF-kappaB involvement in the induction of high affinity CAT-2 in lipopolysaccharide-stimulated rat lungs

BACKGROUND: Endotoxemia stimulates nitric oxide (NO) biosynthesis through induction of inducible NO synthase (iNOS). Cellular uptake of L-arginine, the sole substrate for iNOS, is an important mechanism regulating NO biosynthesis by iNOS. The isozymes of type-2 cationic amino acid transporters, including CAT-2, CAT-2A, and CAT-2B, constitute the most important pathways responsible for trans-membrane L-arginine transportation. Therefore, regulation of CAT-2 isozymes expression may constitute one of the downstream regulatory pathways that control iNOS activity. We investigated the time course of enzyme induction and the role of nuclear factor-kappaB (NF-kappaB) in CAT-2 isozymes expression in lipopolysaccharide-(LPS) treated rat lungs. METHODS: Adult male Sprague-Dawley rats were randomly given intravenous injections of normal saline (N/S), LPS, LPS plus NF-kappaB inhibitor pre-treatment (PDTC, dexamethasone, or salicylate), or an NF-kappaB inhibitor alone. The rats were sacrificed at different times after injection and enzyme expression and lung injury were examined. Pulmonary and systemic NO production were also measured. RESULTS: LPS co-induced iNOS, CAT-2, and CAT-2B but not CAT-2A expression in the lungs. Furthermore, NF-kappaB actively participated in LPS-induction of iNOS, CAT-2, and CAT-2B. LPS induced pulmonary and systemic NO overproduction and resulted in lung injuries. Attenuation of LPS-induced iNOS, CAT-2, and CAT-2B induction significantly inhibited NO biosynthesis and lessened lung injury. CONCLUSION: NF-kappaB actively participates in the induction of CAT-2 and CAT-2B in intact animals. Our data further support the idea that CAT-2 and CAT-2B are crucial in regulating iNOS activity.     

Platonin attenuates LPS-induced CAT-2 and CAT-2B induction in stimulated murine macrophages

BACKGROUND: Platonin, a cyanine photosensitizing dye, is a potent immunomodulator that suppresses acute inflammation. Platonin not only inhibits interleukin (IL)-1beta, IL-6, and tumor necrosis factor (TNF)-alpha production but also improves circulatory failure in septic rats. In addition, platonin reduces plasma nitric oxide (NO) formation during sepsis. However, the effects of platonin on inducible NO synthase (iNOS) and cationic amino-acid transporter (including CAT-2, CAT-2 A, and CAT-2B) expressions during sepsis remain uninvestigated. METHODS: Five groups of confluent murine macrophages (RAW264.7 cells) were randomly allocated to receive a 1-h pretreatment of one of five doses of platonin (0.1 microM, 1 microM, 10 microM, 100 microM, or 1000 microM) followed by lipopolysaccharide (LPS; 100 ng ml(-1)). For negative, positive, and platonin control, three other groups of cell cultures were randomly allocated to receive phosphate-buffered saline, LPS, or platonin (1000 microM). The cultures were harvested after exposing them to LPS for 18 h or a comparable duration in those groups without LPS. NO production, L-arginine transport, and expression of the relevant enzymes were then evaluated. RESULTS: Platonin significantly attenuated LPS-induced up-regulation of iNOS expression and NO production in stimulated murine macrophages in a dose-dependent manner. Platonin also significantly inhibited up-regulation of CAT-2 and CAT-2B expression as well as L-arginine transport in LPS-stimulated murine macrophages in a dose-dependent manner. In contrast, CAT-2 A expression in murine macrophages was not affected by LPS and/or platonin. CONCLUSIONS: Platonin attenuates NO production and L-arginine transport in LPS-stimulated murine macrophages possibly through inhibiting iNOS, CAT-2, and CAT-2B expression.     

