Protective effects of crocin against cisplatin-induced acute renal failure and oxidative stress in rats

Background. The major side effect of cisplatin, used in some tumours, is nephrotoxicity. Reactive oxygen species and oxidative damage are the most important factors in cisplatin-induced acute renal failure. The main purpose of this study is to investigate the protective effects of crocin against cisplatin-induced acute renal failure and oxidative stress in rat. Methods. In this study, animals were randomly divided into 5 groups (6 each). Group one received normal saline (2 ml/day, i.p.). Group two received a single dose of cisplatin (5 mg/kg, i.p.). Groups 3 to 5 received crocin (100, 200 and 400 mg/kg, i.p., respectively, for 4 consecutive days one hour before a single dose of cisplatin (5 mg/kg) only at the first day. Blood samples were taken out (on the fifth day) for measuring the level of urea and creatinine. The kidneys were removed for histopathological and biochemical examinations. Furthermore, 24-hour urinary factors were measured. Results. Blood urea, creatinine and urinary glucose and protein concentrations in crocin-treated groups were significantly lower than those of cisplatin-treated group in a dose-dependent manner. Histopathological studies showed a massive damage in S3 segment of proximal tubules in cisplatin-treated group. No damage was observed in crocin-treated groups. Crocin treatment resulted in a significant and dose-dependent reduction in malondialdehyde concentration as compared to the cisplatin-treated group. Moreover, crocin produced a significant elevation in total thiol and glutathione peroxidase concentrations, as compared with cisplatin-treated group. Conclusion. The results of the present study suggest that crocin has a protective effect against cisplatin-induced acute renal failure and relative oxidative stress.     

Comparative study of the effects of gentamicin, neomycin, streptomycin and ofloxacin antibiotics on sperm parameters and testis apoptosis in rats

The aim of this study was to investigate the comparative effects of aminoglycosides and fluoroquinolones on testis apoptosis and sperm parameters in rats. Fifty male Wistar rats were randomly divided into control (n = 10) and experimental (n = 40) groups. The experimental groups subdivided into four groups often. Each received 5 mg kg(-1) (IP) gentamicin, 50 mg kg(-1) (IP) neomycin, 40 mg kg(-1) (IP) streptomycin and 72 mg kg(-1) (IP) ofloxacin daily for 14 days, respectively; however, the control group just received vehicle (IP). In the fourteenth day, rats were killed and sperm analyzed for sperm parameters. Testis tissues were also prepared for TUNEL assay for detection of apoptosis. There was a significant decrease in sperm count, viability and motility in all of experimental groups when compared with control group. Although in streptomycin group these parameters were less decreased than in the other experimental groups. The apoptotic cells were significantly increased in all experimental groups when compared with those seen in the controlled group. Gentamicin, neomycin and streptomycin and ofloxacin have negative effects on sperm parameters and testis apoptosis in rats. However, these side effects are less seen in the streptomycin group. Therefore, it is recommended that usage of this drug have fewer side effects on male fertility.     

Effects of Atorvastatin on the Hypertension-Induced Oxidative Stress in the Rat Brain

Background: It is well known that the development of brain oxidative stress is one of the most serious complications of arterial hypertension that evokes brain tissue damage. The aim of this study was to examine the effects of atorvastatin treatment (20 mg/kg/day), as an antioxidant, to prevent the brain tissue oxidative stress in the hypertensive (HTN) rats. Methods: Experiments were performed in four groups of rats (n = 5 each group): sham, sham-treated, HTN and HTN treated. Rats were made HTN by aortic constriction above the renal arteries. After 30 days, rats were slaughtered under deep anesthesia to remove brain hemispheres. After tissue homogenization, enzyme activities of superoxide dismutase (SOD) and catalase (CAT), as well as glutathione (GSH) content and malondialdehyde (MDA) level were determined by biochemical methods. Results: In HTN rats, arterial blood pressure was increased about 40% and brain enzyme activities of SOD and CAT were significantly decreased compared with sham group. Induction of hypertension significantly decreased GSH content and increased MDA level of brain tissue. Treatment with atorvastatin enhanced the activity of SOD and prevented from GSH decrement during hypertension. Conclusion: Based on the findings of this study, treatment with atorvastatin might have saved the brain tissue of HTN rats from hypertension-induced oxidative stress. Key Words: Atorvastatin, Aortic coarctation, Oxidative stress, Hypertension     

