Inhibition by dietary hydroquinone of acetylaminofluorene induction of initiation of rat liver carcinogenesis.

Monocyclic phenolics (MPs) occur widely in foods, both naturally and as synthetic antioxidant additives. Several have been shown to inhibit the carcinogenicity of a variety of genotoxic carcinogens in various tissues. Hydroquinone (HQ), one of the simplest of the MPs, which occurs naturally as the glucose conjugate arbutin, was studied for its ability, at low dietary levels, to inhibit the initiating effects in the rat liver of the DNA-reactive carcinogen 2-acetylaminofluorene (AAF). Male Fischer 344 rats (F344), 8 weeks old at the start of the study, were allocated to six groups. HQ was fed daily ad libitum in PMI certified diet at either 0.05% (approximately 25 mg/kg bw/d) or 0.2% (approximately 100 mg/kg bw/d) for 13 weeks, starting one week before AAF administration was initiated, and at the same doses to two groups not receiving AAF. AAF was given intragastrically three times a week for 12 weeks at doses of 3mg/kg bw in 0.5% carboxymethyl cellulose (CMC) to a basal diet group and two of the groups receiving HQ in the diet. Vehicle controls were fed basal diet and administered 0.5% CMC intragastrically three times a week. The rats were observed daily and body weights were taken before initial dosing and at weekly intervals thereafter. Body weight gain over time, terminal body weights and absolute (mg) and relative liver weights (relative to body weight) were measured. At the end of the study (13 weeks), DNA adducts ((32)P-postlabeling), cell proliferation (PCNA immunohistochemistry) and preneoplastic hepatocellular altered foci (HAF) (glutathione S-transferase-placental type immuno-histochemistry) were measured. No significant differences were observed in body weight gains or liver weights. AAF produced liver DNA adducts and at the low dose of HQ adduct levels were 90% of that for AAF alone, whereas at the high dose adducts were reduced by 33% (p<0.05). AAF exposure yielded about a 50% increase in hepatocellular proliferation and both HQ doses reduced the AAF-induced increases in proliferation by about 25%. Likewise, the AAF-induced GST-P-positive HAF per cm(2) of liver tissue were decreased by both doses of HQ by about 50%. Thus, under the conditions of this experiment, HQ at both 0.05% and 0.2% in the diet diminished AAF-induced cancer initiating effects in rat liver.     

Effects of aminothiols in 2-acetylaminofluorene-treated rats. III. Metabolic activation of aromatic amines

Six groups of Wistar rats received a standard diet supplemented with 0.05% 2-acetylaminofluorene and/or 0.1% natural (reduced glutathione) or synthetic (N-acetyl-L-cysteine) aminothiols. The discontinuous feeding regimen consisted of 4 cycles, each composed of 3 weeks of treatment followed by withdrawal for 1 week. At the 3rd and 4th week of each cycle, the liver was removed from 4-5 rats within each group, and pools of S-12 fractions were assayed for the ability to activate 2-acetylaminofluorene and other aromatic amines, either structurally related (i.e. 4-acetylaminofluorene and 2-aminofluorene) or unrelated (i.e. 2-naphtylamine and benzidine) to mutagenic metabolites in strain TA98 of S. typhimurium. In untreated rats, there was a consistent and marked trend to an age-dependent loss of metabolic activation of all test compounds during the 16 weeks of the experiment. Feeding of 2-acetylaminofluorene resulted in an evident autoinduction of metabolism which was continuously amplified with time, even during the withdrawal weeks. In the same animals, activation of the other amines was initially inhibited but then progressively shifted to a mild cross-induction which, in the case of the structurally related compounds, became significant at the end of the 4-cycle treatment with 2-acetylaminofluorene. The metabolic effects of the two aminothiols were broadly variable, depending on the thiol, on its co-administration with 2AAF, on the week and cycle of treatment, and on promutagens tested.     

