Prevention of inhibitory effects of alpha-difluoromethylornithine on rat urinary bladder carcinogenesis by exogenous putrescine

We previously demonstrated that repeated instillation of alpha-difluoromethylornithine (DFMO), an irreversible inhibitor of ornithine decarboxylase (ODC), inhibits (or retards) urinary bladder carcinogenesis in rats. Since ODC catalyzes the first step in polyamine synthesis, the inhibition of polyamine formation may be responsible for tumor inhibition by DFMO. The present experiment was conducted using male Fischer rats with a heterotopically transplanted urinary bladder (HTB) to determine whether the effects of DFMO are prevented by exogeneous Pu. HTBs were treated with 0.25 mg of N-methyl-N-nitrosourea (MNU) once a week for 3 weeks and the animals were then arbitrarily divided into 6 groups. Beginning one week following the last MNU treatment, all rats received twice a week instillation (0.5 ml each) as follows: Group 1 rats, normal rat urine; Group 2, 2% DFMO in urine; Group 3, 250 microM Pu and 2% DFMO in urine; Group 4, 250 microM Pu in urine; Group 5, urine for 10 weeks followed by 2% DFMO in urine; and Group 6, urine for 10 weeks followed by 250 microM Pu and 2% DFMO in urine. At 10 weeks following the last MNU instillation 5 rats from each of Groups 1 through 4 were killed for determination of urothelial polyamine levels. An additional 4 rats of Group 1 were killed at 10 weeks for histological examination. All remaining rats were killed 20 weeks after the last MNU instillation. Polyamine levels showed no significant difference among the 4 groups. The incidence of carcinoma was significantly lower in the group treated with DFMO (p less than 0.001, Group 1 vs Group 2), confirming our previous observation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Combined astaxanthin and fish oil supplementation improves glutathione-based redox balance in rat plasma and neutrophils

The present study aimed to investigate the effects of daily (45 days) intake of fish oil (FO; 10mg EPA/kg body weight (BW) and 7 mg DHA/kg BW) and/or natural ASTA (1mg ASTA/kg BW) on oxidative stress and functional indexes of neutrophils isolated from Wistar rats by monitoring superoxide (O(2)(-)), hydrogen peroxide (H(2)O(2)), and nitric oxide (NO()) production compared to the progression of auto-induced lipid peroxidation and Ca(2+) release in activated neutrophils. Furthermore, phagocytic capacity, antioxidant enzyme activities, glutathione-recycling system, and biomarkers of lipid and protein oxidation in neutrophils were compared to the redox status. Our results show evidence of the beneficial effects of FO+ASTA supplementation for immune competence based on the redox balance in plasma (significant increase in GSH-dependent reducing power), non-activated neutrophils (increased activity of the glutathione-recycling enzymes GPx and GR) and PMA-activated neutrophils (lower O(2)(-), H(2)O(2), and NO() generation, reduced membrane oxidation, but higher phagocytic activity). Combined application of ASTA and FO promoted hypolipidemic/hypocholesterolemic effects in plasma and resulted in increased phagocytic activity of activated neutrophils when compared with ASTA or FO applied alone. In PMA-activated neutrophils, ASTA was superior to FO in exerting antioxidant effects. The bulk of data reinforces the hypothesis that habitual consumption of marine fish (e.g. salmon, which is a natural source of both astaxanthin and fish oil) is beneficial to human health, in particular by improving immune response and lowering the risk of vascular and infectious diseases.     