Chronic Nicotine Toxicity is Prevented by Aqueous Garlic Extract

Based on the potent antioxidant effects of garlic, we investigated the putative protective role of aqueous garlic extract (AGE) against nicotine-induced oxidative organ damage. Male Wistar albino rats (200–250 g) were injected with nicotine hydrogen bitartrate (0.6 mg/kg; i.p.) alone or with aqueous garlic extract (125 mg/kg; i.p.) for 21 days. At the end of the experimental period (22^nd day) rats were killed by decapitation. The aorta, heart, kidney and urinary bladder tissues were taken for the determination of malondialdehyde (MDA) and glutathione (GSH) levels, myeloperoxidase (MPO) activity and collagen contents. Blood urea nitrogen (BUN) and creatinine concentrations and lactate dehydrogenase (LDH) levels in blood were measured for the evaluation of renal functions and tissue damage, respectively. Tissues were also examined microscopically.The decrease in GSH levels and increases in MDA level, MPO activity and collagen contents induced by chronic nicotine administration indicated that tissue injury involves free radical formation. Treatment of rats with AGE restored the reduced GSH levels while it decreased MDA levels as well as MPO activity. Increased collagen contents of the tissues by chronic nicotine were reversed back to the control levels with AGE. Since AGE administration reversed these oxidant responses, improved renal function and histological damage, it seems likely that AGE protects the tissues against nicotine-induced oxidative damage.     

Protective Effects of Fucoxanthin on Hydrogen Peroxide-Induced Calcification of Heart Valve Interstitial Cells

Cardiovascular diseases such as atherosclerosis and aortic valve sclerosis involve inflammatory reactions triggered by various stimuli, causing increased oxidative stress. This increased oxidative stress causes damage to the heart cells, with subsequent cell apoptosis or calcification. Currently, heart valve damage or heart valve diseases are treated by drugs or surgery. Natural antioxidant products are being investigated in related research, such as fucoxanthin (Fx), which is a marine carotenoid extracted from seaweed, with strong antioxidant, anti-inflammatory, and anti-tumor properties. This study aimed to explore the protective effect of Fx on heart valves under high oxidative stress, as well as the underlying mechanism of action. Rat heart valve interstitial cells under H₂O₂-induced oxidative stress were treated with Fx. Fx improved cell survival and reduced oxidative stress-induced DNA damage, which was assessed by cell viability analysis and staining with propidium iodide. Alizarin Red-S analysis indicated that Fx has a protective effect against calcification. Furthermore, Western blotting revealed that Fx abrogates oxidative stress-induced apoptosis via reducing the expression of apoptosis-related proteins as well as modulate Akt/ERK-related protein expression. Notably, in vivo experiments using 26 dogs treated with 60 mg/kg of Fx in combination with medical treatment for 0.5 to 2 years showed significant recovery in their echocardiographic parameters. Collectively, these in vitro and in vivo results highlight the potential of Fx to protect heart valve cells from high oxidative stress-induced damage.     

