Role of glutathione status in protection against ethanol-induced gastric lesions

The role of glutathione status in gastric mucosal cytoprotection has been a subject of controversy. Cysteamine, an exogenous sulfhydryl agent and diethyl maleate (DEM), an endogenous glutathione (GSH) depletor both appear to protect rats from ethanol-induced gastric lesions. In this study, we used various agents to alter gastric mucosal GSH levels and assessed the effects on susceptibility to ethanol injury. We found that DEM and buthionine sulfoximine both depleted gastric GSH but only DEM protected against ethanol-induced gastric lesions. L-Oxothiazolidine-4-carboxylate (OXT) and N-acetyl-L-cysteine (NAC) both potentiated ethanol-induced gastric lesions even though only NAC significantly raised the GSH level. The depletion of GSH by DEM was reversed by supplying cysteine in the form of OXT or NAC so that the net result was a GSH level close to normal control. The potentiation of ethanol injury by NAC and OXT was still apparent. These experiments show no relation between gastric GSH levels and susceptibility to ethanol injury.     

Role of nitric oxide and reduced glutathione in the protective effects of aminoguanidine, gadolinium chloride and oleanolic acid against acetaminophen-induced hepatic and renal damage

The potential protective role of aminoguanidine (AG), gadolinium chloride (GdCl(3)) and oleanolic acid (OA) in acetaminophen (APAP)-induced hepatotoxicity and nephrotoxicity was investigated in rats. Pretreatment of rats with AG (50mg/kg) orally, GdCl(3) (10mg/kg) intramuscularly or OA (25mg/kg) intramuscularly protected markedly against hepatotoxicity and nephrotoxicity induced by an acute oral toxic dose of APAP (2.5g/kg) as assessed by biochemical measurements and by histopathological examination. None of AG-, GdCl(3)- or OA-pretreated animals died by the acute toxic dose of APAP. Concomitantly, pretreatment of rats with these agents suppressed the profound elevation of nitric oxide (NO) production and obvious reduction of intracellular reduced glutathione (GSH) levels in liver and kidney induced by the acute toxic dose of APAP. Similarly, daily treatment of rats with a smaller dose of AG (10mg/kg), GdCl(3) (3mg/kg) or OA (5mg/kg) concurrently with a smaller toxic dose of APAP (750mg/kg) for 1 week protected against APAP-induced hepatotoxicity and nephrotoxicity. This treatment also completely prevented APAP-induced mortality and markedly inhibited APAP-induced NO overproduction as well as hepatic and renal intracellular GSH levels reduction. These results provide evidence that inhibition of NO overproduction and consequently maintenance of intracellular GSH levels may play a pivotal role in the protective effects of AG, GdCl(3) and OA against APAP-induced hepatic and renal damages.     

Role of nitric oxide in gastric injury induced by hemorrhagic shock in rats

The aim of this study was to investigate the effect of nitric oxide (NO) on the gastric injury induced by hemorrhagic shock. Hemorrhagic shock was created by withdrawing 3 ml blood/200 g body weight of the rats. Before the hemorrhage, N(G)-nitro-L-arginine methyl ester (L-NAME, 10 mg/kg i.v. bolus), D-NAME (10 mg/kg i.v. bolus), or L-arginine (100 mg/kg i.v. bolus and 10 mg/kg/min infusion) + L-NAME were administered. At the end of the 1-hour hypovolemic shock period, histological analysis, gastric ulcer index, gastric myeloperoxidase (MPO) activity, and gastric protein oxidation (PO) levels were determined. In histological analysis a destructive effect of L-NAME (NO synthase inhibitor) was demonstrated. L-NAME treatment increased gastric MPO activity, L-arginine reversed this effect and D-NAME had no effect. Tissue PO activity was found to be increased in L-NAME-treated rats; L-arginine treatment reversed this activity. It is concluded that gastric barrier function is altered after hemorrhagic shock, and L-arginine (NO precursor) can prevent mucosal injury in the stomach. This effect of NO may be on gastric blood flow and can be mediated by tissue neutrophils.     