Prevention of 2-acetylaminofluorene-induced loss of nuclear envelope cytochrome P450 by the simultaneous administration of 3-methylcholanthrene

Rats fed a basal diet containing 0.05% (w/w) 2-acetylaminofluorene (AAF) for 3 weeks showed a 50% loss of hepatic nuclear envelope cytochrome P450, whereas microsomal P450 remained at control levels. A similar dietary treatment with 0.004% (w/w) 3-methylcholanthrene (MC) caused moderate losses (20-25%) of cytochrome P450 in both nuclear envelopes and microsomes. Administration of the basal diet supplemented with a mixture of AAF (0.05%) plus MC (0.004%) resulted in a preservation of control levels of nuclear envelope cytochrome P450 and a 30% elevation of microsomal P450. Immunoblot analysis revealed that AAF alone, or in concert with MC, induced comparable levels of the P450d form. Induction of cytochrome P450c by dietary MC was detected only when MC was fed together with AAF. As previously found for butylated hydroxytoluene (BHT), the protective effect of dietary MC against hepatocarcinogenesis in AAF-fed rats correlated with a preservation of nuclear envelope cytochrome P450 content and with the induction of cytochrome P450c.     

The effect of combined treatment with niacin and chromium (III) chloride on the different tissues of hyperlipemic rats

We investigated the effects of a combined treatment with chromium (Cr) and niacin on the spleen, tongue, and lens tissues in terms of lipid peroxidation (LPO), glutathione (GSH), serum catalase (CAT), lactate dehydrogenase (LDH), serum cholesterol, and total lipid levels in normal and hyperlipemic rats. In this study, female 1-year-old Swiss albino rats were used. The rats were randomly divided into four groups. Group I rats (control) were fed with standard pellet chow. Group II rats were fed a lipogenic diet in which 2% cholesterol, 0.5% cholic acid, and 20% sunflower oil were added and were given 3% alcoholic water for 60 days. Group III rats were fed with the same lipogenic diet and were treated with a dose of 250 microg/kg body weight CrCI3 x 6H2O and 100 mg/kg body weight niacin, for 45 days, by gavage. The rats in group IV were fed with pellet chow and treated with 250 microg/kg body weight CrCI3 x 6H2O and 100 mg/kg body weight niacin, by gavage, for 45 days. After 2 weeks, the animals showed symptoms of hyperlipemia. On the 60th day, tissue and blood samples were taken. We have observed decreased CAT activity and GSH levels, increased LDH activity, cholesterol, total lipid, and LPO levels in hyperlipemic rats. Niacin and Cr administration to hyperlipemic rats increased tissue GSH levels and CAT activity and decreased tissue LPO levels and LDH activity, cholesterol, and total lipid levels compared with hyperlipemic rats. We conclude that the administration of a combination of niacin and chromium has a protective effect against oxidative damage to tongue, lens, and spleen tissues as a result of hyperlipemia.     

The Effect of Combined Treatment with Niacin and Chromium (III) Chloride on the Different Tissues of Hyperlipemic Rats

We investigated the effects of a combined treatment with chromium (Cr) and niacin on the spleen, tongue, and lens tissues in terms of lipid peroxidation (LPO), glutathione (GSH), serum catalase (CAT), lactate dehydrogenase (LDH), serum cholesterol, and total lipid levels in normal and hyperlipemic rats. In this study, female 1-year-old Swiss albino rats were used. The rats were randomly divided into four groups. Group I rats (control) were fed with standard pellet chow. Group II rats were fed a lipogenic diet in which 2% cholesterol, 0.5% cholic acid, and 20% sunflower oil were added and were given 3% alcoholic water for 60 days. Group III rats were fed with the same lipogenic diet and were treated with a dose of 250 μg/kg body weight CrCI₃·6H₂O and 100 mg/kg body weight niacin, for 45 days, by gavage. The rats in group IV were fed with pellet chow and treated with 250 μg/kg body weight CrCI₃·6H₂O and 100 mg/kg body weight niacin, by gavage, for 45 days. After 2 weeks, the animals showed symptoms of hyperlipemia. On the 60th day, tissue and blood samples were taken. We have observed decreased CAT activity and GSH levels, increased LDH activity, cholesterol, total lipid, and LPO levels in hyperlipemic rats. Niacin and Cr administration to hyperlipemic rats increased tissue GSH levels and CAT activity and decreased tissue LPO levels and LDH activity, cholesterol, and total lipid levels compared with hyperlipemic rats. We conclude that the administration of a combination of niacin and chromium has a protective effect against oxidative damage to tongue, lens, and spleen tissues as a result of hyperlipemia.     

