Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.6.1.2 (alanine aminotransferase)
 26,722 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The role of nitric oxide (NO) and peroxynitrite in the process of neutrophil adhesion and infiltration was investigated in a model of hepatic ischemia-reperfusion. Male Fischer rats were subjected to 30 min of hepatic no-flow ischemia followed by 4 h of reperfusion (I/R). I/R induced liver injury as evidenced by a 13.7-fold increase in plasma alanine aminotransferase activity. Induction of liver injury was associated with an increase in neutrophil accumulation in ischemic lobes of livers [215 +/- 27 polymorphonuclear neutrophil leukocytes/50 high-power field (HPF), P < .05 compared with sham control] and 8-fold augmentation of inducible NO synthase (NOS) activity. However, NO levels in the liver decreased; this decrease may be caused by peroxynitrite formation by the reaction of NO with superoxide. Sections of ischemic lobes of the liver tissue of I/R animals exhibited marked immunoreactivity with anti-nitrotyrosine antibody, which indicates the presence of nitrotyrosine. Administration of Nw-nitro-L-arginine methyl ester (10 mg/kg i.v. before reperfusion) attenuated total and inducible NOS activity in both ischemic and nonischemic lobes of liver, and reduced NO levels in plasma and liver. However, NOS inhibition aggravated liver injury as alanine aminotransferase increased by 61% compared with rats subjected to reperfusion injury. Neutrophil accumulation was enhanced in ischemic (436 +/- 48/50 HPF, P < .05 compared with I/R animal) and nonischemic lobes of livers (34 +/- 3.2/50 HPF, P < .05 compared with sham control). NOS inhibition also attenuated immunohistochemically detected nitrotyrosine formation, but increased superoxide production in the liver. The NO-dependent regulation of neutrophil accumulation in the liver may be linked closely to P-selectin and intracellular adhesion molecule-1 expression because inhibition of NOS resulted in significant increases in gene expression of these two adhesion molecules (determined by reverse transcription-polymerase chain reaction analysis). These results suggest that NO is important in attenuating neutrophil accumulation and liver damage in ischemia-reperfusion injury. Inhibition of NOS activity reduces peroxynitrite formation but aggravates liver injury and increases neutrophil accumulation, which suggests that the anti-inflammatory function of NO is more important than the cytotoxic potential of peroxynitrite in acute inflammation.
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PMID:Inhibition of nitric oxide synthase attenuates peroxynitrite generation, but augments neutrophil accumulation in hepatic ischemia-reperfusion in rats. 949 76

The role of nitric oxide (NO) on liver oxidative stress and tissue injury in rats subjected to tourniquet shock was investigated. This shock model differs from others in that injury is a consequence of remote organ damage. Liver oxidative stress becomes evident after hind limb reperfusion, as evidenced by the loss of total tissue thiols; by increases in tissue oxidized glutathione (GSSG), lipid peroxidation (LPO), plasma aminotransferases (alanine aminotransferase (ALT) and (aspartate aminotransferase (AST)), and plasma nitrites; and by a 36% loss in total superoxide dismutase (SOD) activity. Portal blood flow is reduced by 54.1% after 2 h of hind limb reperfusion. Inhibition of NO synthesis with Nomega-nitro-L-arginine methyl ester or L-arginine methyl ester increased mean arterial blood pressure; further reduced portal blood flow; and aggravated liver injury as assessed by further loss in total thiols, increased LPO and GSSG content, and further increases in plasma ALT and AST. Total plasma nitrites were lower than in control animals, and total tissue SOD activity decreased by more than 80%. Treatment with the NO donor sodium nitroprusside reverted the decrease in portal blood flow and also reverted tissue thiol loss, LPO, and GSSG increases, as well as the loss of ALT and AST to plasma and of SOD activity to levels comparable to untreated control shock animals. As expected, plasma nitrites were greater than in tourniquet control animals. These data support the hypothesis that endogenous NO formation protects the rat liver from the consequences of oxidative stress elicited by hind limb reperfusion in rats subjected to tourniquet shock.
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PMID:Inhibition of nitric oxide synthesis aggravates hepatic oxidative stress and enhances superoxide dismutase inactivation in rats subjected to tourniquet shock. 961 80