Mammary cancer promotion by ovarian hormones involves IGFR/AKT/mTOR signaling

In a previous study, we observed that N-methyl-N-nitrosourea (MNU)-induced mammary lesions are promoted to overt mammary cancers by exogenous administration of estradiol (E) and progesterone (P). The purpose of the present study was to identify the early molecular events occurring during the hormonal promotion of mammary carcinogenesis and persistent activation of molecular pathways responsible for tumor growth. Seven-week-old female Copenhagen (COP) rats, which are resistant to MNU-induced mammary carcinogenesis, were intraperitoneally administered a single dose of MNU (50 mg/kg body weight). Six weeks after carcinogen administration, the rats were treated with E+P, killed at 15th week and 43rd week to obtain mammary lesions and tumor tissues and the molecular analysis were performed. Quantitative RT-PCR experiments showed increased mRNA expression of Igfr, Grb2, Sos1, and Shc1 in mammary lesions and tumors. Immunoblot data also showed increased protein levels of IGFR, GRB2 and SHC1 in mammary lesions and tumors, which is in correlation with their respective RT-PCR data. Activation of AKT and ERK1/2 were up regulated in E+P treated mammary lesions and tumors. Molecular analysis of mTOR pathway proteins revealed increased phosphorylation of p70S6K and 4EBP1 in the hormone treated tumors indicating the activation of mTOR signaling. E+P treatment reduced the protein expression of BAX and increased BCL2 expression along with down regulation of active caspase 3 and 8. Together, these data demonstrate that ovarian hormones promote the lesions to mammary tumors by enhancing IGFR and Akt/mTOR signaling along with inhibition of apoptotic stimuli.     

Influence of hepatic cells on allogeneic islet transplantation in rats without immunosuppressive drugs.

With the hypothesis of a possible helpful effect of the liver on islets transplanted into it, we have performed experiments that suggest some effect of hepatic cells for islet tolerance. We have studied 6 groups of Wistar rats made diabetic with streptozotocin and transplanted in sham conditions and with a mixture of islets and hepatic cells (allo-co-transplantation) in several conditions, all of them via the portal vein, and observed them over 30 days. Groups were as follows: Group A had a sham transplantation with saline. Group B was transplanted with hepatic cells alone. Group C was transplanted with islets alone without hepatic cells. Group D was co-transplanted with cultured islets and fresh hepatic cells (ratio 1:100). Group E was as group D with a ratio of 1:200. Group F also had co-transplantation, but after co-culture of islets and hepatic cells for 24 hours. Results show reversion of diabetes in group D for 4-5 days, and thereafter, a fall of blood glucose during the period observed. The effect was less marked in group F after co-culture of islets and hepatic cells. Paradoxically, when the ratio of islets and hepatic cell were 1:200, the results were not so good. These results suggest that hepatic cells have some helpful effect on islets when co-transplanted in the liver via the portal vein. More studies are needed to clarify if this effect can be related to some hepatic cell subpopulation; also if the effect is a membrane one, cell-to-cell contact, or through some secreted product.     

The effect of 17β-estradiol treatment on the mass and the turnover of bone in ovariectomized rats taking a mild dose of thyroxin

We performed the dosing experiment to establish whether estrogen administration has any beneficial effects on the mass and the turnover of bone in ovariectomized rats taking a mild dose of thyroxin. Thirty-five Wistar rats, 28 weeks of age, received ovariectomies (OVX) or sham operations and were divided into five groups. Group I was the sham group, Groups 2–5 were ovariectomized. Group 2 was the OVX-control, Group 3 treated with thyroxin 30 μg/kg/day (T4), Group 4, 17β-estradiol 0.3 mg/kg/week (E2), and Group 5, the combination of T4 and E2. The duration of the experiment was 12 weeks. At the end of the experiment, serum chemistries were measured. Bone minerals in the femur were determined with single photon absorptiometry and bone turnover was assessed histomorphometrically. Alkaline-phosphatase increased in Group 3 (OVX-T4), but it reduced in Groups 4 (OVX-E2) and 5 (OVX-T4 + E2). Bone minerals decreased in Groups 2 (OVX) and 3. In Group 4, it was preserved at the same level as in Group 1. Group 5 showed a significant increase of bone mass compared with Group 1. Eroded surface and osteoid surface increased in Groups 2 and 3 and they were reduced in Groups 4 and 5. Bone volume and mineral apposition rate were at a maximum in Group 5. This study demonstrated that 17β-estradiol was capable of preventing the bone mass decrease by regulating the turnover in ovariectomized rats taking a mild dose of thyroxin. Osteoblast function appeared to be stimulated in combination with 17β-estradiol and thyroxin.     

