Liver Of Young Rats Research Articles

Pentose phosphate pathway activity parallels lipogenesis but not antioxidant processes in rat liver.

The pentose phosphate pathway (PPP) is widely assumed to play a key role in both reductive biosynthesis and protection from oxidative stress because it is the major source of NADPH. However, little is known about the activity of the PPP in fatty liver, which is characterized by both oxidative stress and lipogenesis. This study was designed to test whether the PPP is active in parallel with lipogenesis and antioxidant processes in the fatty liver of whole animals. Eight- and 16-wk-old obese Zucker diabetic fatty rats and their lean littermates received [U-13C3]glycerol, and 13C labeling patterns of glucose and triglycerides were analyzed for the assessment of hepatic PPP activity and the potentially related processes simultaneously. Oxidative stress, antioxidant activity, and NADPH-producing enzymes in the liver were further examined. Both PPP activity and lipogenesis increased in the fatty liver of young obese Zucker rats but decreased together in older obese Zucker rats. As expected, lipid peroxidation measured by malondialdehyde increased in the fatty liver of obese Zucker rats at both ages. However, evidence for antioxidant processes such as [glutathione] or activities of glutathione reductase, glutathione peroxidase, and catalase was not altered. Hepatic PPP activity paralleled lipogenesis but was dissociated from biomarkers of oxidative stress or antioxidant processes. In summary, NADPH from the PPP was presumably consumed for reductive biosynthesis rather than antioxidant defense in the fatty liver.

Effects of a chronic l-arginine supplementation on the arginase pathway in aged rats

While ageing is frequently associated with l-arginine deficiency, clinical and experimental studies provided controversial data on the interest of a chronic l-arginine supplementation with beneficial, no or even deleterious effects. It was hypothesized that these discrepancies might relate to a deviation of l-arginine metabolism towards production of l-ornithine rather than nitric oxide as a result of age-induced increase in arginase activity. This study investigated the effect of ageing on arginase activity/expression in target tissues and determined whether l-arginine supplementation modulated the effect of ageing on arginase activity. Arginase activity and expression were measured in the heart, vessel, brain, lung, kidney and liver in young rats (3-months old) and aged Wistar rats (22–24-months-old) with or without l-arginine supplementation (2.25% in drinking water for 6weeks). Plasma levels of l-arginine and l-ornithine were quantified in order to calculate the plasma l-arginine/l-ornithine ratio, considered as a reflection of arginase activity. Cardiovascular parameters (blood pressure, heart rate) and aortic vascular reactivity were also studied. Ageing dramatically reduced plasma l-arginine and l-arginine/l-ornithine ratio, decreased liver and kidney arginase activities but did not change activities in other tissues. l-Arginine supplementation normalized plasma l-arginine and l-arginine/l-ornithine ratio, improved endothelial function and decreased systolic blood pressure. These effects were associated with decreased arginase activity in aorta along with no change in the other tissues except in the lung in which activity was increased. A strong mismatch was therefore observed between arginase activity and expression in analyzed tissues. The present study reveals that ageing selectively changes arginase activity in clearance tissues, but does not support a role of the arginase pathway in the potential deleterious effect of the l-arginine supplementation in aged patients. Moreover, our data argue against the use of the measurement of plasma l-arginine/l-ornithine ratio to estimate arginase activity in aged patients.