Dietary Supplementation of Almond Prevents Oxidative Stress by Advocating Antioxidants and Attenuates Impaired Aversive Memory in Male Rats

Scopolamine, an anti-muscarinic agent, has been shown to induce amnesia and oxidative stress similar to that observed in the older age. The present study was designed to determine the relationship between the oxidative status and memory improvement in scopolamine injected rats pre-administered with almonds. Rats (n?=?8) in the almond group were administered orally with 400 mg/kg almond suspension for 28 days daily before the intraperitoneal injection of scopolamine (0.5 mg/kg). Passive avoidance task (PAT) was used to assess memory function at the end of treatment. The present study revealed that scopolamine injection significantly impaired the memory function in rats pre-treated with saline which was accompanied by increased oxidative stress as evident by increased brain malondialdehyde (MDA) levels and reduced activities of antioxidant enzymes as compared to healthy controls. Pre-treatment with almond significantly ameliorated scopolamine-induced oxidative stress and memory dysfunction. These findings suggest that dietary supplementation with almonds may have a beneficial effect in reducing the risk of oxidative stress-induced memory loss and delaying or preventing the onset of age-related memory impairment.     

Efficacy of echinacea on the action of cyproterone acetate in male rats

The study aimed to evaluate the effect Echinacea extract (E) on the testicular antioxidants function in normal rats or that subjected to anti-androgenic compound, cyproterone acetate (CA). Rats were divided into 5 groups treated daily via an oral tube for two intervals 2 and 4 weeks, 1st control, 2nd E (Echinacea treated group in dose 63 mg kg(-1)), 3rd CA (cyproterone acetate treated group in dose 25 mg kg(-1)), 4th E+CA and 5th E as prophylactic one week before E+CA treatment with the same aforementioned E or CA doses. The body, testes, epididymis and vas deferens weights were recorded. Sperm count, Nitric Oxide (NO), calcium ion (Ca2+) and malondialdhyde (MDA) contents in addition to superoxide dismutase (SOD), glutathione S-transferase (GST) activities were determined in testicular tissues. CA exhibited direct negative effect on reproductive organs weight and significant reducing effect on sperm count and Ca2+ contents. SOD and GST activities significantly decreased in addition to significant increase in NO, MDA contents reflecting the oxidative status of testis in CA treated rats. The prophylactic effect of E treatment, in time related manner, showed significant improvement in the antioxidant status of the testicular tissue which is more pronounced as compared to E+CA treatment.     

Marine-Derived Penicillium purpurogenum Reduces Tumor Size and Ameliorates Inflammation in an Erlich Mice Model

Background: This study addresses the antitumoral properties of Penicillium purpurogenum isolated from a polluted lagoon in Northeastern Brazil. Methods: Ethyl Acetate Extracellular Extract (EAE) was used. The metabolites were studied using direct infusion mass spectrometry. The solid Ehrlich tumor model was used for antitumor activity. Female Swiss mice were divided into groups (n = 10/group) as follows: The negative control (CTL−), treated with a phosphate buffered solution; the positive control (CTL+), treated with cyclophosphamide (25 mg/kg); extract treatments at doses of 4, 20, and 100 mg/kg; animals without tumors or treatments (Sham); and animals without tumors treated with an intermediate dose (EAE20). All treatments were performed intraperitoneally, daily, for 15 days. Subsequently, the animals were euthanized, and the tumor, lymphoid organs, and serum were used for immunological, histological, and biochemical parameter evaluations. Results: The extract was rich in meroterpenoids. All doses significantly reduced tumor size, and the 20 and 100 mg/kg doses reduced tumor-associated inflammation and tumor necrosis. The extract also reduced the cellular infiltration of lymphoid organs and circulating TNF-α levels. The extract did not induce weight loss or renal and hepatic toxic changes. Conclusions: These results indicate that P. purpurogenum exhibits immunomodulatory and antitumor properties in vivo. Thus, fungal fermentation is a valid biotechnological approach to the production of antitumor agents.     