Catecholamines' enhancement of inducible nitric oxide synthase-induced nitric oxide biosynthesis involves CAT-1 and CAT-2A

Catecholamines enhance inducible nitric oxide synthase (iNOS) expression that results in nitric oxide (NO) overproduction in lipopolysaccharide (LPS)-stimulated macrophages. L-arginine transport mediated by cationic amino acid transporters (including CAT-1, CAT-2, CAT-2A, and CAT-2B) is crucial in regulating iNOS activity. We sought to assess the effects of catecholamines on L-arginine transport and CAT isozyme expression in stimulated macrophages. Confluent RAW264.7 cells were cultured with LPS with or without catecholamines (epinephrine or norepinephrine, 5 x 10(-6) M) for 18 h. NO production, L-arginine transport, and enzyme expression were determined. Our data revealed that LPS co-induced iNOS, CAT-2, and CAT-2B expression, whereas CAT-1 and CAT-2A expression remained unaffected. Significant increases in NO production and L-arginine transport (approximately eight-fold and three-fold increases, respectively) were found in activated macrophages. Catecholamines significantly enhanced NO production and L-arginine transport (approximately 30% and 20% increases, respectively) in activated macrophages. Catecholamines also enhanced the expression of iNOS, CAT-1, and CAT-2A but not CAT-2 or CAT-2B in LPS-stimulated macrophages. Furthermore, the enhancement effects of catecholamines were inhibited by either dexamethasone or propranolol. We provide the first evidence to indicate that L-arginine transport in activated macrophages could be enhanced by catecholamines. Furthermore, this catecholamine-enhanced L-arginine transport might involve CAT-1 and CAT-2A but not CAT-2 or CAT-2B.     

L-Arginine transport is augmented through up-regulation of tubular CAT-2 mRNA in ischemic acute renal failure in rats

BACKGROUND: Ischemic acute renal failure (iARF) is associated with increased nitric oxide (NO) production during the reperfusion period, as endothelial nitric oxide synthase (eNOS) is maximally activated, and renal tubular inducible NOS (iNOS) is stimulated. Increased NO production leads to augmented tubular injury, probably through the formation of peroxynitrite. l-Arginine (l-Arg), the only precursor for NO, is transported into cells by cationic amino acid transporters, CAT-1 and CAT-2. We hypothesized that the increased NO production observed in iARF may result from increased l-Arg uptake, which would be reflected in the augmented expression of l-Arg transporter(s). METHODS: Ischemic acute renal failure was induced in rats by right nephrectomy + left renal artery clamping for 60 minutes. l-Arg uptake was examined in freshly harvested glomeruli and tubuli from control, sham operated, and animals subjected to 15, 30, and 60 minutes, and 24 hours of reperfusion, following 60 minutes of ischemia. Using RT-PCR, renal tissues were examined further for the expression of iNOS, CAT-1, CAT-2, arginase I and arginase II. RESULTS: Tubular expression of iNOS mRNA was initiated by ischemia, continued to increase after 60 minutes of reperfusion, and decreased after 24 hours. l-Arg transport into glomeruli was similar in all experimental groups. l-Arg uptake into tubuli was markedly augmented following the 60-minute reperfusion, while it moderately increased after 24 hours of reperfusion. This was accompanied by a parallel, preferential increase in tubular CAT-2 mRNA expression at 60 minutes of reperfusion. CAT-1 mRNA expression was unchanged, as detected by RT-PCR. In addition, the expression of arginase II and arginase I mRNA was attenuated by 30 minutes and one hour of reperfusion, and returned to baseline values after 24 hours of reperfusion. CONCLUSIONS: Ischemic ARF is associated with augmented tubular CAT-2 mRNA expression, which leads to enhanced l-Arg transport and increased NO production. This may contribute to the renal injury exhibited in iARF.     

Propofol reduces nitric oxide-induced apoptosis in testicular ischemia-reperfusion injury by downregulating the expression of inducible nitric oxide synthase