The flavonoid chrysin attenuates colorectal pathological remodeling reducing the number and severity of pre-neoplastic lesions in rats exposed to the carcinogen 1,2-dimethylhydrazine

Phenolic compounds are naturally occurring, bioactive substances with marked antioxidant and anti-inflammatory potential. The flavonoid chrysin, found in high levels in honey bee propolis, inhibits the activity of enzymes involved in carcinogenesis. We have investigated the effect of chrysin on pre-neoplastic colorectal lesions (ACF, aberrant crypt foci) in a rat model of chemical carcinogenesis induced by 1,2-dimethylhydrazine (DMH). Female Wistar rats weighing 137.2?±?24.3 g received weekly one subcutaneous injection of DMH (20 mg/kg) for 10 weeks. The animals were divided into five groups each with seven animals: Group 1, 0.9% saline; Group 2, DMH+0.9% saline; Group 3, DMH+chrysin (10 mg/kg); Group 4, DMH+chrysin (100 mg/kg); Group 5, DMH+chrysin (200 mg/kg). Groups 2 and 3 showed a significant increase in ACF number, nucleolus organizer regions per enterocyte nucleus and nitrite/nitrate serum levels compared with Group 1. Groups 4 and 5 presented a significant reduction in all these parameters compared with Group 2. The levels of antioxidant minerals (copper, magnesium, selenium, zinc) and the number of enteroendocrine and mucin-producing cells were significantly reduced in Groups 2 and 3 but were similar in Groups 4 and 5 compared with Group 1. Chrysin, at 100 mg/kg and 200 mg/kg, was effective in attenuating pathological colorectal remodeling, reducing the number of pre-neoplastic lesions in rats exposed to DMH. Some of these effects might be attributable to the recovery of antioxidant mineral levels, a reduction in systemic nitrosative stress and an inhibition of the cellular proliferation induced by this flavonoid.     

Analysis of mammary tumors for cytochemical evidence of endogenous mammary peroxidase.

The purpose of this study was to determine whether or not endogenous mammary peroxidase can serve as a cytochemical marker to distinguish ovarian hormone-dependent from ovarian hormone independent mammary tumors. Spontaneous mammary tumors arising in virgin C3H and GR mice (hormone independent tumors) and hormone-dependent mammary tumors arising during pregnancy in GR mice were examined. None of these tumors contained mammary peroxidase. Mammary tumors induced in Sprague-Dawley rats with methylnitrousourea (MNU) and dimethylbenzanthracene (DMBA) were also examined. These tumors included hormone-dependent and hormone independent ones. Several of the DMBA-induced hormone-dependent tumors contained a few peroxidase-positive cells, but the hormone independent tumors were negative. All of the MNU-induced tumors examined were negative for mammary peroxidase. Twenty human breast tumors (malignant and non-malignant) removed from women at surgery, were also negative for mammary peroxidase. Our results indicate that endogenous mammary peroxidase cannot be used to distinguish hormone-dependent from hormone independent mammary tumors.     

Quantification of epithelial cell differentiation in mammary glands and carcinomas from DMBA- and MNU-exposed rats

Rat mammary carcinogenesis models have been used extensively to study breast cancer initiation, progression, prevention, and intervention. Nevertheless, quantitative molecular data on epithelial cell differentiation in mammary glands of untreated and carcinogen-exposed rats is limited. Here, we describe the characterization of rat mammary epithelial cells (RMECs) by multicolor flow cytometry using antibodies against cell surface proteins CD24, CD29, CD31, CD45, CD49f, CD61, Peanut Lectin, and Thy-1, intracellular proteins CK14, CK19, and FAK, along with phalloidin and Hoechst staining. We identified the luminal and basal/myoepithelial populations and actively dividing RMECs. In inbred rats susceptible to mammary carcinoma development, we quantified the changes in differentiation of the RMEC populations at 1, 2, and 4 weeks after exposure to mammary carcinogens DMBA and MNU. DMBA exposure did not alter the percentage of basal or luminal cells, but upregulated CD49f (Integrin α6) expression and increased cell cycle activity. MNU exposure resulted in a temporary disruption of the luminal/basal ratio and no CD49f upregulation. When comparing DMBA- or MNU-induced mammary carcinomas, the RMEC differentiation profiles are indistinguishable. The carcinomas compared with mammary glands from untreated rats, showed upregulation of CD29 (Integrin β1) and CD49f expression, increased FAK (focal adhesion kinase) activation especially in the CD29hi population, and decreased CD61 (Integrin β3) expression. This study provides quantitative insight into the protein expression phenotypes underlying RMEC differentiation. The results highlight distinct RMEC differentiation etiologies of DMBA and MNU exposure, while the resulting carcinomas have similar RMEC differentiation profiles. The methodology and data will enhance rat mammary carcinogenesis models in the study of the role of epithelial cell differentiation in breast cancer.     