Higher specific activities of alkaline phosphatase and β-galactosidase for the cellular membrane integrity in young and old aged lithium treated rats

Background: Differentiate the specific activity of Alkaline phosphatase and β-galactosidase in LiCl2 treated young and old rat's brain and liver to their control. Material and Methods: Totally 4 groups male wistar rats (each n=5) are taken to assess the level of Alkaline phosphatase and β-galactosidase for 10 and 20 days LiCl2 treated young and old rat's brain and liver as compared to control. Results: LiCl2 increases protein content essentail for old brain cell activation. Among all four group rats Alkaline phosphatase and β-galactosidase showed increased specific activity for 10 and 20 days LiCl2 treated young and old rat's brain and liver as compared to their control. Infact Alkaline phosphatase showed significantly higher activity for 10 and 20 days LiCl2 treated young brain (16.77 ± 0.309 and 27.74 ± 0.237) than their control 3.80 ± 0.230 and old rat's brain (14.28 ± 0.215 and 16.30 ± 0.24) than their control 8.65 ± 0.304 nm/min/mg of protein, similarly higher activity obtained for young liver (19.51 ±0.487 and 21.28 ± 0.317) than their control 3.67 ± 0.402 and finally for the old liver (15.02 ± 0.355 and 18.45 ± 0.439) as compared to their control 3.26 ± 0.304 nm/min/mg of protein respectively. Conclusion: These results confirm both membrane bound enzymes showed higher specific activity for LiCl2 treatment in brain and liver cells. So lithium has positive effect on young and old brain cells for β-galactosidase and has more positive effect on Alkaline phosphatase for rat liver and brain for membrane integrity of cells. Keywords: Total protein, Alkaline phosphatase, β-galactosidase, Specific activity, Lithium Chloride

Chronic administration of methionine and/or methionine sulfoxide alters oxidative stress parameters and ALA-D activity in liver and kidney of young rats.

High levels of methionine (Met) and methionine sulfoxide (MetO) are found in several genetic abnormalities. Oxidative stress is involved in the pathophysiology of many inborn errors of metabolism. However, little is known about the role of oxidative damage in hepatic and renal changes in hypermethioninemia. We investigated the effect of chronic treatment with Met and/or MetO on oxidative stress parameters in liver and kidney, as lipid peroxidation (TBARS), total sulfhydryl content (SH), reactive oxygen species (ROS) and enzymes activities superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and delta aminolevulinic dehydratase (ALA-D). Serum biochemical parameters were evaluated. Wistar rats were treated daily with two subcutaneous injections of saline (control), Met (0.2-0.4g/kg), MetO (0.05-0.1g/kg) and the association between these (Met plus MetO) from the 6th to the 28thday of life. Our data demonstrated an increase of glucose and urea levels in all experimental groups. Cholesterol (MetO and Met plus MetO) were decreased and triglycerides (MetO) were increased. SOD (MetO and Met plus MetO) and CAT (Met, MetO and Met plus MetO) activities were decreased, while GPx was enhanced by MetO and Met plus MetO treatment in liver. In kidney, we observed a reduction of SH levels, SOD and CAT activities and an increase of TBARS levels in all experimental groups. ROS levels in kidney were increased in MetO and Met plus MetO groups. ALA-D activity was enhanced in liver (MetO and Met plus MetO) and kidney (Met plus MetO). These findings help to understand the pathophysiology of hepatic and renal alterations present in hypermethioninemia.

Long live the liver: immunohistochemical and stereological study of hepatocytes, liver sinusoidal endothelial cells, Kupffer cells and hepatic stellate cells of male and female rats throughout ageing.

Male/female differences in enzyme activity and gene expression in the liver are known to be attenuated with ageing. Nevertheless, the effect of ageing on liver structure and quantitative cell morphology remains unknown. Male and female Wistar rats aged 2, 6, 12 and 18months were examined by means of stereological techniques and immunohistochemical tagging of hepatocytes (HEP), liver sinusoidal endothelial cells (LSEC), Kupffer cells (KC) and hepatic stellate cells (HSC) in order to assess the total number and number per gram of these cells throughout life. The mean cell volume of HEP and HSC, the lobular position and the collagen content of the liver were also evaluated with stereological techniques. The number per gram of HSC was similar for both genders and was maintained throughout ageing. The mean volume of HSC was also conserved but differences in the cell body and lobular location were observed. Statistically significant gender differences in HEP were noted in young rats (females had smaller and more binucleated HEP) but were attenuated with ageing. The same occurred for KC and LSEC, since the higher number per gram in young females disappeared in older animals. Liver collagen increased with ageing but only in males. Thus, the numbers of these four cell types are related throughout ageing, with well-defined cell ratios. The shape and lobular position of HSC change with ageing in both males and females. Gender dimorphism in HEP, KC and LSEC of young rat liver disappears with ageing.

