Effect of the co-administration of phenobarbital, quercetin and mancozeb on nitrosomethylurea-induced pancreatic tumors in rats

We have previously shown that a single i.p. injection of nitrosomethylurea (NMU) in 3-day-old rats orally treated with the pesticide mancozeb (MZ), the flavonoid quercetin (Q) or in combination (MZ-Q) induces hyperplasia, atypical acinar cell proliferation and carcinoma in situ (CIS) in the pancreas. This work studies the effect of oral administration of phenobarbital (PB) on this model of pancreatic carcinogenesis. The animals were fed on a diet supplemented by MZ or/and Q from the 10th day of pregnancy, thorough lactation and as pups after weaning until being sacrificed at week 24. Saline injection with non-supplemented diet was used for the control group (SAL). The experimental groups were (1) SAL (control), (2) SAL-PB, (3) NMU, (4) NMU-PB, (5) MZ-NMU, (6) MZ-NMU-PB, (7) Q-NMU, (8) Q-NMU-PB, (9) MZ-Q-NMU and (10) MZ-Q-NMU-PB. Acinar cell hyperplasia was found in all groups of NMU-treated rats. Dysplastic foci (DYS) were seen in groups 3-10 at the following percentages: 19, 48, 71, 27, 71, 35, 100 and 30, respectively. CIS were recorded in groups 4 to 10 at percentages: 4, 36, 13, 11, 0, 16, 5, respectively.

CONCLUSION

Although PB, Q or MZ given alone enhance DYS lesions in NMU-treated rats, the MZ/Q/PB combined treatments may increase (mainly in males) or decrease (mainly in female) the DYS and CIS proportion. Because PB, MZ and Q influence P450 enzymes, we suggest that these enzymes play a role in the carcinogenesis process.

Dietary lipids modulate fatty acid composition, gamma glutamyltranspeptidase and lipid peroxidation levels of the epididymis tissue in mice

The purpose of this work was to analyze the effect of diets that contain several oils whose composition in fatty acids were different, on the kinetic parameters of the gamma-glutamyltranspeptidase (GGTP) and the lipoperoxidation of the epididymis because GGTP controls the level of the glutathione that is an molecule that regulates the level of oxidation protecting the maturation and survival of sperm in the lumen of the epididymis. The caput portion of the epididymis was chosen because the epithelium of this segment synthesizes GGTP. Weaned BALB-c mice were fed a commercial or semi-synthetic diet that contained 5% added olein. The mice were maintained on corn oil or fish oil diet for the first 4-8 months of age. The kinetic variables of the GGTP enzyme, analyzed by means of multiple regression analysis using dummy variables, showed that values were similar in olein and corn oil samples, whereas in samples from the fish oil fed group the enzyme behaved as that in animals maintained on commercial diets. Although there were no variations in maximum velocity (Vm) of the enzyme, the Km value, was greater (P < 0.0001) for the mice fed the olein and corn diets. These groups contained greater percentages of the monounsaturated fatty acids, palmitoleic (16:1 n-7) and oleic acid, 18:1 n-9. Similarly, the amount of lipid peroxidation was also greater in the olein and corn oil groups with respect to commercial and fish groups. The significant increment in Km of GGTP in the olein and corn groups was correlated with greater amount of monounsaturated fatty acids and lipid peroxidation in the epididymis. In conclusion, modifications of dietary lipid sources differentially modulated the epididymis tissue fatty acid profile, lipid peroxidation amounts, and the Km of GGTP. These effects may alter the metabolism of the natural substrate of GGTP, glutathione, a tripeptide with a powerful antioxidant activity, which is necessary in maintaining the oxidative state of the sperm microenvironment, thereby favoring maturation of the male gametes.

Neoplastic and preneoplastic lesions induced by melamine in rat urothelium are modulated by dietary polyunsaturated fatty acids

The modulatory effects of polyunsaturated fatty acids (PUFA) on urinary tract tumorigenesis of 275 Wistar rats were evaluated by treating animals with the tumorigenic agent melamine. Rats were fed with formulae containing 6% of 4 varieties of fats: fish oil enriched in n-3 PUFA (FO), corn oil enriched in n-6 (CO), olein containing mainly n-9 oleic acid (O), and 98% stearic acid (SA), the latter two being essential (EFA)-deficient inducers. Two commercially fed control groups with (CM) and without (C) melamine were used. Animals were autopsied at 22-25 and at 36-40 weeks. Hepatic fatty acids showed that O and SA groups were EFA-deficient. Simple well differentiated hyperplasias were significantly higher in the FO lot, whereas dysplasia was increased in the CO, O and SA lots. Most of the animals fed for 36-40 weeks with the three latter formulae developed the more severe lesions. Increased urothelial proliferation was more frequent in EFA-deficient rats. The apoptosis/mitosis ratio was higher in O, SA and CO fed animals with respect to FO and chow ones. Results show that dietary PUFA modulate differentially both normal and pre-neoplastic urothelial proliferation induced by melamine. FO, rich in n-3 fatty acids, showed a strong protective effect.