Importance of sucking stimulation in lactation: ultrastructural aspects of mammary glands in the rat

The Authors refer the results of a study concerning the mammary glands of lactating rats. We made use of rats Wistar subdivided in three groups. Group A: each rat lactates 8 pups. Group B: each rat lactates 4 pups. 8 days before delivery we provided to hide the nipples of a half of breasts with sutures. Group C: They do not lactate. In the 6th day of suckling, after a period of intense suction, we removed the mammary glands. This material was processed for electronic microscopy. Morphological aspects obtained show a difference in development of cytoplasmatic organs specially manifest in R.E.R. and Golgian apparatus.     

The effects of desferrioxamine and quercetin on hepatic ischemia-reperfusion induced renal disturbance

BACKGROUND: The aim of this study was to analyze the effects of 45min of hepatic ischemia and 1h of reperfusion on renal oxidative stress parameters, on renal tissue damage, and the role of Desferrioxamin (Dfx) and Q on these parameters. METHODS: Thirty Wistar albino rats were randomized to five groups. Group I was the control group. Group II received no treatment. Groups III and IV received intramuscular injections of desferrioxamine (100mg/kg) and quercetin (50mg/kg), respectively. Group V was administered Dfx and quercetin in combination. After treatment for 3 days, groups II, III, IV, and V were exposed to total hepatic ischemia for 45min. Plasma alanine aminotransferase levels, renal malondialdehyde and reduced glutathione (GSH) activities were measured after reperfusion for 1h. Histopathological and ultrastructural analysis of renal tissues was carried out. RESULTS: Plasma creatinine and BUN levels were markedly increased in the IR group and pretreated groups. Kidney MDA increased in the IR group, Q and Dfx+Q significantly decreased kidney MDA Kidney GSH levels markedly decreased in the IR group, Dfx significantly increased kidney GSH. No evidence of overt injury was observed in any renal tissue under light and electron microscopy. CONCLUSIONS: Our data demonstrated that 45min of hepatic ischemia and 1h of reperfusion may alter renal functions and may cause oxidative stress on renal tissue. Q and Dfx seem to have a beneficial effect via the GSH system and modulation of MDA levels.     

The hydroalcoholic extract of watercress attenuates protein oxidation,oxidative stress,and liver damage after bile duct ligation in rats

Cholestatic liver disease is recognized by extreme collagen formation and deposition, which is mediated by free radicals. The aim of the current study was to investigate the probable hepatoprotective effects of hydroalcoholic extract of watercress (WC) against oxidative stress and liver injury in bile duct ligation (BDL)- induced cholestatic rats. A total of 32 male Wistar rats were divided into four groups; sham control (SC), BDL, SC + hydroalcoholic extract of WC and BDL + hydroalcoholic extract of WC. WC-treated rats received daily WC 500 mg/kg/day for 10 days. Biochemical tests, hepatic oxidative stress markers, and antioxidant enzymes activity were estimated. Further, liver hydroxyproline content was assayed and histological analysis was made. The BDL model markedly elevated the protein carbonyl (PCO) and hydroxyproline contents and decreased the glutathione peroxidase (GPx) activity. Hydroalcoholic extract of WC significantly decreased the surge in liver PCO and hydroxyproline levels and increased the reduced GPx enzyme activity contents in the hepatic tissue. As determined by hematoxylin and eosin staining, BDL considerably induced hepatocyte necrosis. Moreover, these changes were significantly attenuated by the hydroalcoholic extract of WC treatment. Our data indicate that the hydroalcoholic extract of WC extract attenuated liver damage in BDL rats by decreasing the hydroxyproline content and histopathological indexes. Also, it reduced oxidative stress by preventing the hepatic protein oxidation and enhancing the activity of the GPx enzyme via antioxidative effect and free-radical scavenging. Our findings suggest that hydroalcoholic extract of WC could be a beneficial new curative agent for cholestatic liver damage.     