Effects of aminothiols in 2-acetylaminofluorene-treated rats. II. Glutathione cycle and liver cytosolic activities

Reduced glutathione, enzymes involved in its metabolism and other cytosolic activities were evaluated in liver preparations of Wistar rats fed with a diet supplemented with 2-acetylaminofluorene (0.05%) and/or with glutathione or N-acetyl-L-cysteine (0.1%). The treatment lasted 4 cycles, each composed of 3 weeks of special diet followed by 1 week of standard diet. The carcinogen produced a considerable increase in gamma-glutamyl transpeptidase in liver homogenates at cycles III and IV, with an irreversible trend which was not discontinued even during the weeks of standard diet. Moreover, generally from cycle I, 2-acetylaminofluorene stimulated several enzyme activities in the liver cytosol, such as glutathione S-transferase, glutathione reductase, glucose 6-phosphate dehydrogenase, NADH- and NADPH-dependent diaphorases. Administration of the two aminothiols to untreated rats resulted in a significant enhancement of glutathione peroxidase, glucose 6-phosphate dehydrogenase and diaphorases. In 2-acetylaminofluorene-treated rats, both thiols further stimulated glutathione S-transferase during the last treatment cycles and attenuated gamma-glutamyl transpeptidase activity, which however was not sufficient to thoroughly counteract the liver lesions due to the massive feeding of the carcinogen. Hepatocellular glutathione was enhanced during the last cycle of treatment with 2-acetylaminofluorene, and was further increased by co-administration of exogenous glutathione.     

Induction of rat liver microsomal and nuclear cytochrome P-450 by dietary 2-acetylaminofluorene and butylated hydroxytoluene

The influence of dietary 2-acetylaminofluorene (AAF) on the cytochrome P-450 content of rat liver microsomal and nuclear fractions was immunochemically probed with monoclonal and polyclonal antibodies to cytochromes P-450c and P-450d. Cytochrome P-450d but not P-450c was immunodetected in microsomes, nuclear envelopes, and nuclei from untreated rats. The levels of both cytochromes P-450c and P-450d were elevated after a diet of either 0.1% AAF for 1 week or 0.05% AAF for 3 weeks. However, the level of cytochrome P-450c relative to P-450d was lower after the more prolonged AAF feeding. Supplementation of AAF-containing diets with 0.3% butylated hydroxytoluene (BHT), which affords protection against AAF hepatocarcinogenesis in high-fat fed rats, protected and/or induced total (spectral) nuclear envelope cytochrome P-450 content. Immunochemical studies of liver fractions showed that BHT enhanced the AAF-dependent induction of cytochrome P-450c, but not of P-450d. This was a concerted effect of AAF + BHT since dietary BHT by itself did not affect the levels of cytochrome P-450c or P-450d as compared to control rats. Since 1- to 3-week dietary AAF had little effect on total (spectral analyses) microsomal cytochrome P-450 but markedly reduced total P-450 in nuclear envelopes, the coordinated induction of specific cytochrome P-450s in the different fractions suggests selective induction and depression of different forms of cytochrome P-450 and provides additional evidence for independent regulation of the drug-metabolizing system in nuclear envelope and microsomes. In addition, these results suggest that regulation of cytochrome P-450 may play a crucial role in the nutritional modulation of AAF hepatocarcinogenesis.     

Identification and characterization of the glutathione and N-acetylcysteine conjugates of (E)-2-propyl-2,4-pentadienoic acid, a toxic metabolite of valproic acid, in rats and humans.