Toxic effects of domoic acid in the seabream Sparus aurata

Neurotoxicity induced in fish by domoic acid (DA) was assessed with respect to occurrence of neurotoxic signs, lethality, and histopathology by light microscopy. Sparus aurata were exposed to a single dose of DA by intraperitoneal (i.p.) injection of 0, 0.45, 0.9, and 9.0 mg DA kg(-1) bw. Mortality (66.67 ± 16.67%) was only observed in dose of 9.0 mg kg(-1) bw. Signs of neurological toxicity were detected for the doses of 0.9 and 9.0 mg DA kg(-1) bw. Furthermore, the mean concentrations (±SD) of DA detected by HPLC-UV in extracts of brain after exposure to 9.0 mg DA kg(-1) bw were 0.61 ± 0.01, 0.96 ± 0.00, and 0.36 ± 0.01 mg DA kg(-1) tissue at 1, 2, and 4 hours. The lack of major permanent brain damage in S. aurata, and reversibility of neurotoxic signs, suggest that lower susceptibility to DA or neuronal recovery occurs in affected individuals.     

Antidiabetic effect of essential oil from Artemisia sieberi growing in Jordan in normal and alloxan induced diabetic rats

The aim of this study was to evaluate the effects of essential oil extracted from aerial parts of Artemisia sieberi in normal and alloxan induced diabetic rats. Fifty rats were divided into five groups of 10 each. Group I normal rats received 1 mL day(-1) of dimethyl sulfoxide (control); group II normal rats received a single dose (80 mg kg(-1) b.wt.) of essential oil extract of Artemisia sieberi; group III diabetic rats received 1 mL day-of dimethyl sulfoxide; group IV diabetic rats received the oil extract (80 mg kg(-1) b.wt.); group V diabetic rats received metformin (14.2 mg kg(-1) b.wt.). All treatments were orally administered once a day for six weeks. Changes in blood glucose concentration, body weight and food and water intake were measured and the data obtained were compared with that of metformin. The essential oil extract significantly (p < 0.05) lowered blood glucose level as well as food and water intake in diabetic rats accompanied by an increase in body weight gain with no apparent side effect when compared with untreated diabetic rats. These effects were found to be closely similar to that of metformin, a common antidiabetic drug. On other hand, no apparent improvement on body weight gain in diabetic rats treated with metformin. In addition, for all parameters measured, the oil extract showed no effect in normal rats. In conclusion, the essential oil of Artemisia sieberi exhibited antidiabetic activity in alloxan-induced diabetic rats. Present findings support the possible use of the essential oil of Artemisia sieberi as a remedy for diabetes mellitus in humans.     

Influences of Fucoxanthin on Alveolar Bone Resorption in Induced Periodontitis in Rat Molars

The aim of this study was to evaluate the effects of systemic fucoxanthin treatment on alveolar bone resorption in rats with periodontitis. Thirty rats were divided into control, experimental periodontitis (EP), and experimental periodontitis-fucoxanthin (EP-FUCO) groups. Periodontitis was induced by ligature for four weeks. After removal of the ligature, the rats in the EP-FUCO group were treated with a single dose of fucoxanthin (200 mg/kg bw) per day for 28 consecutive days. At the end of the study, all of the rats were euthanized and intracardiac blood and mandible tissue samples were obtained for biochemical, immunohistochemical, and histometric analyses. Fucoxanthin treatment resulted in a slight decrease in tumor necrosis factor-α, interleukin-1β, and interleukin-6 levels and a significant decrease in oxidative stress index. It was observed that fucoxanthin caused a significant reduction in receptor activator of nuclear factor kappa-β ligand (RANKL) levels and a statistically non-significant elevation in osteoprotegerin and bone-alkaline phosphatase levels. There were no significant differences in alveolar bone loss levels between the EP and EP-FUCO groups. This experimental study revealed that fucoxanthin provides a limited reduction in alveolar bone resorption in rats with periodontitis. One of the mechanisms underlying the mentioned limited effect might be related to the ability of fucoxanthin to inhibit oxidative stress-related RANKL-mediated osteoclastogenesis.     