Evidence of oxidative stress in brain and liver of young rats submitted to experimental galactosemia.

Galactosemia is a disorder of galactose metabolism, leading to the accumulation of this carbohydrate. Galactosemic patients present brain and liver damage. For evaluated oxidative stress, 30-day-old males Wistar rats were divided into two groups: galactose group, that received a single injection of this carbohydrate (5μmol/g), and control group, that received saline 0.9% in the same conditions. One, twelve or twenty-four hours after the administration, animals were euthanized and cerebral cortex, cerebellum, and liver were isolated. After one hour, it was found a significant increase in TBA-RS levels, nitrate and nitrite and protein carbonyl contents in cerebral cortex, as well as protein carbonyl content in the cerebellum and in hepatic level of TBA-RS, and a significant decrease in nitrate and nitrite contents in cerebellum. TBA-RS levels were also found increased in all studied tissues, as well as nitrate and nitrite contents in cerebral cortex and cerebellum, that also present increased protein carbonyl content and impairments in the activity of antioxidant enzymes of rats euthanized at twelve hours. Finally, animals euthanized after twenty-four hours present an increase of TBA-RS levels in studied tissues, as well as the protein carbonyl content in cerebellum and liver. These animals also present an increased nitrate and nitrite content and impairment of antioxidant enzymes activities. Taken together, our data suggest that acute galactose administration impairs redox homeostasis in brain and liver of rats.

Study on IGF-1 and IGFBP-3 gene expression in liver of young rats with intermittent hypoxia

Objective:Using the model of young rats with intermittent hypoxia, to study the expression of insulin-like growth factor-1 (IGF-1) and insulin-like growth factor binding protein-3 (IGFBP-3) in liver, and to provide objective evidence for the possible existence of growth retardation in children with OSAHS. Method:Divided 24 rats randomly into three groups, as control group and the mild and severe hypoxia group. Normally fed control group, without treatment, the other two groups were kept in the cabin has been simulated mild and severe intermittent hypoxia conditions of OSAHS in children. 8-hour day cycle of intermittent hypoxia, a total of 35 days. To the last day, animals were sacrificed and fresh liver tissues were fixed in liquid nitrogen, stored in the -80°C refrigerator, then took the molecular biology experiment of IGF-1 and IGFBP-3 in the liver. Result:The expression of IGF-1 mRNA in liver, semi-quantitative analysis showed that the difference of mRNA expression of IGF-1 among the three groups was statistically significant (P<0.05), pairwise comparison, mild hypoxia group was higher than control and severe group, there were significant differences (P<0.05), the control group and severe hypoxia had no significant difference (P>0.05). The expression of IGFBP-3 mRNA in liver showed that, differences between the three groups was not significant (P>0.05). IGF-1 expression in liver tissue analysis showed that, differences between the three groups was statistically significant (P<0.05), pairwise comparisons, its expression in the control group was lower than mild hypoxia group and severe group, there were significant differences (P<0.05), mild hypoxia and severe hypoxia group had no significant difference (P>0.05). IGFBP-3 expression in liver tissue analysis showed that, differences between the three groups was statistically significant (P<0.05), pairwise comparisons, the control group was higher than mild and severe hypoxic group, there were significant differences (P<0.05), mild hypoxia and severe hypoxia group had no significant difference (P>0.05). Conclusion:IGF-1 and IGFBP-3 in the liver of mild hypoxia group, severe hypoxic group and control group showed that their transcription levels and the severity of hypoxia had no significant correlation.