The severe hepatotoxicity of valproic acid (VPA) is believed to be mediated through reactive metabolites. The formation of glutathione (GSH) and N-acetylcysteine (NAC) adducts of reactive intermediates derived from VPA and two of its metabolites, 2-propyl-4-pentenoic acid (4-ene-) and 2-propyl-2,4-pentadienoic acid [(E)-2,4-diene VPA], was investigated in the rat. Rats were dosed ip with 100 mg/kg of VPA, 4-ene-, or 2,4-diene-VPA, and methylated bile and urine extracts were analyzed by LC/MS/MS and GC/MS, respectively. The GSH conjugate of (E)-2,4-diene VPA was detected in the bile of rats treated with 4-ene- and (E)-2,4-diene VPA. The NAC conjugate was a major urinary metabolite of rats given (E)-2,4-diene VPA and was a prominent urinary metabolite of those animals given 4-ene VPA. The NAC conjugate was also found to be a metabolite of VPA in patients. Both the GSH and NAC adducts were chemically synthesized and their structures established to be 5-(glutathion-S-yl)3-ene VPA and 5-(N-acetylcystein-S-yl)3-ene VPA by NMR and mass spectrometry. In contrast to the very slow reaction of the free acid of (E)-2,4-diene VPA with GSH, the methyl ester reacted rapidly with GSH to yield the adduct. In vivo it appears the diene forms an intermediate with enhanced electrophilic reactivity to GSH as indicated by the facile reaction of the diene with GSH in vivo [about 40% of the (E)-2,4-diene VPA administered to rats was excreted as the NAC conjugate in 24 hr]. The characterization of the GSH and NAC (in humans and rats) conjugates of (E)-2,4-diene VPA suggests that VPA is metabolized to a chemically reactive intermediate that may contribute to the hepatotoxicity of the drug.     

Prevention and therapy of squamous cell carcinoma of the rodent esophagus using freeze-dried black raspberries

Aim： This study was conducted to determine if short-term treatment of Nnitrosomethylbenzylamine （NMBA）-induced tumors in the rat esophagus with dietary freeze-dried black raspberries （FBR） would result in tumor regression and enhanced survival of the animals. Methods： Four-week-old male Fisher-344 rats were administered an AIN-76A control diet and injected subcutaneously with 0.5 mg/kg NMBA once per week for 15 weeks. At 19 weeks, when rats had an average of 5-6 tumors （papillomas） per esophagus, they were given a control diet containing either 5%, 10%, or 20% FBR. After 7 weeks of berry treatment, all surviving rats were killed and tumor incidence, number and volume were determined. Results： Esophageal tumor incidences, numbers and volumes in NMBA-treated rats were not influenced by any of the berry treatments. There were progressive increases in the survival of NMBA-treated rats fed 5%-20% FBR diets; however, these increases were not significant. Conclusion： FBR at 5%, 10%, and 20% of the diet had no effect on the development of NMBA-induced tumors in the rat esophagus or on animal survival when administered for 7 weeks beginning at the papilloma stage of tumor development. Thus, FBR appear to have no therapeutic value in the treatment of esophageal tumors. In contrast, dietary FBR are highly effective in preventing the development of NMBA-induced esophageal tumors in rats when administered before and during NMBA treatment or shortly after NMBA treatment when the esophagi contain preneoplastic （dysplastic） lesions of varying degrees of severity.     

Effect of urinary pH on the progression of urinary bladder tumours

Systemic alkalosis has been postulated to enhance tumorigenesis, whereas systemic acidosis has been implicated to exert a favourable influence on tumour control and regression. In the present study the urinary pH was influenced by feeding acid-forming or base-forming diets, and the effect of alkaline or acid urine on the early and late progression phase of urinary bladder carcinogenicity was investigated in male Wistar rats. Bladder lesions were initiated by N-butyl-N-(4-hydroxybutyl) nitrosamine (0.05% BBN in the drinking water during 4 weeks) and promoted by sodium bicarbonate (3.4% NaHCO₃ in the diet during 15 or 25 weeks). After short- (15 week) and more long-term (25 week) promotion with NaHCO₃, groups of 20 rats were fed a diet containing the acidifying salt ammoniumchloride (2.1% NH₄Cl) or the control diet. All surviving rats were killed after a total study duration of 52 weeks. Additional control groups were, after initiation, fed diets containing NaHCO₃ and killed after 15 wk or 25 wk of promotion, or at the end of the study. In rats fed diets with added salts, water intake and the amount of urine produced were increased and the urinary density was decreased compared to rats fed control diet. During NaHCO₃ feeding, urinary pH and sodium concentration were increased. During NH₄Cl feeding, urinary pH was decreased and urinary chloride and calcium concentrations were increased. Initiation by BBN followed by treatment with NaHCO₃ caused a high incidence of papillary/nodular hyperplasia, papillomas and carcinomas of the bladder epithelium. These lesions progressed with time or longer duration of NaHCO₃ promotion. A tumour protective effect of urinary acidification by NH₄Cl was not found. In fact, both acidification and prolonged alkalinization tended to aggravate the malignancy of bladder carcinomas.     