Effect of Diet Supplemented with Quinoa Seeds on Oxidative Status in Plasma and Selected Tissues of High Fructose-Fed Rats

Oxidative stress plays an important role as a mediator of damage produced by fructose metabolism. This work was designed to investigate the effect of diet supplemented with quinoa seeds on oxidative stress in plasma, heart, kidney, liver, spleen, lung, testis and pancreas of fructose administered rats. Fructose administration (310 g/kg fodder for 5 weeks) caused oxidative stress that was manifested by the increase in plasma malondialdehyde (MDA) (p<0.05), and by the non-significant changes in the enzymatic antioxidant potential in plasma and most of tissues. Co-administration of quinoa seeds (310 g/kg fodder) maintained normal activities of some enzymes. It also influenced the oxidative stress as was evidenced by decreasing MDA in plasma, and decreasing the activities of antioxidant enzymes (erythrocyte superoxide dismutase - eSOD, catalase -CAT, plasma glutathione peroxidase - pGPX). These findings demonstrate that quinoa seeds can act as a moderate protective agent against potential of fructose-induced changes in rats by reducing lipid peroxidation and by enhancing the antioxidant capacity of blood (plasma) and heart, kidney, testis, lung and pancreas.     

Effect of hydroalcoholic extract of Lavandula officinalis on nicotine-induced convulsion in mice

Epilepsy an important CNS (central nervous system) problem that about 1% of world's population suffer of it. The aim of study was to evaluate of anticonvulsant effect of hydroalcoholic extract of Lavandula officinalis. In this study, anticonvulsant activity of the hydroalcoholic extract of Lavandula officinalis (L. officinalis) was studied against chemoconvulsant-induced seizures in male mice. Lavandula officinalis (100, 200, 400, 600 and 800 mg kg(-1)), diazepam (0.15 mg kg(-1)) and normal saline (10 mL kg(-1)) were injected intraperitoneally, respectively in different groups of mice, 30 min before nicotine (5 mg kg(-) i.p.). The onset time intensity and duration of convulsions and the percentage of death were recorded. Also the time-response (0, 15, 30, 45, 60 min before nicotine injection) for most effective dose of plant extract (600 mg kg(-1)) was investigated. The results showed that hydroalcoholic extract of Lavandula officinalis had anticonvulsant effect. The most effective dose of plant extract was 600 mg kg(-1). In time-response study for the most effective dose of extract (600 mg kg(-1)), the onset, duration and intensity of convulsion significantly (p < 0.05) increased, decreased and decreased, respectively for all tested times. The best response observed in 30, 45 and 60 min. The results showed significant anticonvulsant effect for hydroalcoholic extract of Lavandula.     

Effects of Polygonum aviculare herbal extract on sperm parameters after EMF exposure in mouse

Electromagnetic fields with high energy same as ionizing radiation inserts their destructive effects via free radical production. Using antioxidants or herbal plants with antioxidants components could diminish hazardous effects of EMF. Polygonum aviculare has a high amount of phenolic and flavonoid and proved that has antioxidants effects. The aim of this study was to evaluate the effects of Polygonum aviculare herbal extract on sperm parameters after EMF exposure in mouse. Twenty four male mice, 8 weeks divided to 4 groups (one control and three experimental groups). Control group didn't receive EMF exposure. EMF group mice received 3 mT EMF during 2 months, 4 h daily and 5 days weekly. Polygonum aviculare group received 50 mg kg(-1) herbal extract during 2 months and poly -EMF group received 3 mT EMF during 2 months, 4 h daily and 5 days weekly and 50 mg kg(-1) herbal extract during 2 months. After 2 months the mice sacrificed with cervical dislocation and sperm obtained from tail of epididymis and motility and morphology of them were analyzed. Sperm analysis results showed that in group with Polygonum aviculare, morphology and motility of sperm developed (p < 0.05). Present results showed that EMF can reduce motility of sperm and treatment of Polygonum aviculare after EMF exposure developed sperm quality after EMF exposure.     