Protective effect of silymarin against ethanol-induced gastritis in rats: Role of sulfhydryls,nitric oxide and gastric sensory afferents

Silymarin has been known to exert antioxidant, anti-carcinogenic and anti-inflammatory effects. In this study, we examined the effect of silymarin on gastritis in rats. Oral administration of silymarin dose-dependently decreased gastric lesions in ethanol-induced gastritis model. Silymarin also significantly suppressed the development of gastric lesions in aspirin- or water immersion-restraint stress-induced gastritis models. Further study demonstrated that the gastroprotective effect of silymarin was blocked by nitric oxide (NO) synthase inhibitor l-NAME, SH blocker N-ethylmaleimide or TRPV1 antagonist capsazepine in ethanol-induced gastritis model. In addition, ex vivo analysis revealed that ethanol-induced decrease in gastric mucus and non-protein sulfhydryl (NPSH) groups was significantly reversed by silymarin treatment and lipid peroxidation was also suppressed by silymarin in ethanol-induced gastritis model. Taken together, these results suggest that silymarin exerts gastroprotective effects and the gastroprotective effects of silymarin might be related to the protection of gastric mucosal NO and NP-SH and the modulation of capsaicin-sensitive gastric sensory afferents.     

Role of nitric oxide and mucus in ischemia/reperfusion-induced gastric mucosal injury in rats

The present study aims at investigating the role of nitric oxide (NO) on the oxidative damage in gastric mucosa of rats which received ischemia/reperfusion (I/R) and its relation to mucus. NO synthesis modulators such as L-arginine and N(G)-nitro-L-arginine methyl ester (L-NAME) were injected intraperitoneally to the rats 30 min prior to I/R which was induced by clamping the celiac artery and the superior mesenteric artery for 30 min and reperfusion for 1 h. As a result, I/R increased lipid peroxide production and decreased the contents of glutathione (GSH), cGMP and mucus as well as GSH peroxidase activities of gastric mucosa. I/R decreased the activity and protein of NO synthase (NOS) in gastric mucosa. Pretreatment of L-arginine, a substrate for NOS, prevented I/R-induced alterations of gastric mucosa. However, L-NAME, an NOS inhibitor, deteriorated oxidative damage induced by I/R. In conclusion, NO has an antioxidant defensive role on gastric mucosa by maintaining mucus, GSH and GSH peroxidase, which were related to preservation of cGMP and NOS in gastric mucosa.     

Role of gastric glutathione in smoke flavouring-induced gastric injury in rats

Some commercial liquid smoke flavourings have been shown to induce acute gastric mucosal injury in rats when given orally as a large single dose. The present study was carried out to examine the mechanism of action in rats of two selected smoke flavourings containing about 10% total acids as acetic acid. These flavourings and 10% acetic acid decreased the concentration of glutathione (GSH) in the glandular stomach. The decrease in gastric GSH was coupled with smoke flavouring-induced gastric injury. Pretreatment with N-ethylmaleimide, a GSH depletor, enhanced acetic acid-induced gastric injury. Pretreatment with cysteine, a sulphhydryl compound, protected rats against smoke flavouring-induced gastric injury. Aqueous fractions of the smoke flavourings, after removal of non-polar compounds and acidic organic compounds (including acetic acid) by diethyl ether extraction, decreased the gastric GSH concentration considerably and had a marked reactivity in vitro with GSH, but these fractions by themselves showed no ability to induce gastric injury. Addition of 10% acetic acid to these aqueous fractions caused greater gastric injury than 10% acetic acid alone, which suggests that these aqueous fractions contain the (unidentified) compound(s) that facilitate acetic acid-induced gastric injury. These findings indicate that gastric endogenous and exogenous sulphhydryls play an important part in gastric cytoprotection.     