Background: The aim of the present study was to investigate the underlying mechanisms in the preventive effects of intravenous anesthetics on testicular ischemia–reperfusion injury.
Methods: Forty male Wistar Albino rats were randomly assigned to four groups of 10 rats each. Anesthesia was induced and maintained with thiopental in groups 1 and 2 and with propofol in groups 3 and 4. Groups 2 and 4 received left testicular ischemia (torsion) for 1 h and reperfusion (detorsion) for 24 h. Groups 1 and 3 (control groups) had no testicular torsion and detorsion. At 24 h of reperfusion, animals were killed and ipsilateral testes were removed for determination of tissue nitric oxide (NO) levels and immunohistochemical evaluation of endothelial nitric oxide synthase (eNOS), inducible NOS (iNOS), and apoptosis protease-activating factor 1 (APAF-1).
Results: Between groups 1 and 3, there were no differences in tissue NO levels and eNOS, iNOS, and APAF-1 expressions. iNOS and APAF-1 expressions were markedly increased in group 2, but these parameters were at the mild to moderate level in group 4 at 24 h of reperfusion. Also, elevated expression of iNOS was accompanied by a high NO production in group 2 compared with group 4. Although eNOS expressions were increased in both the groups (groups 2 and 4), there were no significant differences between these groups.
Conclusions: Propofol as an anesthetic agent may attenuate germ cell-specific apoptosis and decrease NO biosynthases through downregulation of iNOS expression in an animal model of testicular torsion and detorsion.     

Acupuncture stimulation of ST-36 (Zusanli) significantly mitigates acute lung injury in lipopolysaccharide-stimulated rats

BACKGROUND: We sought to investigate the potential therapeutic effects of acupuncture stimulation of ST-36 (Zusanli) on endotoxemia-induced acute lung injury in lipopolysaccharide (LPS)-stimulated rats. METHODS: Sixty rats were randomized into six groups (n = 10): (i) lipopolysaccharide (LPS) control group, (ii) normal saline (N/S) control group, (iii) LPS plus ST-36 group, (iv) N/S plus ST-36 group, (v) LPS plus sham point (Sham) group, and (vi) N/S plus Sham group. Manual acupuncture stimulation of ST-36 (designated as 'ST-36') or a 'non-acupoint' (designated as 'Sham') was performed in lightly immobilized rats for 30 min. Then, LPS injection was employed to induce sepsis. Rats were killed at 6 h after LPS injection and lung injury, nitric oxide (NO) biosynthesis and inducible NO synthase (iNOS) expression were assayed. RESULTS: Significant lung injury, pulmonary iNOS expression and systemic and pulmonary NO biosynthesis were noted in the LPS groups. Rats in the LPS plus Sham group had lung injury, pulmonary iNOS expression, systemic and pulmonary NO biosynthesis similar to those observed in the LPS group. However, the degree of lung injury, pulmonary iNOS expression and pulmonary NO biosynthesis, but not systemic NO biosynthesis, were significantly attenuated in the LPS plus ST-36 group as compared with those in both the LPS group and the LPS plus Sham group. CONCLUSION: Acupuncture stimulation of ST-36 may be effective as a prophylaxis measure against sepsis. However, results from this study do not support the use of acupuncture for the treatment of sepsis.     

L-arginine deficiency and supplementation in experimental acute renal failure and in human kidney transplantation

BACKGROUND: The "L-arginine paradox" refers to situations where L-arginine (L-Arg) supplementation stimulates nitric oxide (NO) synthesis, despite saturating intracellular concentrations. This paradox is frequently observed in acute renal failure (ARF). First, the effects of L-Arg on renal function of rats with ARF were studied. Based on the promising results from these initial studies, the second part of our study searched for a form of ARF in humans that could be studied easily under conditions with little variance and yet was linked with endothelial dysfunction. Thus, we investigated the effects of L-Arg supplementation immediately after kidney transplantation in 54 patients. METHODS: In uranyl nitrate-induced ARF in rats the effects of L-Arg and L-NNA (inhibitor of nitric oxide synthase; NOS) on glomerular filtration rate (GFR), renal plasma flow (RPF), blood pressure (BP) and NOx (NO2- +NO3-) excretion were examined. Tissue L-Arg levels, NOS activities, immunodetection of NOS and superoxide dismutase (SOD), activities of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and xanthine oxidase, and nitrotyrosine immunoreactive protein (NT-IR) were determined and compared to sham operated animals. Secondly, in a randomized, double-blind study, the effects of L-Arg on GFR and RPF were investigated in 54 kidney transplant recipients, receiving IV L-Arg for three days. GFR and RPF were measured on days 1, 3, 5 and 10 by scintigraphy. RESULTS: In experimental ARF, decreased RPF and GFR were associated with reduced tissue L-Arg levels, endothelial NOS-III expression, NO formation and NOx excretion. Reduction in GFR, RPF and NOx excretion were reversed upon administration of exogenous L-Arg. There also was a loss of Cu,Zn-SOD, a key enzyme against oxidative stress, and an elevation of NT-IR, an indicator of nitrosative stress and suggested marker for pathological actions of NO. However, NT-IR was not dependent on de novo NO synthesis and not related to the functional effects of l-Arg administration. In kidney transplant recipients receiving organs with a short cold ischemia time (CIT) and from young donors, that is, those with a higher likelihood of a functional endothelium, early administration of L-Arg improved renal function. CONCLUSION: Both experimental and clinical data show that \L-Arg deficiency and endothelial dysfunction are pathomechanistically relevant in ARF. The data suggest a therapeutic potential for the administration of L-Arg in ARF and kidney transplantation, at least in patients receiving kidneys with shorter CIT and from younger donors.     