Treatment of mice with a toxic dose of acetaminophen (300 mg/kg, ip) significantly increased hepatotoxicity at 4 h, as evidenced by histological necrosis in the centrilobular areas of the liver, and increased serum levels of alanine aminotransferase (ALT) (from 8 +/- 1 IU/L in saline-treated mice to 3226 +/- 892 IU/L in the acetaminophen-treated mice). Serum levels of nitrate plus nitrite (a marker of nitric oxide synthesis) were also increased from 62 +/- 8 microM in saline-treated mice to 110 +/- 14 microM in acetaminophen-treated mice (P < 0.05). Regression analysis of serum ALT levels to serum nitrate plus nitrite levels in individual mice revealed a positive, linear relationship between serum ALT levels and serum nitrate plus nitrite levels with a correlation coefficient of 0.9 (P < 0.05). The y intercept value (nitrate plus nitrite level) was 63 +/- 15 microM. Immunohistochemical analysis of liver sections from acetaminophen-intoxicated mice using an anti-3-nitrotyrosine antibody indicated tyrosine nitration in the proteins of the centrilobular cells. Tyrosine nitration has been shown to occur by peroxynitrite, a reactive intermediate formed by an extremely rapid reaction of nitric oxide and superoxide and a species which also has hydroxyl radical-like activity. Analysis of liver sections using an anti-acetaminophen antiserum indicated the centrilobular cells also contained acetaminophen-protein adducts, a reaction of the metabolite N-acetyl-p-benzoquinone imine with cysteine residues on proteins. These data are consistent with acetaminophen metabolic activation leading to increased synthesis of nitric oxide and superoxide and to peroxynitrite as an important intermediate in the toxicity.
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PMID:Nitrotyrosine-protein adducts in hepatic centrilobular areas following toxic doses of acetaminophen in mice. 962 27

The nuclear enzyme poly(ADP-ribose) synthetase (PARS) is activated by DNA strand breakage, caused, for example by nitric oxide (NO), peroxynitrite, or oxygen-derived free radicals. Activation of PARS can cause intracellular energy depletion and cell death in vitro and may play a role in the circulatory and organ failure caused by endotoxin (LPS). Here we investigate the effects of various chemically distinct inhibitors of PARS activity (3-aminobenzamide, nicotinamide, 1,5-dihydroxyisoquinoline) on circulatory failure and organ dysfunction caused by LPS in the rat. Administration of endotoxin caused circulatory failure, acute renal dysfunction, hepatocellular injury and dysfunction, pancreatic injury, elevation of plasma lactate levels, and overproduction of NO. None of the PARS inhibitors used reduced the circulatory failure, the renal dysfunction, rise in lactate, or the overproduction of NO caused by LPS. Although 1,5-dihydroxyisoquinoline (ISO) attenuated the rises in the serum levels of bilirubin, alanine aminotransferase (ALT) (indicators of liver injury/dysfunction), and lipase (indicator of pancreatic injury); a similar effect was also observed with the vehicle for ISO, dimethyl sulfoxide (DMSO), which is a well known scavenger of hydroxyl radicals. Thus, the beneficial effects of ISO are unlikely to be due to inhibition of PARS activity, but may be due to the scavenging of free radicals by its vehicle DMSO. Activation of PARS does not contribute to the circulatory failure, renal dysfunction, lactic acidosis, or the overproduction of NO and is unlikely to contribute to the liver injury/dysfunction caused by endotoxic shock in the rat.
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PMID:Effects of inhibitors of poly(ADP-ribose) synthetase activity on hypotension and multiple organ dysfunction caused by endotoxin. 968 85

The vasodilator nitric oxide (NO) is involved in the regulation of systemic blood pressure and local organ blood flow. Inhibitors of the constitutively expressed nitric oxide synthase in endothelial cells (eNOS), e.g., Nomega-nitro-L-arginine methyl ester hydrochloride (L-NAME), aggravated liver injury in a variety of models. On the other hand, inhibitors of the inducible NOS (iNOS), e.g., 2-aminoethyl-isothiourea (AET), were found to be beneficial during endotoxemia. The aim of this investigation was to study the effect of AET compared with L-NAME on liver microvascular blood flow and injury in more complex models with multiple insults, i.e., ischemia (20 min)-reperfusion (8 h) in combination with .5 mg/kg endotoxin (IRE). Male Fisher rats were treated with 10 mg/kg AET or L-NAME and subjected to IRE. At 8 h, liver injury (plasma ALT: 1320+/-164 U/L) was significantly increased in AET-treated (5,018+/-1,379 U/L) and L-NAME-treated groups (2,429+/-228 U/L). Each inhibitor attenuated microvascular blood flow (assessed by laser Doppler flowmetry) to a similar degree. In striking contrast, AET completely reversed the endotoxin-induced impairment of the microvascular blood flow and significantly protected against an endotoxin-induced liver injury (plasma ALT: 3,007+/-268 U/L (ET); 460+/-39 U/L (ET+AET)). Infusion of endothelin-1 reduced microvascular blood flow by 50-60% and caused liver injury. Our data demonstrated that an inhibitor of eNOS (L-NAME) has a consistent detrimental effect on liver injury during ischemia-reperfusion and endotoxemia mainly because it can cause additional ischemia by reducing the microvascular blood flow. However, selective inhibitors of iNOS (AET) can impair hepatic blood flow and aggravate the injury or improve blood flow and attenuate organ injury depending on the experimental model. These results suggest that iNOS inhibitors may not be universally beneficial and should be tested in a variety of experimental models of sepsis/endotoxemia before used in clinical settings.
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PMID:Differential effect of 2-aminoethyl-isothiourea, an inhibitor of the inducible nitric oxide synthase, on microvascular blood flow and organ injury in models of hepatic ischemia-reperfusion and endotoxemia. 968 86