The study of antinociceptive effect of hydroalcoholic extract of Teucrium oliverianum (a plant used in southern Iranian traditional medicine) in rat by formalin test

Objective: Antinociceptive and anti-inflammatory activities of hydroalcoholic extract of Teucrium Oliverianum were investigated by formalin test model. This study was conducted in on the male Wistar rats, weighting 150-180 g. The animals were divided into seven groups (n = 7) and received 200, 400, 600 and 800 mg kg(-1) of hydroalcoholic extract of teucrium oliverianum intraperitoneally, respectively. Negative control group received normal saline (5 mL kg(-1)) and the positive control groups received 2.5 mg kg(-1) morphine and 300 mg kg(-1) aspirin, intraperitoneally respectively. The results showed that all doses of extract have significant analgesic effect (p < 0.05) in all studies times in comparison with negative control. The best result achieved with 600 mg kg(-1) of extract. The result revealed that the analgesic effect of the extract (600 mg kg(-1)) \was less than aspirin (300 mg kg(-1)) on the second phase of pain and less than morphine (2.5 mg kg(-1)) in both phases of the pain, more than aspirin in first phase of pain. One group of animals was treated with naloxone (1 mg kg(-1), i.p.) and suitable dose of extract (600 mg kg(-1), i.p.). Also, Naloxone inhibited analgesic effect of alcoholic extract of Teucrium Oliverianum. It can be concluded that the alcoholic extract of Teucrium oliverianum may exert its effect through opioid receptors, stimulating GABAergic system or promotes the release of endogenous opipeptides or decreasing free radicals.     

绿茶多酚对被动吸烟引起小鼠肺氧化应激的干预研究

研究了绿茶多酚（Green tea polyphenol,GTP）对被动吸烟致小鼠肺部氧化应激损伤的干预作用,并探讨其可能机制。将40只KM雌性小鼠随机分成正常对照C组、被动吸烟模型M组、100βmg·kg^-1 GTP1组、200βmg·kg^-1 GTP2组,每组10只。实验12周结束后处死小鼠,测定其肺质量及血清氧化应激炎症水平;采用荧光定量PCR测定白细胞介素6（IL-6）、白细胞介素33（IL-33）、肿瘤坏死因子-α（TNF-α）和白细胞介素1β（IL-1β）基因表达水平。研究结果表明,与M组相比,灌喂GTP后使得小鼠生存质量、肺形态有明显改观,显著提高小鼠血清T-SOD及GSH-Px活力,显著降低MDA、IL-6、TNF-α表达水平,显著抑制IL-6、IL-33、TNF-α及IL-1β炎性相关基因的表达,灌胃200βmg·kg^-1 GTP比100βmg·kg^-1的GTP作用更加显著。研究发现,GTP可能通过抑制炎性细胞因子表达水平、提高抗氧化能力来保护肺部组织形态与结构的完整,保护被动吸烟对肺部的损害。     

Morphological alteration in mitochondria following diclofenac and ibuprofen administration

This study was conducted to identify and to compare the mitochondrial morphological alterations in livers of rats treated with various doses of diclofenac and ibuprofen. Hundred and forty-four male Sprague Dawley rats were dosed with 3, 5 and 10 mg kg(-1) diclofenac and ibuprofen in saline via intraperitoneal injection for 15 days. The control group was administered with saline in a similar manner. Four rats were euthanised every 3 days until day 15. While 200 mg kg(-1) diclofenac and ibuprofen-treated rats (n = 4) were euthanized 10 h posttreatment. The livers were removed, cleaned and a section across the right lobe was taken and fixed in 4% (v/v) glutaraldehyde for electron microscopy analysis and the remaining samples were kept at -80 degrees C for Western blot analysis. Five milligram per kilogram and 10 mg kg(-1) diclofenac-administered rats for 15 days revealed the presence of enlarged mitochondria, irregular and ruptured mitochondrial membranes. While rats administered with 10 mg kg(-1) ibuprofen also showed the presence of mitochondria with irregular membrane structure and ruptured membranes. Western blotting analysis of mitochondrial fractions revealed the expression of cytochrome c in all samples and complete absence of cytochrome c expression in the cytosolic fraction of all samples after day 15. Analysis in 200 mg kg(-1) diclofenac and ibuprofen-treated groups, revealed expression of cytochrome c in both mitochondrial and cytosolic fractions. This observation indicates that both diclofenac and ibuprofen may alter the morphology of mitochondria, leading to cytochrome c release into the cytosol. Further studies needs to be conducted to investigate on the activity of the mitochondria following both treatments.     