N-acetylcysteine (NAC) diminishes the severity of PCB 126-induced fatty liver in male rodents

Potent aryl hydrocarbon receptor agonists like PCB 126 (3,3',4,4',5-pentachlorobiphenyl) cause oxidative stress and liver pathology, including fatty liver. Our question was whether dietary supplementation with N-acetylcysteine (NAC), an antioxidant, can prevent these adverse changes. Male Sprague-Dawley rats were fed a standard AIN-93G diet (sufficient in cysteine) or a modified diet supplemented with 1.0% NAC. After one week, rats on each diet were exposed to 0, 1, or 5μmol/kg body weight PCB 126 by i.p. injection (6 rats per group) and euthanized two weeks later. PCB-treatment caused a dose-dependent reduction in growth, feed consumption, relative thymus weight, total glutathione and glutathione disulfide (GSSG), while relative liver weight, glutathione transferase activity and hepatic lipid content were dose-dependently increased with PCB dose. Histologic examination of liver tissue showed PCB 126-induced hepatocellular steatosis with dose dependent increase in lipid deposition and distribution. Dietary NAC resulted in a reduction in hepatocellular lipid in both PCB groups. This effect was confirmed by gravimetric analysis of extracted lipids. Expression of CD36, a scavenger receptor involved in regulating hepatic fatty acid uptake, was reduced with high dose PCB treatment but unaltered in PCB-treated rats on NAC-supplemented diet. These results demonstrate that NAC has a protective effect against hepatic lipid accumulation in rats exposed to PCB 126. The mechanism of this protective effect appears to be independent of NAC as a source of cysteine/precursor of glutathione.     

Flax seed oil and flax seed meal reduce the formation of aberrant crypt foci (ACF) in azoxymethane-induced colon cancer in Fisher 344 male rats.

Flax seed oil and flax seed meal are good sources of omega-3 fatty acids. The objective of this study was to explicate the effects of feeding flax seed oil and flax seed meal on AOM-induced aberrant crypt foci (ACF) in Fisher 344 male rats. Following an acclimatization period, rats were divided into six groups and fed AIN 93G diet Control (C), C+7 and 14% soybean oil (SBO), C+7 and 14% flax seed oil (FSO) and C+10 and 20% flax seed meal (FSM). All rats received 16 mg/kg body weight of AOM at 7 and 8 weeks of age. The rats were euthanized with CO2 at 17 weeks of age. FSM and FSO reduced the incidence of ACF which are putative precursor lesions in the development of colon cancer in the distal colon by 88% and 77%, in the proximal colon by 86% and 87% with a total reduction of 87.5% and 84%, respectively. Glutathione-S-transferase (GST) activities were significantly (P<0.05) higher in rats fed C+7 and 14% FSO and C+10 and 20% FSM, as compared to rats fed C+SBO diets. Results of this study showed that FSO and FSM reduced the incidence of AOM-induced ACF formation and may therefore be effective chemopreventive agents.     