Overproduction of tumor necrosis factor (TNF-), interleukin-1beta (IL-1beta), and nitric oxide (NO) is believed to be detrimental during the progression of acute pancreatitis, yet little is known about the hepatic production of these mediators and their role in mediating pancreatitis-induced hepatic dysfunction. Rats were randomized to receive a single intraperitoneal injection of the macrophage-pacifying compound, CNI-1493 (1.0 mg/kg), or vehicle 1 hour before the induction of retrograde bile salt pancreatitis. Sham-operated animals served as controls. Animals were killed 18 hours later, with serum and livers harvested to determine the degree of hepatocellular injury and the induction of TNF-, IL-1beta, and inducible nitric oxide synthase (iNOS). In addition, serum TNF- and nitrites (end-product of NO breakdown) were determined in each group to assess the mechanism of action of CNI-1493. TNF-, IL-1beta, and iNOS gene expression (by reverse-transcription polymerase chain reaction) as well as aspartate transaminase (AST), alanine transaminase (ALT), and lactic dehydrogenase (LDH) (but not alkaline phosphatase [ALP]) increased following the development of pancreatitis (all P < .05). Macrophage pacification significantly prevented the induction of TNF- and IL-1beta mRNA (but not iNOS), resulting in lessened serum AST, ALT, and LDH (all P < .05). Serum TNF- protein and nitrites correlated with gene induction in that both were increased following the onset of pancreatitis, and TNF- protein production was significantly attenuated in animals receiving CNI-1493. Hepatocellular, but not bile duct, injury occurs during experimental pancreatitis that is associated with hepatic TNF-, IL-1beta, and iNOS mRNA gene induction, as well as TNF- protein and nitrite production. Preventing the production of TNF- and IL-1beta by macrophage pacification attenuates the hepatocellular damage, suggesting that these mediators play a role in pancreatitis-induced hepatic injury.
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PMID:Macrophage pacification reduces rodent pancreatitis-induced hepatocellular injury through down-regulation of hepatic tumor necrosis factor alpha and interleukin-1beta. 979 13

In the present work, the relation of cytoprotection of neurotensin to nitric oxide (NO), cGMP and cAMP was investigated in primary cultured mouse hepatocytes. The results are as follows: After administration of acetaminophen (20 mmol/L) to the medium, the leakage of GOT and GPT increased significantly. Pretreatment with neurotensin (10(-7) mol/L) before acetaminophen reduced the leakage of GOT and GPT. No synthase inhibitor, L-NAME, completely blocked the cytoprotective effect of neurotensin. Neurotensin could enhance the intracellular cGMP content, but had no effect on cAMP content. These results indicate that the protective effect of neurotensin on hepatocytes is mediated by NO probably by enhancing intracellular cGMP content.
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PMID:[Involvement of nitric oxide and cGMP in the protective effect of neurotensin on hepatocytes]. 981 81