Effect of black tea on lipid peroxide and glutathione levels in female rats

The effects of black tea (Camellia sinensis L.) on lipid peroxidation and glutathione (GSH) levels in carbon tetrachloride (CCl4)-treated female Wistar rats were examined. Two control groups and one treatment group were tested. The control groups were fed with a standard diet, while the black tea group was fed the standard diet plus 6% by weight dried black tea leaves. At the end of 2 months, a single dose of CCl4 (1 ml/kg, i.p.) in olive oil was administered to rats in one of the control groups and the black tea group. They were sacrificed after 2 hours. Rats in the other control group were administered olive oil in a similar fashion. Measurements were made of lipid peroxide levels in liver and plasma, glutathione levels in liver, and alanine transaminase (ALT) and aspartate transaminase (AST) activities in plasma. Liver lipid peroxide levels, plasma ALT and AST activities were significantly decreased in the black tea group compared with the CCl4-treated control group, while plasma lipid peroxide levels were not. These results are parallel to those previously found with Wistar male rats. Glutathione levels, however, were not significantly affected, in contrast to the data relating to male rats, either after CCl4 or black tea treatments. The results of our study add to the findings that black tea attenuates CCl4-induced hepatic injury but also indicates the susceptibility of glutathione levels to endocrinological effects.     

Role of nitric oxide produced by constitutive and inducible nitric oxide synthases in the mouse gastric fundus

In the present study, the role of nitric oxide (NO) produced by constitutive and inducible nitric oxide synthases (cNOS and iNOS, resepctively) on the contraction and relaxation of fundus in normal and lipopolysaccharide (LPS)-treated mice was examined. A whole fundic ring isolated from mice pretreated with reserpine was mounted in an organ bath containing Krebs' solution with 0.001 mmol/L atropine. Rings were contracted initially by 5-hydroxytryptamine (5-HT; 0.03 mmol/L) before relaxation was induced using ATP (0.03 mmol/L), ADP (0.03 mmol/L), pentoxifylline (0.002 mmol/L), electrical field stimulation (EFS; 50 V, 1 msec, 50 Hz, 3 min) and L-arginine (0.05 mmol/L). All drugs and EFS induced significant relaxation of isolated rings. The relaxations induced were significantly inhibited by N(G)-nitro-L-arginine methyl ester (L-NAME; 1.0 mmol/L). However, the iNOS inhibitors L-N(6)-(1-iminoethyl) lysine hydrochloride (L-NIL; 1.0 mmol/L) and amino guanidine (AMG; 1.0 mmol/L) had no significant effect on tissue relaxation. Then, the relaxant effects of 0.03 mmol/L ATP were tested on precontracted isolated fundic rings taken from 10 mg/kg LPS-treated animals. The non-selective NOS inhibitor L-NAME (10 mg/kg), the iNOS inhibitors L-NIL (3 mg/kg) and AMG (20 mg/kg) and betamethasone (0.1 mg/kg) were used to examine the role of NO produced by iNOS in the relaxation responses. It was found that the level of contraction induced by 0.03 mmol/L 5-HT in rings isolated from LPS-treated animals was significantly (P < 0.5) less than that in rings from untreated mice. However, precontracted tissues from LPS-treated mice were significantly relaxed by ATP and the relaxation response to ATP was significantly inhibited by L-NIL, ANG and betamethasone, but not by L-NAME. We suggest that, in LPS-treated mice, the production of NO from iNOS produces a reduction in the contractile response, as well as a decrease in NO formation by cNOS, resulting in changes to smooth muscle cell function.     

Role of glutathione in stabilization of nitric oxide during hypertension developed by inhibition of nitric oxide synthase in the rat

The present study examined the role of glutathione in the development of hypertension induced by long-term inhibition of nitric oxide (NO)-synthase. Three groups of rats were investigated: control group, L-NAME group: group with NO-synthase inhibition by N(G)-nitro-L-arginine methyl ester (L-NAME, 40 mg/kg per day) for 2 weeks, and BSO group: group with glutathione synthesis inhibitor L-buthionine sulfoximine (BSO, 1.4 mmol/kg per 12 h) for 3 days. All the groups were subjected to an acute i.v. experiment in which the given substances were exchanged between groups. There was no change in systolic blood pressure (SBP) in the control group after 1 and 2 h of acute BSO (1.4 mmol/kg, i.v.) treatment. In the L-NAME group, SBP increased significantly by 10% after 2 h of acute BSO treatment. In the BSO group, SBP did not change vs control; however, after 2 h of acute L-NAME (10 mg/kg, i.v.) treatment, the increase in SBP exceeded by 12% (P<0.05) that of the control group. Along with the increase in SBP, acute BSO treatment significantly potentiated the decrease in plasma nitrite/nitrate concentration in the L-NAME group. The acute BSO-induced glutathione decrease was significantly greater in the L-NAME group than in the control group. In NO-deficient hypertensive rats, the results are indicative of a decrease in glutathione synthesis and a stabilizing role of glutathione.     