Açai (Euterpe oleracea Mart.) feeding attenuates dimethylhydrazine-induced rat colon carcinogenesis

This study investigated the protective effect of spray-dried açaí powder (AP) intake on colon carcinogenesis induced by 1,2-dimethylhydrazine (DMH) in male Wistar rats. After 4 weeks of DMH administrations, the groups were fed with standard diet, a diet containing 2.5% or 5.0% AP or a diet containing 0.2% N-acetylcysteine (NAC) for 10 weeks, using aberrant crypt foci (ACF) as the endpoint. Additionally, two groups were fed with standard diet or a diet containing 5.0% AP for 20 weeks, using colon tumors as the endpoint. In ACF assay, a reduction in the number of aberrant crypts (ACs) and ACF (1–3 AC) were observed in the groups fed with 5.0% AP (37% AC and 47% ACF inhibition, p = 0.036) and 0.2% NAC (39% AC and 41% ACF inhibition, p = 0.042). In tumor assay, a reduction in the number of invasive tumors (p < 0.005) and tumor multiplicity (p = 0.001) was observed in the group fed with 5.0% AP. Also, a reduction in tumor Ki-67 cell proliferation (p = 0.003) and net growth index (p = 0.001) was observed in the group fed with 5.0% AP. Therefore the findings of this study indicate that AP feeding may reduce the development of chemically-induced rat colon carcinogenesis.     

Effect of dietary fiber on mammary tumorigenesis, estrogen metabolism, and lipid excretion in female rats.

We previously reported that supplementary dietary wheat bran significantly reduced the incidence of N-nitrosomethylurea (NMU) induced mammary tumors in rats fed a high fat (HF) diet and reduced to a lesser extent the incidence in rats fed a low fat (LF) diet compared to their unsupplemented controls. Using the same cohort of experimental animals, we here report the results of biochemical analyses designed to investigate the effect of supplemental dietary fiber on estrogen metabolism and lipid excretion. Serum, hepatic tissue, urine, and feces were obtained from rats which had been fed a HF (23.5% corn oil) diet, a HF plus fiber (HF + F, 10% soft white wheat bran, SWWB) diet, a LF (5.0% corn oil) diet, or a LF plus fiber (LF + F) diet for 15 weeks beginning 3 days after a single dose of NMU. Our working hypotheses to explain how dietary fiber protects against mammary tumorigenesis were that fiber may: 1) act as an antiestrogen; 2) decrease circulating estrogens; 3) alter the enterohepatic recirculation of estrogens; and 4) physically bind to lipid and remove it in the feces. Therefore, various indices of estrogen metabolism were assessed including: 1) circulating estradiol (E2) and progesterone; 2) hepatic estrogen receptor (ER) protein; 3) excretion of estrogen in the urine and feces; 4) the in vitro estrogen binding properties of SWWB; 5) fecal lipid content; and 6) the in vitro lipid binding capacity of SWWB. Serum 17 beta-estradiol and progesterone remained unchanged as did hepatic cytosolic (cER) and nuclear (nER) estrogen receptor protein content, in the fiber supplemented groups compared to their respective controls.(ABSTRACT TRUNCATED AT 250 WORDS)     

应用大鼠中期肝癌试验研究DEN和2-AFF的促癌作用

目的　应用大鼠中期肝癌试验研究二乙基亚硝胺(DEN)和 2 乙酰氨基芴 (2 AAF)的促癌作用。方法　♂SD大鼠单次ip 2 0 0mg·kg-1DEN启动 ,2wk后每天在饮水中加入 10、33、10 0 ppmDEN ,或以 2 2、6 6、 2 2mg·kg-12 AAF灌胃 ,连续 6wk。第 3周全部大鼠切除 2 /3肝 (partialhepatectomy) ,第 8周末处死 ,以免疫组化方法检测肝脏胎盘型谷胱甘肽S 转移酶 (GST P) ,以GST P阳性灶数量 /面积相对于仅DEN启动的对照组的增加 ,评价化合物的致癌性。结果　DEN和 2 AAF均引起肝GST P阳性灶数量和面积增加 ,并且显示剂量效应关系。结论　DEN和 2 AAF均具有促癌作用 ,大鼠中期肝癌试验是研究受试物促癌作用的简便、经济、有效的方法。     

Suppressive effect of irsogladine maleate on N-methyl-N-nitro-N-nitrosoguanidine (MNNG)-initiated and glyoxal-promoted gastric carcinogenesis in rats