The anti-inflammatory role of nitric oxide (NO) was studied in a model of hepatic ischemia-reperfusion (I/R) in rats. Male Fischer rats were subjected to 30 min of no-flow ischemia of the left and median lobes of the liver, and animals were examined for a 4-h period of reperfusion. The animals were divided into the following groups: control-vehicle; I/R-vehicle; I/R-Nomega-nitro-L-arginine methyl ester (L-NAME, 10 mg/kg iv, 10 min before reperfusion); sham control-L-NAME, and I/R-S-nitroso-N-acetyl-penicillamine (SNAP, 25 micromol/kg iv, 10 min before reperfusion, followed by 20 micromol. kg-1. h-1 in 1.0 ml saline infused for 4 h). Results showed that mean arterial blood pressure was significantly increased in the sham control-L-NAME or I/R-L-NAME groups compared with either the I/R-vehicle or I/R-SNAP groups. However, cardiac index (CI) and stroke volume index (SVI) were markedly decreased, and systemic vascular resistance index (SVRI) was dramatically increased. Interestingly, the CI and SVI in rats treated with SNAP were markedly improved over that of the I/R group. Plasma nitrate and nitrite levels were significantly decreased in the I/R-L-NAME group; however, superoxide generation in the ischemic lobes and plasma alanine aminotransferase activity were higher compared with I/R-SNAP rats. The L-NAME-induced enhancement of hepatic injury in rats with I/R may be due in part to neutrophil infiltration, which was significantly increased compared with animals subjected to I/R or I/R-SNAP. The mechanism of L-NAME-enhanced neutrophil infiltration may be due to the fact that the ratios of P-selectin and intercellular adhesion molecule 1 (ICAM-1) mRNA to glyceraldehyde-3-phosphate dehydrogenase mRNA extracted from the ischemic lobes of I/R-L-NAME rats were significantly increased when compared with the I/R-SNAP group. These results suggest that 1) endogenous NO reduces the SVRI and permits an increased CI and SVI; 2) exogenous NO further improves CI and SVI; and 3) endogenous, but not exogenous, NO decreases P-selectin and ICAM-1 mRNA expression, thereby reducing polymorphonuclear neutrophil-dependent reperfusion tissue injury.
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PMID:NO modulates P-selectin and ICAM-1 mRNA expression and hemodynamic alterations in hepatic I/R. 984 19

Nitric oxide, a free radical inter- and intracellular messenger molecule, is important in exercise physiology. This study tested the hypothesis that serum nitric oxide concentrations change after strenuous exercise with severe generalized muscle cramps. The study group consisted of 77 professional football players in preseason training. All players' concentrations of serum nitrite and of other serum chemicals were determined during their preseason evaluations and compared with the concentrations in 40 serum samples taken from 25 of those same players who required intravenous rehydration for severe generalized muscle cramps after a training session. Player weight and percentage of body fat were significantly higher in players who received intravenous fluids than in players who did not. The serum of players requiring intravenous hydration showed evidence of skeletal muscle breakdown (increases in lactate dehydrogenase, creatinine phosphokinase, aspartate aminotransferase, and alanine aminotransferase) and of dehydration (elevations in protein, blood urea nitrogen, and cholesterol). The major finding, however, was a nearly 300% increase in serum nitrite concentrations in players requiring rehydration. There were no correlations between concentrations of nitrate and of any of the other serum chemicals. These data support the hypothesis that large amounts of nitric oxide are synthesized in professional football players after strenuous exercise with severe muscle cramps. The study design did not allow us to determine whether this increase in nitric oxide was due to exercise or muscle cramps or both, but it does provide a basis for evaluating these relationships.
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PMID:Postexercise increase in nitric oxide in football players with muscle cramps. 1049 91

The aim of this study was to evaluate the protective or deleterious effects of endogenous nitric oxide (NO) on liver cells during hepatic ischemia-reperfusion (IR) in the rat. Injury to hepatocytes and endothelial cells was evaluated by determining cytolysis-marker activity in plasma (alanine transaminase [ALT]; aspartate transaminase [AST]) and plasma hyaluronic acid (HA) concentration. Clamping the hepatic pedicle for 45 minutes caused a significant increase in plasma AST and ALT activity after 30 minutes of reperfusion, which reached a maximum (+270% and +740%, respectively) after 6 hours of reperfusion. Plasma HA concentration was significantly higher (+130%) only after 6 hours of reperfusion. Administration of a nonselective NO synthase (NOS) inhibitor, Nomega-nitro-L-arginine (L-NNA; 10 mg/kg iv), 30 minutes before IR, caused marked aggravation of postischemic liver injury, as shown by plasma ALT and AST activity and HA concentration. This deleterious effect was partially prevented by the simultaneous injection of L-arginine, the endogenous NO precursor (100 mg/kg iv). Interestingly, L-arginine alone limited postischemic damage (AST, -25%; ALT, -45%; HA, -21% vs. untreated IR rats at 6 hours reperfusion). Pretreatment with the Guanosine 3':5'-cyclic monophosphate-independent vasodilator, prazosin, partially reversed L-NNA effects, but it did not protect untreated IR animals. Pretreatment with aminoguanidine, a selective inhibitor of inducible NOS, did not aggravate hepatic IR injury. Thus, endogenous NO, probably produced by an early and transient activation of a constitutive NOS, protects both hepatocytes and endothelial cells against liver ischemia-reperfusion injury, and this effect is not entirely a result of vasorelaxation.
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PMID:Hepatoprotective effect of endogenous nitric oxide during ischemia-reperfusion in the rat. 1005 83


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