Differential regulation of L-arginine transporters (cationic amino acid transporter-1 and -2) by peroxynitrite in rat mesangial cells.

BACKGROUND: It has become evident that increased nitric oxide (NO) generation may be associated with production of reactive oxygen species, such as peroxynitrite (ONOO-). Peroxynitrite has been postulated to be responsible for several of the cytotoxic effects previously ascribed to NO. Since cellular arginine uptake has been shown to modulate nitric oxide synthase activity, we were intrigued to study the effect of ONOO- on arginine traffic in renal mesangial cells. METHODS: Arginine uptake, CAT-1 and CAT-2 mRNA expression by northern blotting analysis, and CAT-1 protein content using western blotting were determined in mesangial cells pre-treated with peroxynitrite (0.1 and 0.5 mM) for 2 h. RESULTS: Peroxynitrite induced a significant increase in arginine uptake and CAT-2 mRNA expression compared with untreated cells. In contrast, CAT-1 mRNA expression and protein abundance were diminished. CONCLUSIONS: In rat mesangial cells, peroxynitrite augments arginine uptake via augmentation of CAT-2 while decreasing CAT-1 expression.     

L-Arginine supplementation increases mesangial cell injury and subsequent tissue fibrosis in experimental glomerulonephritis.

BACKGROUND: Mesangial cell lysis in the antithymocyte serum (ATS)-induced model of glomerulonephritis is dependent on the generation of cytotoxic nitric oxide (NO) through transient induction of NO synthase (iNOS). We hypothesized that increased availability of L-arginine (L-Arg) during mesangial cell lysis might provide iNOS with increased substrate leading to increased lysis, and that this increased lysis would be reflected in more severe fibrotic disease at day 6. METHODS: To ensure whole body equilibration with high L-Arg at the time of injury, rats were pretreated with 1% L-Arg in drinking water for one week prior to the administration of ATS. Animals were sacrificed six hours after ATS injection when previous experiments had indicated iNOS induction had occurred and at six days. At six hours, plasma was obtained for L-Arg levels and nitrite/nitrate (NOx) content. Renal tissues were taken for histological evaluation of glomerular cell counts, macrophage infiltration (ED-1), and iNOS expression. Glomeruli were isolated for detection of iNOS mRNA and placed in culture to study the dependence of NO production on L-Arg concentration. In rats sacrificed at six days, L-Arg supplementation was stopped 16 hours after ATS injection. Fibrotic disease was evaluated by urinary protein excretion, histological assessment of glomerular cell number, matrix accumulation, and production of transforming growth factor-beta1 and matrix components fibronectin and plasminogen activator inhibitor type-1 (PAI-1) by isolated glomeruli in culture. RESULTS: At six hours, the glomerular cell number was significantly reduced by ATS injection (P < 0.01) and further significantly (P < 0. 05) reduced by L-Arg feeding [normal control (NC) = 64.2 +/- 1, ATS = 53.4 +/- 0.7, ATS + L-Arg = 50.8 +/- 0.7]. Disease increased macrophage infiltration and iNOS protein and iNOS mRNA levels markedly (P < 0.01), whereas L-Arg feeding did not further increase these variables. Plasma L-Arg levels (nmol/ml) were reduced by disease (NC = 121 +/- 9, ATS = 84 +/- 13, P < 0.01) and elevated by L-Arg feeding (ATS + L-Arg = 166 +/- 12, P < 0.01). Plasma NOx was significantly increased by ATS and further increased by ATS + L-Arg (P < 0.05). Production of NOx by cultured glomeruli showed striking L-Arg concentration dependence in six hours but not in normal glomeruli. In the group sacrificed at day 6, day 2 proteinuria was higher in the ATS + L-Arg group compared with the ATS alone group (P < 0.05). Measures of fibrotic disease at day 6 all showed large increases over control with ATS alone (P < 0.01), and further small, but significant increases when L-Arg was combined with ATS (P < 0.05). CONCLUSIONS: The results indicate that if given during disease induction, L-Arg supplementation can enhance iNOS-dependent tissue injury by providing increased substrate. Although the increase in injury with L-Arg supplementation was small, it led to increased fibrosis at day 6. These data predict that in diseases with repeated iNOS-dependent tissue injury, L-Arg supplementation may produce cumulative increases in tissue fibrosis.     