The modifying effect of irsogladine maleate (IRG) on N-methyl-N-nitro-N-nitrosoguanidine (MNNG)-initiated and glyoxal-promoted gastric carcinogenesis was examined in male Wistar rats. Six-week-old rats were divided into ten groups. Groups 1 through 6 were given MNNG (100 mg/l in drinking water) for 25 weeks from the start of the experiment, whereas groups 7 through 10 received distilled water in the initiation phase as the vehicle treatment. Groups 1 and 8 were kept on the basal diet and distilled water throughout the experiment (55 weeks). Groups 2-8 were given 0.5% glyoxal in the drinking water for 30 weeks from 26th week of the experiment. Group 3 was fed the diet mixed with 100 ppm IRG for 25 weeks from the start of experiment. Groups 4 and 8 were fed the diet mixed with 100 ppm IRG for 30 weeks from 26th week of experiment. Groups 5 and 9 or 6 were given 100 or 25 ppm IRG containing diet, respectively throughout the experiment. Group 10 was given the basal diet and distilled water as the vehicle treated control. Tumors of upper digestive tracts (stomach and duodenum) were developed in groups: 1 (12/17 rats, 71%), 2 (11/12 rats, 92%), 3 (9/16 rats, 56%), 4 (5/12 rats, 42%), 5 (6/15 rats, 40%) and 6 (7/12 rats, 58%). High dose of IRG in initiation and/or promotion phase significantly reduced the incidence of tumors of the upper digestive tracts. The average numbers of the digestive tracts neoplasms in groups 3,5 and 6 given glyoxal and IRG were less than those in group 2 which received only glyoxal. These results suggest that IRG could be a preventive agent against the occurrence of neoplasms of the upper digestive tract.     

葡萄籽原花青素对2型糖尿病大鼠血清中SOD GSH MDA及NO表达的影响

目的观察葡萄籽原花青素(GSPE)对2型糖尿病大鼠血清中超氧化物歧化酶(SOD)、还原型谷胱甘肽(GSH)、丙二醛(MDA)及一氧化氮(NO)表达的影响。方法选取SPF级雄性SD大鼠30只,出生180d,体质量180～220g,高脂饲料喂养4周后再小剂量腹腔注射链脲佐菌素(STZ)诱导2型糖尿病模型,随机分为糖尿病对照组,GSPE250mg·kg-1·d-1、50mg·kg-1·d-1剂量干预组;另设6只为普食对照组。检测各组喂养第6周、10周后的血糖水平,并检测第10周后大鼠血清中SOD、MDA、GSH及NO的变化。结果GSPE能降低血糖,但效果不明显。在抗氧化指标的检测中,与糖尿病对照组相比,GSPE250mg·kg-1·d-1剂量干预组SOD、GSH明显升高(P<0.05),MDA、NO明显降低(P<0.05);50mg·kg-1·d-1剂量干预组SOD、GSH有所升高,MDA、NO有所降低,但差异无统计学意义(P>0.05)。结论较高剂量的GSPE能有效改善2型糖尿病大鼠的抗氧化能力,对其作用机制的进一步研究,可为GSPE对糖尿病及其并发症的营养干预治疗提供新的思路和依据。     

Lack of chemopreventive effects of ginger on colon carcinogenesis induced by 1,2-dimethylhydrazine in rats.

Ginger (Zingiber officinale Roscoe) has been proposed as a promising candidate for cancer prevention. Its modifying potential on the process of colon carcinogenesis induced by 1,2-dimethylhydrazine (DMH) was investigated in male Wistar rats using the aberrant crypt foci (ACF) assay. Five groups were studied: Groups 1-3 were given four s.c. injections of DMH (40 mg/kg b.w.) twice a week, during two weeks, whereas Groups 4 and 5 received similar injections of EDTA solution (DMH vehicle). After DMH-initiation, the animals were fed a ginger extract mixed in the basal diet at 0.5% (Group 2) and 1.0% (Groups 3 and 4) for 10 weeks. All rats were killed after 12 weeks and the colons were analyzed for ACF formation and crypt multiplicity. The rates of cell proliferation and apoptosis were also evaluated in epithelial colonic crypt cells. Dietary consumption of ginger at both dose levels did not induce any toxicity in the rats, but ginger meal at 1% decreased significantly serum cholesterol levels (p<0.038). Treatment with ginger did not suppress ACF formation or the number of crypts per ACF in the DMH-treated group. Dietary ginger did not significantly change the proliferative or apoptosis indexes of the colonic crypt cells induced by DMH. Thus, the present results did not confirm a chemopreventive activity of ginger on colon carcinogenesis as analyzed by the ACF bioassay and by the growth kinetics of the colonic mucosa.     