Effects of Acute Administration of D,L-Homocysteine Thiolactone on the Antioxidative Status of Rat Intestine and Liver

Abstract Oxidative stress appears to play a role in the pathogenesis of several inflammatory gastrointestinal diseases. Increased homocysteine levels may play a role in the pathogenesis of Chron’s disease and ulcerative colitis. The aim of this study was to examine the influence of homocysteine on the antioxidant status of rat intestine and liver. The levels of thiobarbituric acid reactive substances (TBARS), activity of catalase (CAT) and total antioxidant status (TAS) were investigated in the isolated gut and liver of young male rats in the control group (8 rats) and after 3-hоur incubation in high doses of D, L-homocysteine thionolactone (Hcy) (10 μmol/L) (8 rats). Samples of duodenum, ileum, colon and liver were homogenized in sodium phosphate buffer (1:10). Homogenates were centrifuged at 10000 for 10 min at 4° C and the supernatant was taken for biochemical assays. Our results showed that high D, L-homocysteine thionolactone concentration reduced enzymatic catalase activity in homogenates of the isolated segments of duodenum (27.04%) p&lt;0.01; ileum (37.27%), colon (34.17%) and liver (67.46%) p&lt;0.001. Exposition to high D,L-homocysteine thiolactone concentration significantly increased TBARS levels in the duodenum (106.05%), ileum (47.24%), colon (112.75%) and liver (32.07%) (p&lt;0.01). Homocysteine also modifi ed the total antioxidant status of homogenates from the duodenum, ileum, colon and liver, increasing by 20.68% (duodenum), 24.74% (ileum), 14.88% (colon) and 19.35% (liver) (p&lt;0.001). Homocysteine induced a consistent oxidative stress in rat’s intestine and liver (reduced activity of catalase and increased level of TBARS), but the elevated activity of TAS in our experiments could be explained as an adaptive response to the generated free radicals which indicates the failure of the total antioxidant defense mechanism to protect the tissues from damage caused by homocysteine.

Ginger and alpha lipoic acid ameliorate age-related ultrastructural changes in rat liver

Because of the important role that oxidative stress is thought to play in the aging process, antioxidants could be candidates for preventing its related pathologies. We investigated the ameliorative effects of two antioxidant supplements, ginger and alpha lipoic acid (ALA), on hepatic ultrastructural alterations in old rats. Livers of young (4 months) and old (24 months) Wistar rats were studied using transmission electron microscopy. Livers of old rats showed sinusoidal collapse and congestion, endothelial thickening and defenestration, and inconsistent perisinusoidal extracellular matrix deposition. Aged hepatocytes were characterized by hypertrophy, cytoplasmic vacuolization and a significant increase in the volume densities of the nuclei, mitochondria and dense bodies. Lipofuscin accumulation and decreased microvilli in bile canaliculi and space of Disse also were observed. The adverse alterations were ameliorated significantly by both ginger and ALA supplementation; ALA was more effective than ginger. Ginger and ALA appear to be promising anti-aging agents based on their amelioration of ultrastructural alterations in livers of old rats.

Integrated Transcriptome and Proteome Analyses Reveal Organ-Specific Proteome Deterioration in Old Rats

SummaryAging is associated with the decline of protein, cell, and organ function. Here, we use an integrated approach to characterize gene expression, bulk translation, and cell biology in the brains and livers of young and old rats. We identify 468 differences in protein abundance between young and old animals. The majority are a consequence of altered translation output, that is, the combined effect of changes in transcript abundance and translation efficiency. In addition, we identify 130 proteins whose overall abundance remains unchanged but whose sub-cellular localization, phosphorylation state, or splice-form varies. While some protein-level differences appear to be a generic property of the rats’ chronological age, the majority are specific to one organ. These may be a consequence of the organ’s physiology or the chronological age of the cells within the tissue. Taken together, our study provides an initial view of the proteome at the molecular, sub-cellular, and organ level in young and old rats.