Effect of acute swimming exercise on lactate levels and its relation with zinc in pinealectomized rats

It is argued that melatonin secreted from the pineal gland regulates the levels of zinc, which is an important trace element. Decreases in zinc levels of pinealectomized rats supports this relationship. There is an increasing amount of evidence suggesting that the pineal gland can have important effects on physical activity. The objective of the present study was to explore the changes in serum lactate levels in pinealectomized rats subjected to acute swimming exercise and its relation with zinc. Forty adult male rats of Spraque Dawley strain were equally allocated to four groups. Group 1: General Control Group. Group 2: Pinealectomized Control Group. Group 3: Swimming Control Group. Group 4: Pinealectomized Swimming Group. Serum zinc, melatonin and lactate levels were determined in the blood samples collected from the animals by a decapitation method. Zinc and melatonin levels were higher in Group 1 than in Groups 2, 3 and 4 (p < 0.01), higher in Group 3 than in Groups 2 and 4 (p < 0.01) and higher in Group 2 than in Group 4 (p < 0.01). The highest lactate levels were found in Group 4 (p < 0.01). Lactate levels in Group 3 were higher than those in Groups 1 and 2 (p < 0.01), while the levels in Groups 1 and 2 did not differ. Pinealectomy results in a significant increase in lactate levels in rats subjected to an acute swimming exercise. This increase in lactate levels may be associated with the decrease observed in zinc levels after pinealectomy.     

Serum IGF-1 levels correlate negatively to liver damage in diabetic rats

Abstract

Diabetes and insulin resistance frequently cause liver damage. Diabetes also causes reduction in liver and blood IGF-1 levels. We investigated the relation between liver damage and IGF-1 levels in diabetic rats. Fourteen Wistar albino rats were divided into control and diabetic groups. Diabetes was induced by streptozotocin. Rats were sacrificed for biochemical and histologic examinations 2 weeks after streptozotocin injection. Serum and liver IGF-1 levels were decreased, liver malondialdehyde (MDA) levels were increased, glutathione peroxidase (GPx) enzymes activities were decreased and serum alanine aminotransferase (ALT) levels were increased in diabetic group. Microscopic examination of liver revealed that normal tissue organization was disrupted in streptozotocin-induced diabetic rats. There was a strongly positive correlation between blood glucose levels and liver injury, and blood and liver IGF-1 levels. There was a strongly negative correlation between blood IGF-1 levels and hepatic injury. Our results suggest that reduction of blood IGF-1 levels correlates with hepatic injury and circulating IGF-1 levels may have predictive value for determining hepatic damage that results from diabetes. In addition, circulating IGF-1 levels are correlated with glutathione levels and the oxidative stress status of diabetic rat liver.     

Moderately high folic acid supplementation exacerbates experimentally induced liver fibrosis in rats

Under certain clinical circumstances, folic acid can have undesirable effects. We investigated the following: (i) the effects of moderately high folic acid supplementation on the course of liver impairment in CCl(4)-treated rats and (ii) the influence of folic acid supplements on the hepatic recovery following the interruption of the CCl(4)-induced toxic injury. Four experimental groups of rats were used: CCl(4)-treated rats (0.5 ml of CCl(4) twice a week i.p.) fed standard chow for up to 12 weeks (Group A); treated rats fed chow supplemented with 25 mg/kg folic acid from weeks 6 to 12 (Group B); treated rats fed a standard diet but with CCl(4) discontinued after 6 weeks to allow for tissue recovery over 4 weeks (Group C); rats as Group C but fed a diet supplemented with 25 mg/kg folic acid from weeks 6 to 10 (Group D). Liver and blood samples were obtained for biochemical, histological, and gene expression analyses. Animals that received the supplement had a higher content of collagen, activated stellate cells, and apoptotic parenchymal cells in biopsy tissue at weeks 8 and 10 of treatment and more extensive alterations in serum albumin and bilirubin concentrations (Group B vs. Group A). In some of the time periods analyzed, alterations were observed in the expression of genes related to apoptosis (B-cell leukemia/lymphoma 2, inhibitor of apoptosis 2) and to fibrosis (procollagen I, matrix metalloproteinase 7). In the recovery period (Groups C and D), folic acid administration was associated with increased hepatic inflammation and apoptosis and with a decrease in the tissue inhibitor of metalloproteinase-3 expression following 1 week of recovery. We conclude that folic acid administration aggravates the development of fibrosis in CCl(4)-treated rats. Follow-up studies are needed to determine whether folic acid treatment would be contraindicated in patients with chronic liver diseases.     