Co-administration of glutathione and nitric oxide enhances insulin sensitivity in Wistar rats

The liver modulates insulin sensitivity through a prandial-dependent mechanism that requires activation of the hepatic parasympathetic nerves, hepatic nitric oxide (NO) and hepatic glutathione (GSH). We tested the hypothesis that co-administration of GSH and NO to the liver enhances insulin sensitivity in a GSH and NO dose-dependent manner. 24 h fasted Wistar rats were used. Hepatic GSH was supplemented by administration of glutathione monoethylester (GSH-E; 0.1/0.25/0.5/1/2 mmol kg(-1)) and 3-morpholinosidnonimine (SIN-1; 5/10 mg kg(-1)) was used as a NO donor. The drugs were administered either systemically (i.v.) or intraportally (i.p.v.). Insulin sensitivity was assessed using a transient euglycemic clamp. Neither GSH-E nor SIN-1 increased insulin sensitivity when administered alone, both i.v. and i.p.v. Moreover, changes in insulin sensitivity were not observed when GSH-E was administered i.v. followed by either i.v. or i.p.v. SIN-1 at any of the doses tested. However, i.p.v. administration of GSH-E followed by i.p.v. SIN-1 10 mg kg(-1) significantly increased insulin sensitivity in a GSH-E dose-dependent manner: 26.1+/-9.4% after 0.1 mmol kg(-1) GSH-E; 44.6+/-7.9% after 0.25 mmol kg(-1) GSH-E; 59.4+/-15.1% after 0.5 mmol kg(-1) GSH-E; 138.9+/-12.7% after 1 mmol kg(-1) GSH-E and 117.3+/-29.2% after a dose of 2 mmol kg(-1) (n = 23, P<0.005). Our results confirm that insulin sensitivity is enhanced in a dose-dependent manner by co-administration of NO and GSH donors to the liver.     

An essential role of endothelium-derived nitric oxide in vasorelaxations induced by black tea polyphenols

Green tea has received much attention as protective agent against cardiovascular disease and cancer,the two primary targets of preventive medicine.Since our first demonstration in 1999 of the involvement of endothelium-derived nitric oxide in the acute vasodilator effect of green tea polyphenols,several new vascular protective effects of green tea catechins have been identified.Theaflavins are another class of polyphenol pigments found in black tea,however,little is known about their bioactivity in the vascular system.We have recently demonstrated that black tea and its theaflavins cause relaxations of rat aortas via endothelial nitric oxide-dependent mechanisms and the tea polyphenols are very effective in protecting endothelial function agonist oxidative stress.The present results support the vascular benefit of consumption of black tea,which is equal to that of drinking green tea in terms of their endothelial cell protection and antioxidant capacity.     

Role of nitric oxide in catalepsy and hyperthermia in morphine-dependent rats

The possible involvement of nitric oxide (NO) in morphine-induced catalepsy and hyperthermia was studied in morphine-dependent rats. Four days repeated injection regimen was used to induce morphine dependence, which was assessed by naloxone challenge (0.5 mg x kg(-1), s.c.). Pretreatment of rats with the NO synthase inhibitor, N(G)-nitro-L-arginine (L-NA, 8 mg x kg(-1) twice daily, i.p.) potentiated the cataleptic response of morphine as shown by a rightward shift in the morphine-log dose-response curve. Prior treatment of rats with the NO precursor, L-arginine (200 mg x kg(-1), twice daily, i.p.) abolished the potent effect of L-NA and restored the cataleptic scores to levels similar to those of morphine-dependent rats. The same dose of L-NA significantly blocked morphine-induced hyperthermia at the dose levels of morphine (15-105 mg x kg(-1)) and this effect was reversed by L-arginine. These data provide the first experimental evidence that NO is involved in morphine induced catalepsy and hyperthermia and demonstrated that blockade of NO synthesis may suggest a dangerous interaction with opioids in the control of motor function.     