Nitric oxide, sepsis, and the kidney

Although excess nitric oxide (NO) production plays a major role in the hypotension characteristic of sepsis, concurrent constitutive NO generation in the kidney during sepsis is essential for preservation of renal perfusion and prevention of glomerular thrombosis. The authors have shown that although all nitric oxide synthase (NOS) inhibitors restore normal blood pressure in lipopolysaccharide (LPS) treated rats, only selective inducible NOS (iNOS) inhibition prevents the reductions in glomerular filtration rate (GFR), whereas nonselective inhibition of NOS further decreases GFR. Glomerular endothelial NOS (eNOS) activity was found to be inhibited by LPS. The decrease in eNOS activity was completely prevented by selective iNOS inhibition in vivo and in vitro. The adverse renal outcomes after LPS administration correlated with decreased glomerular eNOS activity rather than elevated NO production. These findings suggest that the decrease in GFR after LPS is caused by local inhibition of eNOS by iNOS possibly via NO autoinhibition. Selective inhibition of iNOS could represent a substantially superior approach for the treatment of the sepsis syndrome.     

Liposome-mediated transfer of nitric oxide synthase gene improves renal function in ureteral obstruction in rats

BACKGROUND: The protective effect of nitric oxide has been demonstrated in several renal disease models. We augmented renal nitric oxide production by transfer of the inducible nitric oxide synthase (iNOS) gene into rat kidney in controls and in unilateral ureteral obstruction (UUO). METHODS: The human iNOS gene was inserted into a pcDNA 3.1-backbone plasmid with the FLAG epitope (FLAG-iNOS). In vitro, transduction of FLAG-iNOS was confirmed by Western blot and Griess reaction. In vivo, we transfected either FLAG-iNOS or control plasmid (CMV-LacZ), using cationic liposomes. Urinary nitric oxide metabolites and immunohistochemistry confirmed iNOS transduction. Renal function was also assessed. RESULTS: In vitro, increased iNOS expression was demonstrated in human embryonic kidney (HEK293) cells, along with increased release of nitric oxide metabolites, NO(2)/NO(3). In vivo, FLAG-iNOS was detected by polymerase chain reaction (PCR) up to 35 days after the transfection. Urine collection documented increased urinary NO(2)/NO(3). Immunohistochemistry localized iNOS to collecting ducts, distal tubules, and glomerulus of the injected kidney. Renal function measured up to 21 days after transfection in control animals was not significantly different between the two groups. In contrast, renal function after 24 hours of UUO was significantly improved in FLAG-iNOS-treated animals. CONCLUSION: This study demonstrates the feasibility of liposome-mediated iNOS gene transfer into the kidney. Furthermore, the improvement of renal function in UUO demonstrates that the transfected iNOS gene is active and suggests that decreased iNOS activity contributes to the decreased renal function in UUO. This iNOS construct may have therapeutic utility in the pathophysiologic sequelae of UUO and other renal diseases.     