Postprandial Hypertriglyceridemia Predicts Development of Insulin Resistance Glucose Intolerance and Type 2 Diabetes

Insulin resistance (IR) and type 2 diabetes mellitus (T2DM) have been found to be associated with postprandial hypertriglyceridemia (PPHTg). However, whether PPHTg can cause IR and diabetes is not clear. We therefore investigated the role of PPHTg in development of T2DM in rat model of T2DM. 96 male Wistar rats were randomized into four groups (24 rats each). Control Group A, high sucrose diet (HSD) Group B, HSD+Pioglitazone (10mg/kg/day) Group C and HSD+Atorvastatin (20mg/kg/day) Group D. Fat and glucose tolerance tests were done at regular intervals in all groups besides insulin and body weight measurement. At 26 weeks, low dose streptozotocin (15mg/kg,i.p.) was given to half of the rats. All rats were followed up till 48 weeks. PPHTg developed as early as week 2 in Group B and stabilized by week 14. Group B displayed highest PPHTg compared to other groups. Atorvastatin treatment (Group D) abolished PPHTg which became comparable to controls, pioglitazone treatment partially blunted PPHTg resulting in intermediate PPHTg. Group B with highest PPHTg showed highest subsequent IR, glucose intolerance (GI) and highest incidence of prediabetes at week 26 and diabetes at week 34 and 46 compared to other groups. Group D rats displayed lower IR, GI, low incidence of prediabetes and diabetes at these time points compared to Groups B and C. ROC analysis showed that triglyceride area under the curve of each time point significantly predicts the risk of diabetes. Present study provides the evidence that PPHTg predicts the development of IR, GI and T2DM in rat model of diet induced T2DM.     

Reduction of 1-methyl-1-nitrosourea-induced mammary gland carcinoma by in vivo application of immunostimulatory CpG motifs in Sprague-Dawley rats

In the present work the role of 13-cis retinoic acid and CpG oligodeoxynucleotides (CpG-ODN) in a 1-methyl-1-nitrosourea (MNU)-induced mammary gland carcinoma animal model was investigated. Treatment with both components, applied either alone or in combination, induced a significant decrease of the tumour burden and the volume of tumours only in rats that received CpG-ODN (p = 0.046, compared to the MNU control group). The data indicate that the Th-1 biased immunostimulatory capacities of CpG motifs may play a significant role in induction of protective immune responses against mammary gland tumours in Sprague-Dawley rats.     

The modulatory influence of p-methoxycinnamic acid, an active rice bran phenolic acid, against 1,2-dimethylhydrazine-induced lipid peroxidation, antioxidant status and aberrant crypt foci in rat colon carcinogenesis

We investigated the chemopreventive effect of p-methoxycinnamic acid (p-MCA), an active phenolic acid of rice bran, turmeric, and Kaemperfia galanga against 1,2-dimethylhydrazine-induced rat colon carcinogenesis. Male albino Wistar rats were randomly divided into six groups. Group 1 consisted of control rats that received a modified pellet diet and 0.1% carboxymethyl cellulose. The rats in Group 2 received a modified pellet diet supplemented with p-MCA [80 mg/kg body weight (b.wt.) post-orally (p.o.)] everyday. The rats in Groups 3-6 received 1,2-dimethylhydrazine (DMH) (20 mg/kg b.wt.) via subcutaneous injections once a week for the first 4 weeks; additionally, the rats in Groups 4, 5 and 6 received p-MCA at doses of 20, 40 and 80 mg/kg b.wt./day p.o., respectively, everyday for 16 weeks. The rats were sacrificed at the end of the experimental period of 16 weeks. The DMH-treated rats exhibited an increased incidence of aberrant crypt foci (ACF) development; an increased crypt multiplicity; decreased concentrations of tissue lipid peroxidation markers such as thiobarbituric acid reactive substances (TBARS), conjugated dienes (CD) and lipid hydroperoxides (LOOH); decreased levels of tissue enzymic antioxidants such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR); and decreased levels of non-enzymic antioxidants such as reduced glutathione (GSH) and vitamins C, E and A in the colon. Supplementation with p-MCA significantly reversed these changes and significantly inhibited the formation of ACF and its multiplicity. Thus, our findings demonstrate that p-MCA exerts a strong chemopreventive activity against 1,2-dimethylhydrazine-induced colon carcinogenesis by virtue of its ability to prevent the alterations in DMH-induced circulatory and tissue oxidative stress and preneoplastic changes. p-MCA was more effective when administered at a dose of 40 mg/kg b.wt. than at the other two doses tested.     