Prolonged rest period enables the detection of micronucleated hepatocytes in the liver of young adult rats after a single dose of diethylnitrosamine or mitomycin C

A repeated-dose micronucleus assay utilizing young adult rat hepatocytes was recently developed to evaluate the genotoxicity. In this assay, accumulation of micronucleated hepatocytes (MNHEPs) induced by repeated dosing of genotoxic chemicals is considered to be a key factor in the detection of micronuclei induction. Then, we hypothesized that the period following chemical exposure enable the detection of MNHEP induction in young adult rats, namely that MNHEPs can be generated from chromosomally damaged cells and accumulate following initiation of chemical exposure until sampling. We therefore measured MNHEP induction at 2 or 4 weeks after a single oral administration of 12.5, 50, or 100mg/kg of diethylnitrosamine (DEN) or an intraperitoneal administration of 0.5, 1.0, or 2.0mg/kg of mitomycin C (MMC) to young adult rats. Results showed a statistically significant, dose-dependent increase in the numbers of MNHEPs in DEN- or MMC-treated rats, indicating that prolonged rest period following a single dose of a genotoxic chemical enables the detection of MNHEP induction in the liver of young adult rats. From these results, a single oral administration of 50mg/kg of DEN with a 2- or 4- week rest period can be used as a positive control in repeated-dose liver micronucleus assays. This procedure is superior in terms of labor saving and animal welfare to repeated dosing of DEN.

Effects of buprenorphine on balance of oxidant/antioxidant system in the different ages of male rat liver.

Our knowledge about a link between buprenorphine and hepatotoxicity is controversial. This study evaluated the effects of buprenorphine on the liver of young, adult, and aged rats. For this reason, young, adult, and aged rats received intraperitoneally 0.25, 0.5, and 1 mg/kg buprenorphine for 30 days. The present results revealed that the normal aging was associated with a significant decrease in the activities of antioxidant enzymes, and an increase in the liver lipid peroxidation, serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), and lactate dehydrogenase (LDH) activities in the aged rats. This study also demonstrated that buprenorphine led to a significant increase in the serum activities of ALT, AST, and LDH as well as liver lipid peroxidation content with a decrease in the antioxidant enzymes in the liver of buprenorphine-treated aged rat versus the aged matched control animals. In conclusion, the present results demonstrate that buprenorphine deteriorated oxidative damage in the aged livers.

Repeated dose liver and gastrointestinal tract micronucleus assays using N-methyl-N′-nitro-N-nitrosoguanidine in young adult rats

N-Methyl-N′-nitro-N-nitrosoguanidine (MNNG) is a direct-acting mutagen that induces tumors in the glandular stomach, but not in the liver or colon, of rats after oral administration. To evaluate the performance of repeated dose liver and gastrointestinal tract micronucleus (MN) assays in young adult rats, MNNG was administered by oral gavage to male CD (SD) rats aged 6 weeks at doses of 0 (vehicle; 2.5% DMSO aqueous solution), 3.125, 6.25, 12.5, and 25mg/kg/day once daily for 14 and 28 days, and the MN frequencies were examined in the hepatocytes, glandular stomach cells, and colonic cells. The MN induction in immature erythrocytes in the bone marrow of these animals was also simultaneously evaluated. The frequencies of micronucleated (MNed) glandular stomach cells were significantly increased in all MNNG treatment groups in a dose-dependent manner in both repeated dose studies. In contrast, the frequencies of MNed hepatocytes and colonic cells were not significantly increased compared to the vehicle control. In the bone marrow, a small but significant increase in the frequency of MNed immature erythrocytes was observed only at the highest dose in the 28-day study. Since a clear positive result in the glandular stomach agrees with the tissue specificity of tumor induction by this chemical, the MN assay with the glandular stomach, which is a direct contact site with high concentrations of test substances administered by oral gavage, may be useful for detecting genotoxic compounds that are short-lived in vivo, such as MNNG.