一氧化氮在顺铂致大鼠肾损害过程中的作用

目的 探讨一氧化氮在顺铂肾毒性氧化应激机制中的作用。方法 采用少量多次给大鼠腹腔注射顺铂（ＣＰ）及经口给予水飞蓟素（ＳＢ）预处理后给予ＣＰ模型,观察血尿素氮（ＢＵＮ）含量、一氧化氮合酶（ＮＯＳ）活性、丙二醛（ＭＤＡ）形成、超氧化物歧化酶（ＳＯＤ）活性等指标的变化。结果 ＣＰ可诱导ＮＯＳ活性增高,使ＮＯ生成量增多;ＢＵＮ含量与ＭＤＡ含量及ＳＯＤ活性的变化并不完全一致,而与ＮＯ含量的时相变化活性增高,     

Role of glutathione modulation in acrylonitrile-induced gastric DNA damage in rats

 Acrylonitrile (VCN) or its reactive metabolites irreversibly interact with gastric DNA in vivo and cause DNA damage. The effect of glutathione (GSH) modulation on VCN-induced genotoxicity and unscheduled DNA repair synthesis (UDRS) in DNA of gastric mucosal tissues was investigated. VCN-induced UDRS was determined: in control rats, rats with depleted gastric GSH contents, and rats treated with sulfhydryl compounds. A single oral dose (23 mg/kg) of VCN induced a time-and dose-dependent increase in gastric UDRS and decrease in GSH levels. While maximal UDRS in gastric mucosa was observed 2 h following oral administration of 23 mg/kg VCN, maximal GSH depletion (50% of control) was detected 4 h following treatment. Increasing the VCN dose to 46 mg/kg caused a further decrease in gastric GSH level (27% of control), while UDRS was elevated. Inhibition of VCN oxidation by treatment of the animals with the cytochrome P450 inhibitor, SKF 525-A, prior to VCN administration caused 65% reduction in VCN-induced UDRS. Treatment of rats with the GSH depletor diethylmaleate (DEM) prior to VCN administration caused 167% increase in UDRS in gastric mucosal tissues. Treatment of the animals with the sulfhydryl compounds, cysteine and penicillamine, prior to VCN administration protected against VCN-induced UDRS. The results demonstrated an inverse and highly significant correlation between gastric GSH levels and VCN-induced UDRS (r=−0.873, P<0.0001). In conclusion, our study indicates that VCN bioactivation and the homeostasis of gastric GSH may play a major role in the initial processes underlying VCN-induced gastric carcinogenesis. Received: 24 January 1996/Accepted: 9 April 1996     

Modulation of stress-induced neurobehavioral changes by nitric oxide in rats

The involvement of nitric oxide (NO) in stress-induced neurobehavioral changes in rats was evaluated using the elevated plus maze and open field tests. Restraint stress (1 h) reduced both the number of entries and time spent in open arms, with both expressed as percent of controls (no restraint stress), and these changes were reversed with diazepam (1 mg/kg) and the NO precursor, L-arginine (500 and 1000 mg/kg) pretreatment. The nitric oxide synthase inhibitor, N-nitro-L-arginine methyl ester (L-NAME) (50 mg/kg), aggravated restraint stress effects in the elevated plus maze test, whereas the lower dose (10 mg/kg) of the drug attenuated the same. In the open field test, the restraint stress-induced (a) increased entry latency and (b) decreased ambulation and rearing were reversed by diazepam and L-arginine and L-NAME (10 mg/kg), whereas L-NAME (50 mg/kg) aggravated restraint stress effects. The neuronal nitric oxide synthase inhibitor, 7-nitroindazole (10 and 50 mg/kg), did not influence these restraint stress-induced behavioral changes to any significant extent. Biochemical data showed that L-NAME (10 and 50 mg/kg.) induced opposite effects on the total brain nitrate/nitrite content during restraint stress. The results indicate a possible involvement of NO in stress-induced neurobehavioral effects.     