Effect of dietary zinc intake on N-methyl-N-nitrosourea-induced mammary tumorigenesis in rats

Numerous studies have shown that zinc nutrition influences the growth of several types of tumor. However, the influence of zinc nutrition on mammary tumorigenesis is not known. To study the effects of dietary zinc intake on N-methyl-N-nitrosourea (MNU)-induced mammary tumorigenesis, female Sprague-Dawley rats were fed an egg-white-based diet providing 3 (Z3), 12 (Z12), or 31 (Z31) mg zinc/kg diet ad libitum. In addition, two pair-fed controls, PFZ12 and PFZ31, were also included. Fourteen weeks after MNU injection, cumulative tumor incidence and total number of tumors were lower in Z3 rats than in Z12 and Z31 rats. Cumulative tumor incidence and total number of tumors were lower in Z3 rats than in PFZ12 rats, but were the same as in PFZ31 rats. Cumulative tumor incidence and total number of tumors were also lower in pair-fed controls than in their corresponding ad libitum controls, but were the same between the ad libitum controls. Overall, the results showed that the effect of marginal zinc deficiency on MNU-induced mammary tumorigenesis in rats was primarily the result of a reduced feed intake associated with marginal zinc deficiency rather than zinc per se.     

Long-term hormonal promotion overcomes genetic resistance to mammary cancer

It is well known that ovarian steroids estradiol and progesterone play a vital role in the development of mammary cancer. Here, using the genetically highly resistant Copenhagen rats we demonstrate that sustained exogenous treatment with estradiol and progesterone overcomes genetic resistance to mammary cancer. It has been demonstrated that Copenhagen rats develop preneoplastic lesions upon exposure to carcinogens. However, these preneoplastic lesions fail to progress to ductal carcinomas in situ or overt mammary carcinomas. The preneoplastic lesions eventually decrease in number and are absent by 60 days post-carcinogen treatment. In the present study, we exposed 7-week-old female Copenhagen rats to N-methyl-N-nitrosourea (MNU; 50 mg/kg BW). Immediately after MNU treatment the rats were divided into the following groups: (1) control; (2) 30 mg estradiol 17β; (3) 30 mg progesterone; and (4) 30 mg estradiol 17β plus 30 mg progesterone. All hormone treatments were administered via individual silastic pellets for a period of 9 months post-carcinogen treatment. The control animals displayed a low incidence of mammary cancer (10%). Hormone treatments produced significantly higher incidences of mammary cancer, with estradiol at 50%, progesterone at 65% and estradiol plus progesterone at 90%. Hormone treatment sustained the growth of the lesions induced by MNU by increasing expression of Areg, Bcl-2, Ccnd-1 and Vegf genes, while decreasing expression of Bad, Bax, Casp 3, 8, 9 and p53 genes. Furthermore, hormone treatment increased CCND-1 and PARP proteins levels. The data clearly demonstrates that hormonal environment supports mammary cancer progression by increasing cell proliferation, and angiogenesis while inhibiting apoptosis.     

A comparative study on the protective effects of 17beta-estradiol, biochanin A and bisphenol A on mammary gland differentiation and tumorigenesis in rats

Mammary tissue differentiation and tumorigenesis were studied in female rats following subcutaneous injection at 2, 4 and 6 days after birth with low or high doses of 17beta-estradiol (0.1 or 10 microg; E2), biochanin A (0.1 or 10 mg; BCA) or bisphenol A (0.1 or 10.0 mg; BPA). Half of the rats were killed on day 35 to analyze the terminal end bud (TEB), terminal duct (TD) and alveolar bud (AB) of the mammary tissue. The remaining rats were injected, ip, with a dose of 50 mg/kg of N-nitroso-N-methylurea (MNU) at 7 weeks of age and sacrificed 26 weeks later. The incidence and multiplicity of mammary tumors (MT) decreased among all three different treated groups, dose-dependently. However, the pattern of mammary gland differentiation varied. No significant difference was observed after E2 administration. TEB decreased dose-dependently in BCA treated groups and the number of TD and AB were suppressed significantly in BPA high dose group.