Lithium Toxicity Effects on Oxidative Stress, Dyslipidemia and Apoptosis in the Aged Rats

Aging is associated with metabolic changes and the development of diseases, due to the reduction of antioxidant defenses and alteration in apoptosis process. The lithium is used to treat bipolar disorder and neuroprotector; it also can be used as an antioxidant, but its function in aging has not been elucidated. The alterations in apoptosis could be associated with development oxidative stress in several tissues, although this information is unclear to aged rats. Disorders in apoptosis process and/or oxidative stress development impair the health of aged rats. The association between apoptosis with hepatic metabolism changes and oxidative stress disorder in aging is also unclear. Therefore, the objective of this work was to determine the effects of lithium on the lipid profile in serum and oxidative stress as well as apoptosis in the liver of aged rats. Twenty female Wistar rats were divided into 4 groups (n=5): the C group, with 3- month-old rats that received only water; the L group, with 3- month-old rats that received a lithium solution in drinking water; the S group, with 22- month-old rats that received water; and the SL group, with 22- month-old rats that received lithium in drinking water. The total experimental period was 30 days. All animals received standard diet ad libitum. The lithium dose took was according to neuroprotective dose and carefully monitored daily. The dyslipidemia studies were made through TC, HDL, LDL, VLDL, TG and glucose in serum. Oxidative stress analyses involved experiments with LH, TAS and ATP-SA. The apoptotic proteins analyses were made by western blot. Oxidative stress and apoptotic proteins were studied in the liver rats. The results showed that the lithium treatment reduced energy intake, aqueous solution intake and palatability in both, young and aged rats. This treatment increased TG and VLDL in the serum of animals in both groups. The treatment promoted hyperglycemia in young group, and in aged group, induced LDL enhanced as well as decreased HDL. Lithium induced enhanced Sirt 1 in livers of young and aged rats. TAS were higher in young group submitted lithium treatment. The livers of aged rats supplemented with lithium exhibited raised ATP- SA and Bax. In conclusion, the lithium induced dyslipidemia and hyperglycemia in the young, but this treatment also acted as a possible antioxidant agent, associated with Sirt 1 enhanced to protect this tissue of damages. In the aged rats, lithium promoted dyslipidemia and could induce cell death. Therefore, the supplementation could exert toxic effects in the livers of aged rats.

Arsenic and nicotine co-exposure lead to some synergistic effects on oxidative stress and apoptotic markers in young rat blood, liver, kidneys and brain.

Arsenic and nicotine exposure has been a major health concern globally. Individually both these toxicants increase the risk to various diseases including cancers. However, limited information exists on the co-exposure. In this study, we evaluate the effects of their individual and combined exposure and if co-exposure to these toxicants might have a synergism or antagonism. Male rats were exposed to a very low dose of arsenic (25 ppm in drinking water) or nicotine (0.25 mg/kg, sub-cutaneously) for a period of 5 months and post exposure various biochemical variables indicative of oxidative stress and apoptosis evaluated. Almost all glutathione linked enzymes showed marked alteration in individual as well as co-exposure treated groups. While serum creatinine and apoptosis indicator, lactate dehydrogenase (LDH) were significantly increased in both treatments, an additive effect was noted in co-exposure group. A similar trend was also seen in brain and liver but not in kidneys. Gene expression studies showed marked reduction in catalase, Cu-Zn SOD, GST, there was a significant up regulation in Bax, caspase 3 in various tissues along with urinary 8-OHdG levels, indicative of DNA damage and apoptosis. Interestingly, a decrease in liver arsenic concentration was noted in co-exposed group compared to arsenic alone exposed group. In conclusion, the present study suggests that arsenic and nicotine exhibited significant toxicity during individual exposure whereas co-exposure to these toxins showed variable conditions (indicative of both synergism and antagonism) in male rats.