Influence of Nauclea latifolia. Leaf Extracts on Some Hepatic Enzymes of Rats Fed on Coconut Oil and Non-Coconut Oil Meals

Abstract

This work focuses primarily on the comparative response of rat liver enzymes to oral administration of the water-soluble fraction of 95% ethanol extract of Nauclea latifolia. Sm. (Rubiaceae) leaves with 10% coconut oil meal and normal rat chow fed for 8 weeks. Forty-eight mature male albino rats of the Wistar strain weighing between 200 and 230 g were divided into two experimental groups. In experiment 1, group 1 (n = 6) was fed normal rat chow for 8 weeks, and groups 2, 3, and 4 (n = 6) were on normal rat chow for 8 weeks before treatment with 170, 340, and 510 mg/kg body weight, respectively, of oral dose of the water-soluble fraction of the ethanol extract of N. latifolia. leaves. In experiment 2, group 1 (n = 6) was fed the 10% coconut oil meal as the experimental control, and groups 2, 3, and 4 (n = 6) were fed the 10% coconut oil meal for 8 weeks before commencing treatment for 2 weeks with the extract of N. latifolia. leaves. The effects of the N. latifolia. leaf extract on some marker enzymes were analyzed. There was a significant increase (p < 0.05) of aspartate aminotransferase (AST) activity in all the groups when compared to the control, but the increase was higher in the 10% coconut oil meal fed groups. Alanine aminotransferase (ALT) activity decreased significantly (p > 0.05) in experiment 1 animals when compared with control. Increase in ALT activity was however observed in experiment 2 (p < 0.05). Alkaline phosphatase (ALP) and lactate dehydrogenase (LDH) activities did not change in both experiments. There was no significant (p > 0.05) change in γ-GT activity in experiment 1, but in experiment 2 glutamyl transferase (GGT) decreased in the water-soluble fraction of the ethanol extract. N. latifolia. leaf extract is capable of reducing the activity of γ-GT if raised by other factors. We also concluded that feeding animals with 10% coconut oil meal predisposes them to more adverse effects by the extract of N. latifolia. leaves.     

Impact of high flaxseed diet on mitogen-induced proliferation, IL-2 production, cell subsets and fatty acid composition of spleen cells from pregnant and F1 generation Sprague-Dawley rats.

Flaxseed (FS) being rich in alpha-linolenic acid may alter the immune parameters. Therefore, we assessed the impact of FS and defatted flaxseed meal (FLM) on fatty acid composition, cell subsets, proliferation and IL-2 production by splenic lymphocytes. Pregnant female Sprague-Dawley rats were fed diets containing 0% FS and FLM, 20 or 40% FS, 13 or 26% FLM during gestation or gestation, lactation and 8 week post-weaning period. FS and FLM resulted in up to 8.3 fold and 4.6 fold increase in splenic ALA among pregnant rats, 4.5 fold and 1.2 fold increase in splenic ALA among F(1) generation rats. Splenic linoleic acid (LA) and arachidonic acid (AA) were 18 and 40% lower in 40% FS fed pregnant rats, and AA was 15% lower in all the other groups. Among F(1) rats, splenic LA and AA were 16 and 48% lower in 40% FS group, and AA was 18% lower in 20% FS and 26% FLM groups. Concanavalin A and phytohemagglutinin mediated proliferation of spleen cells were 60 and 52% lower in 40% FS fed pregnant and F(1) generation rats, respectively. No significant changes were observed in the cell subsets or IL-2 production by splenic cells from different groups.