Effect of grape seed extract on lead induced hypertension and heart rate in rat

The main objective of this study was to evaluate the potential protective effect of red Grape Seed Extract (GSE) on lead induced hypertension (HTN) and Heart Rate (HR) in male Wistar rats. The rats were randomly assigned to one of 4 groups: Each group received lead acetate (100 ppm in drinking water), GSE (100 mg kg(-1), orally) or Lead + GSE for 45 days. Another group assigned as control group provided with tap water and regular pellet food. The Systolic Blood Pressure (SBP) and heart rate were determined by tail plethysmography coupled to a computer system. There was a sustained elevation of SBP in lead exposed rats that significantly increased at day 18 (lead treated, 112.7 +/- 2.7 mmHg, vs. control, 105.6 +/- 2.6 mmHg, n = 10, p < 0.05) and reached a maximum level at day 36 (lead treated, 124.9 +/- 2.3 mmHg, vs. control, 103.6 +/- 3.1 mmHg, n = 10, p < 0.001). However, the other three groups; showed no significant changes in SBP. Furthermore, the heart rate was increased sustainly in lead exposed animals that was statistically significant at days 36 and 45 (lead treated group, 404.5 +/- 9.4 vs. control group, 381.7 +/- 6.7, n = 10, p < 0.05). The blood lead level in both lead and lead + GSE treated groups was increased significantly compared with control and GSE treated groups (p < 0.001). However, GSE administration had no effect on the blood lead level in lead treated group. According to the result of this study, it may be concluded that GSE could have beneficial effect in protecting the cardiovascular system through its antioxidant activity against oxidative stress.     

Sulfated-polysaccharide fraction from red algae Gracilaria caudata protects mice gut against ethanol-induced damage

The aim of the present study was to investigate the gastroprotective activity of a sulfated-polysaccharide (PLS) fraction extracted from the marine red algae Gracilaria caudata and the mechanism underlying the gastroprotective activity. Male Swiss mice were treated with PLS (3, 10, 30 and 90 mg·kg(-1), p.o.), and after 30 min, they were administered 50% ethanol (0.5 mL/25 g(-1), p.o.). One hour later, gastric damage was measured using a planimeter. Samples of the stomach tissue were also obtained for histopathological assessment and for assays of glutathione (GSH) and malondialdehyde (MDA). Other groups were pretreated with l-NAME (10 mg·kg(-1), i.p.), dl-propargylglycine (PAG, 50 mg·kg(-1), p.o.) or glibenclamide (5 mg·kg(-1), i.p.). After 1 h, PLS (30 mg·kg(-1), p.o.) was administered. After 30 min, ethanol 50% was administered (0.5 mL/25 g(-1), p.o.), followed by sacrifice after 60 min. PLS prevented-ethanol-induced macroscopic and microscopic gastric injury in a dose-dependent manner. However, treatment with l-NAME or glibenclamide reversed this gastroprotective effect. Administration of propargylglycine did not influence the effect of PLS. Our results suggest that PLS has a protective effect against ethanol-induced gastric damage in mice via activation of the NO/K(ATP) pathway.