Micronucleus induction in rat liver and bone marrow by acute vs. repeat doses of the genotoxic hepatocarcinogen monocrotaline

The liver micronucleus (MN) assay is useful for predicting genotoxic rodent hepatocarcinogenicity. We have recently established the repeated-dose liver MN (RDLMN) assay in rats for integration into general toxicity studies. To investigate the effectiveness of the RDLMN assay, the genotoxic rodent hepatocarcinogen, monocrotaline (MCT), was administered by oral gavage to 6-week old male rats once daily for 14 days at 0.5 and 1.5mg/kg/day, and for 28 days at 0.15, 0.5, 1.5, 3.75, 7.5 and 15mg/kg/day. Then, MN induction was measured in the liver and bone marrow (BM), and histopathological hepatotoxicity was examined. Additionally, in order to evaluate the effects of repeated dosing periods on MN inducibility, a double-dose examination of MCT at doses of 15, 30 and 60mg/kg/day in juvenile (26-days old) and young adult (7-weeks old) rats was also conducted, as an acute dose MN assay. The peripheral blood (PB) and liver were sampled at 48h and 4 days after the second dosing, respectively. In the repeated-dose MN assay, MCT produced a positive result in the liver at a non-hepatotoxic lower dose level, but not in the BM at any dose level. In contrast, in the double-dose MN assay, MCT showed a negative result in the young adult rat livers, although it gave positive responses in the livers of juvenile rats and in the PB with both age groups. The maximum dose used in the repeated-dose assay was considerably lower than that used in the acute dose assay. These results suggest that a repeated dosing regimen is more suitable for the liver MN assay using young adult rats than an acute dose regimen, and the RDLMN assay might be capable of detecting genotoxic rodent hepatocarcinogens at dose levels that are typically undetectable in BM MN assays.

Evaluation of the repeated-dose liver micronucleus assay with p-dimethylaminoazobenzene

The micronucleus induction by p-dimethylaminoazobenzene (DAB), a genotoxic rat liver carcinogen, was assessed in the liver and bone marrow of young adult rats after the repeated administration of DAB for 14 (Lab. 1) and 28 (Lab. 2) days. Three dose levels, 25, 50 and 100mg/kg/day, were used for the investigations in both labs.The frequency of micronucleated hepatocytes was significantly increased in a dose-dependent manner after the repeated administration of DAB at 50mg/kg/day or more for 14 and 28 days. Similarly, the frequency of micronucleated immature erythrocytes in the bone marrow was increased after the repeated administration of DAB at 100mg/kg/day for 14 and 28 days.These results indicate that the repeated-dose liver micronucleus assay allowed for the detection of micronucleus induction by DAB, and that the lowest detectable dose for micronucleus induction in the liver was lower than in the bone marrow. Thus, the repeated-dose liver micronucleus assay using young adult rats is considered suitable for the detection of micronucleus induction by liver carcinogens, such as DAB.

Repeated-dose liver and gastrointestinal tract micronucleus assays with CI Solvent Yellow 14 (Sudan I) using young adult rats

The in vivo genotoxicity of CI Solvent Yellow 14 (Sudan I) was examined using repeated-dose liver and gastrointestinal tract micronucleus (MN) assays in young adult rats. Sudan I is a mono-azo dye based on aniline and 1-amino-2-hydroxynaphthalene. This dye was demonstrated as a rat liver carcinogen in a National Toxicology Program (NTP) bioassay, and genotoxicity was noted in a rat bone marrow micronucleus (BMMN) assay. In the present study, Sudan I was administered orally to rats for 14-days, and the MN frequency in the liver, stomach, colon, and bone marrow were analyzed. The frequency of micronucleated hepatocytes (MNHEPs) was not significantly increased by the administration of the Sudan I. Gastrointestinal tract MNs were also not induced. However, in the BMMN assay, a significant increase in micronucleated immature erythrocytes (MNIMEs) was observed in a dose-dependent manner. While Sudan I has been reported to lack hepatic genotoxicity, it has also exhibited tumor-promoting activities. These results are consistent with the lack of induction of MN in the hepatocytes. The lack of MN induction in cells of the gastrointestinal tract was also logical because azo-compounds are reported to be unlikely to induce DNA damage in the rat gut. The repeated-dose rat liver and gastrointestinal tract MN assays have the potential to be used in the evaluation of the genotoxicity of a chemical in each organ in accordance with its mode of action.