Role of nitric oxide in the gastric cytoprotection induced by central vagal stimulation

The role of nitric oxide (NO) in the vagal cholinergic-mediated cytoprotective effect of intracisternal (i.c.) injection of the stable thyrotropin-releasing hormone (TRH) analog, RX 77368, was investigated in conscious rats. RX 77368 (1.5 ng i.c.) reduced by 88% gastric hemorrhagic lesions induced by oral administration of ethanol (60%). L-N^G-Nitro-arginine methyl ester (L-NAME, 3 mg/kg i.v.), an inhibitor of NO synthase, abolished the cytoprotection provided by i.c. RX 77368. The effect of L-NAME was reversed by L- but not D-arginine. These results suggest that the L-arginine-nitric oxide pathway is involved in the cytoprotective effect of i.c. TRH analog, probably through the modulation of gastric mucosal blood flow.     

Role of nitric oxide in electroshock and pentylenetetrazole seizure threshold in rats

There are contradictory reports on whether nitric oxide (NO) is a proconvulsant or anticonvulsant. Hence a study was designed to investigate the effect of NO donor l-Arginine and NO synthesis inhibitor N omega-nitro-L-arginine (NOARG) on electroshock- and pentylenetetrazole (PTZ)-induced seizure threshold in rats. L-arginine was tested in three doses (75, 150 and 300 mg/kg), and NOARG was administered in doses of 4, 8 and 16 mg/kg. L-Arginine increased the intensity of current required to produce a threshold seizure, whereas NOARG had the opposite effect. In PTZ-induced seizures, L-arginine significantly decreased the dose of PTZ required to produce a threshold seizure, while NOARG increased it. Hence, it was concluded that NO synthase inhibition had the opposite effect in electroshock- and PTZ-induced seizures, meriting further studies on the mechanism of effect.     

Antroduodenal motility and gastric emptying. Gastroduodenal motility and pH following ingestion of paracetamol

The influence of paracetamol on antroduodenal motility and gastric pH was studied in 11 healthy subjects and the relationship between gastroduodenal motility and gastric emptying rate time, tmax, to peak concentration of serum paracetamol, Cmax, was evaluated. The incidence of antral phase III activity and the duration of phase III was diminished with paracetamol (P less than 0.05). The other motility parameters assessed were unchanged. Three patterns of motility and absorption were observed. One group (n = 5) were fast absorbers with a tmax of 1 h and a motility pattern characterized by antral activity, a high motility index and a short duration of phase II (33-60 min); the phase IIIs were complete except in one case. The second group (n = 4) had tmax at 1.5 h and their phase II motility was characterized by a longer duration (80-133 min) (P less than 0.05), by antral activity, and by a high motility index; their phase IIIs were all incomplete. The last group (n = 2) were slow absorbers: Cmax was not reached in the investigation period, no antral contractions were seen, and the motility index was low. The area under the serum-concentration curve of paracetamol differed between the groups at 90 and 180 min (P less than 0.01).     

Role of nitric oxide in experimental models of psychosis in rats

The aim of our study was to investigate the effects of the NO precursor L-arginine and the nitric oxide synthase inhibitor N omega-nitro-L-arginine (L-NORAG) on amphetamine-induced stereotypy, haloperidol-induced catalepsy and conditioned avoidance response (CAR) in rats. Amphetamine (3 mg/kg i.p.) was used for the induction of stereotypy, while for the induction of catalepsy and CAR, haloperidol (2 mg/kg i.p.) was used. This study was divided into 2 parts--acute administration of L-arginine (150 mg/kg i.p.) and L-NOARG (50 mg/kg i.p.) and chronic administration of L-arginine (150 mg/kg/day i.p.) and L-NOARG (50 mg/kglday i.p.) for 5 days. We found that L-arginine inhibited amphetamine-induced stereotypy and haloperidol-induced catalepsy, but intensified CAR. On the other hand, L-NOARG intensified stereotypy and catalepsy but inhibited CAR. Also, there was no significant difference between the scores of acute and chronic administration of L-arginine and L-NOARG. It is concluded from our study that nitric oxide produces conflicting results on various models of psychosis. L-arginine might be useful as an antipsychotic without causing extrapyramidal symptoms.