Expression of two isozymes of acyl-coenzyme A: Cholesterol acyltransferase-1 and -2 in clear cell type renal cell carcinoma

Objectives:   The present study investigated the expression of acyl-coenzyme A: cholesterol acyltransferase-1 (ACAT-1) and -2 in clear cell type renal cell carcinoma (RCC).
Methods:   Clear cell type RCC and corresponding normal kidney tissue samples were obtained from 19 surgical cases (28–85 years of age). Tissue extracts were assayed for ACAT activity and protein expression by immunoblotting with anti-ACAT-1 and anti-ACAT-2 antibodies. Frozen sections were subjected to Oil red O staining for lipids, and were immunostained with ACAT-specific antibodies.
Results:   Acyl-coenzyme A cholesterol acyltransferase activity was 5.7-fold higher ( P  < 0.01) in clear cell carcinoma (23.52 ± 4.90 pmol/mg protein/min) than in normal kidney (4.12 ± 0.36). Consistent with this, immunoblotting and immunohistochemical staining revealed strong expression of ACAT-1 in clear cell type RCC. Densitometric analysis showed that ACAT-1 expression was 2.9-fold higher in clear cell type RCC than in normal kidney. In contrast, ACAT-2 expression was negative in clear cell type RCC and normal kidney. Oil red O staining showed massive deposits of lipid in RCC cells.
Conclusions:   We identified strong expression of ACAT-1 in clear cell type RCC. Upregulation of ACAT-1 leads to high ACAT enzymatic activity, which accelerates the accumulation of cholesterol ester in clear cell type RCC.     

The effects of arginine and selective inducible nitric oxide synthase inhibitor on pathophysiology of sepsis in a CLP model

BACKGROUND: Sepsis is an arginine-deficient state and is associated with overproduction of nitric oxide (NO) by inducible nitric oxide synthase (iNOS). It has been indicated that low plasma levels of arginine are related to high mortality rates in sepsis. Arginine, however, is also known to be a precursor of NO. Therefore, administration of arginine in septic patients remains controversial. We examined the effects of co-administration of arginine and aminoguanidine, a selective iNOS inhibitor, on sepsis, using rat models. METHOD: Sepsis was induced in rats by cecal ligation and puncture (CLP). Effects of separate and combined administration of arginine and aminoguanidine were investigated by comparing plasma levels of arginine, expressions of heme oxygenase (HO)-1 and HO-2 in liver and lung, and nitrite + nitrate (NOx) excretion in urine, as well as neuroendocrine responses in urine in the early phase of sepsis. Seven-day survival rates were also examined. RESULTS: A combination of arginine and aminoguanidine recovered the plasma level of arginine at 6 h post-CLP, decreased expression of HO-1 in liver and lung at 24 h post-CLP, decreased urinary excretion of epinephrine, norepinephrine, dopamine, and 17-hydroxycorticosteroid in the first 24 h post-CLP, and increased 7-d survival. CONCLUSION: It is demonstrated that administration of arginine together with the selective iNOS inhibitor in the early phase of sepsis restores plasma arginine, reduces oxidative stress by probably maintaining NO derived from constitutive NOS, and attenuates neuroendocrine stress responses. This co-administration may be a beneficial treatment approach against sepsis.     

阻塞性黄疸时L-精氨酸对肾功能的保护作用

目的：研究阻塞性黄疸（OJ）时，L－精氨酸（L－Arg)对肾功能的保护作用。方法：胆总管结扎大鼠30只，随机分成生理盐水对照（NS）组、L－精氨酸（L－Arg)组和L－硝基精氨酸（L－NNA）组，每组10只。胆总管结扎后第2天起分别腹腔注射1ml NS、1ml L-Arg(500mg/kg)、1ml L-NNA(10mg/kg)，连用9d；假手术（SO）组用1ml NS腹腔注射。观察各组肾功能的变化，同时测定血和肾组织内皮素（ET）、一氧化氮（NO）水平、一氧化氮合酶（NOS）活性和丙二醛（MDA）的含量。并用图像分析检测ET1 mRNA和NOS mRNA表达的部位及量的变化。结果：用L－Arg后，血和肾组织NOS活性增加，肾组织ET1 mRNA表达减少，血和肾组织ET下降，NO升高；同时伴有内生肌酐清除率（Ccr)、肾皮质平均血流（RCBF）的升高，肾组织MDA含量降低。结论：L－Arg通过增强血和肾组织NOS活性来增加体内NO水平、抑制ET1 mRNA表达、降低体内ET水平，从而提高Ccr与RCBF，减轻阻塞性黄疸时的肾功能损伤。