Glutathione metabolism enzymes in brain and liver of hyperphenylalaninemic rats and the effect of lipoic acid treatment

Phenylketonuria (PKU) is a disorder caused by a deficiency in phenylalanine hydroxylase activity, which converts phenylalanine (Phe) to tyrosine, leading to hyperphenylalaninemia (HPA) with accumulation of Phe in tissues of patients. The neuropathophysiology mechanism of disease remains unknown. However, recently the involvement of oxidative stress with decreased glutathione levels in PKU has been reported. Intracellular glutathione (GSH) levels may be maintained by the antioxidant action of lipoic acid (LA). The aim of this study was to evaluate the activity of the enzymes involved in the metabolism and function of GSH, such as glutathione peroxidase (GSH-Px), glucose-6-phosphate dehydrogenase (G6PD), glutathione reductase (GR), glutamate-cysteine ligase (GCL), glutathione-S-transferase (GST) and GSH content in brain and liver of young rats subjected to a chemically induced model of HPA and the effect of LA for a week. In brain, the administration of Phe reduced the activity of the GSH-Px, GR and G6PD and LA prevented these effects totally or partially. GCL activity was increased by HPA and was not affect by LA antioxidant treatment. GST activity did not differ between groups. GSH content was increased by LA and decreased by HPA treatment in brain samples. Considering the liver, all parameters analyzed were increased in studied HPA animals and LA was able to hinder some effects except for the GCL, GST enzymes and GSH content. These results suggested that HPA model alter the metabolism of GSH in rat brain and liver, which may have an important role in the maintenance of GSH function in PKU although liver is not a directly affected organ in this disease. So, an antioxidant therapy with LA may be useful in the treatment of oxidative stress in HPA.

Epigallocatechin-3-gallate restores the Bcl-2 expression in liver of young rats challenged with hypercholesterolemia but not in aged rats: an insight into its disparity of efficacy on advancing age

Advanced age significantly increases cholesterol levels, however, when combined with a high cholesterol diet it not only leads to life-threatening conditions like atherosclerosis, but also plays a central role in the pathogenesis of hepatic damage and its complications. Even though extensive studies have been carried out to elucidate the causative factors that lead to hepatic steatosis associated with liver damage in young rats due to hypercholesterolemia, events that occur in aged rats where a different milieu is presented by up and down regulation of various genes co-existing, has not been extensively studied. Hence, this study comparatively evaluates the impact of hypercholesterolemic stress induced liver damage in young and aged rats and the efficacy of epigallocatechin-3-gallate to protect the liver in both young and aged rats with special reference to apoptosis. Moreover, the work has been designed to investigate whether aged rats act as better models for studying the efficacy of atheroprotective drugs. Male albino rats of the Wistar strain were used in this study. Basic biochemical assays along with apoptotic markers assayed in the current study revealed that treatment with EGCG significantly reverted the alterations in both biochemical and histological parameters in young and aged hypercholesterolemic rats when compared to their respective controls. However, the extent of reversion was far superior in young rats, when compared to aged rats. EGCG reduced hepatic Bax expression in both young and aged hypercholesterolemic rats. On the other hand, Bcl-2 expression was up regulated significantly in young hypercholesterolemic rats, but not in aged hypercholesterolemic rats on treatment with EGCG. This throws light on the efficacy of the treatment differing in young and aged rats as well; atheroprotective drugs shall be tested for their efficacy in aged hypercholesterolemic models.