Delayed-type hypersensitivity and humoral immunity modulation by dietary lipids in a murine model of pulmonary tumorigenesis induced by urethan

Mice fed on semisynthetic formulas containing 15% of corn oil (CO), cod fish liver oil (FO), oleic acid (O) or a mixture of 46% of palmitic and 50% of stearic acids (PS) were treated with urethan during 18 weeks for lung tumor induction. Delayed-type hypersensitivity (DTH) assay, hemagglutination assay and the amount of lung nodes (alveolar adenocarcinomas) were recorded. Results showed significantly greater DTH in CO and FO with respect to O and PS feeding mice; the two last ones induced an essential fatty acid (EFA) deficiency (EFAD). In the O lot there was a non-significant diminution of the humoral response. EFAD animals exhibited a tendency to increase number of lung nodes in relation to CO and FO lots. Splenomegalia was recorded in FO lot. Confront between spleen weight and DTH showed a 72% correlation, suggesting an increase in cellular immunity as increasing unsaturation. It may be concluded that in this suitable model of tumorigenesis the manipulation of dietary lipids may be a strategy to modify the immune system response.

Dietary polyunsatured fatty acids (PUFA) differentially modulate melamine-induced preneoplastic urothelial proliferation and apoptosis in mice

A number of experimental and epidemiological studies indicate that dietary polyunsaturated fatty acids (PUFA) play a modulatory role in the development of several cancers. However, literature on the importance of dietary PUFA in urinary-tract tumourigenesis is scarce, and even contradictory. Therefore, our purpose was to evaluate comparatively, several urothelial cellular parameters linked to neoplasia when 180 BALB/c mice were initiated with the tumourigenic agent melamine and fed with two amounts of different PUFA. In experiment 1, mice were fed with 6% of fish oil (enriched in n-3 PUFA, FO), corn oil (enriched in n-6, CO) and olein (enriched in n-9, an EFA deficiency inducer) formulae plus two chow-fed control lots with (CM) and without (C) melamine treatment. In experiment 2, each of the three varieties of PUFA were offered at 10%. Following 18-22 weeks of melamine treatment, animals were autopsied. The liver fatty acid profile showed a close correlation with the dietary sources, exhibiting in the O group macroscopic and biochemical EFA-deficient (EFAD) characteristics. The frequency of simple urothelial hyperplasias (H) and dysplasia/carcinoma in situ (D/CIS) was significantly lower in the FO group, whereas both types of lesions increased in the CO and O groups, compared to the C and CM mice. Increased proliferation and abnormal luminal localized mitosis were more frequently recorded in EFAD mice, whereas abnormal apoptotic/mitosis ratio increased in both olein- and corn-oil-fed animals. This study shows that dietary PUFA modulate differentially normal and pre-neoplastic proliferation when induced by the tumorigenic agent melamine. Fish oil, rich in n-3 fatty acids, exhibits a clear antipromoting activity, whereas the role of n-6 and n-9 PUFA derivatives needs further research.

Morphological and biological characterization of two mesenchymal murine tumors and the modulation of their growth parameters by n-3 and n-6 polyunsaturated fatty acids

Certain tumor growth parameters (GP) of two mesenchymal transplantable tumors maintained on C57BL/6J mice were characterized. Considering that many experimental, clinical and epidemiologic data have indicated that n-3 and n-6 essential fatty acids are nutrients which may delay the development as well as improve the course of cancer, GPs were evaluated on hosts fed on a semisynthetic formula containing 5% of corn oil (CO) or cod liver oil (CLO) and stock diet (C group). Although survival and latency time of tumor-bearing mice were shortened, other GP as percentage of successful implants were improved by both oils in sarcoma-bearing hosts, suggesting that n-3 and n-6 fatty acids might play a modulating role for the development of these tumors.

Quercetin enhances pretumorous lesions in the NMU model of rat pancreatic carcinogenesis

The effect of dietary quercetin (Q) was evaluated in rats treated with nitrosomethylurea (NMU). Pancreatic nodules and focal acinar cell hyperplasias were observed in groups treated with NMU (87%) and Q-NMU (100%). Although rats with dysplastic foci (27%) were found in the NMU-treated group, Q-NMU treatment resulted in a significantly higher number of rats with dysplastic foci (73%). Furthermore, carcinomas in situ (12%) and one microcarcinoma (4%) were found in these animals. Mitosis was significantly increased and apoptosis was diminished in focal acinar cell hyperplasias of the Q-NMU group. Our present results support a promoting and progressing effect of quercetin in the NMU model of rat pancreatic carcinogenesis.

Differential modulation by dietary n-6 or n-9 unsaturated fatty acids on the development of two murine mammary gland tumors having different metastatic capabilities

It is widely known that dietary lipids can modify the ability of different cancers to grow up and metastasize, especially mammary gland tumors. However, it is still unclear whether n-6 fatty acids behave as tumor promoters in this gland cell population. The effect of different nutritional polyunsaturated fatty acids (PUFAs) on tumor growth parameters of two transplantable murine mammary gland adenocarcinomas of low and high metastatic ability was tested on hosts fed diets with corn oil (CO) rich in 18:2n-6, evening primrose oil (EPO) containing 18:3n-6 (GLA) and a third formula supplemented with olein (O) 18:1n-9, which induces an essential fatty acid deficiency (EFAD). Tumor growth parameters were not adversely affected in the corn oil group with respect to stock-fed controls. Furthermore, metastatic spreading diminished in this group. EPO showed a moderate antitumor activity whereas the n-9-enriched diet showed no clear-cut effects. In both mammary gland tumors, n-6 fatty acid-rich lipids formulae, containing GLA and linoleic acid, were not tumor promoters. On the contrary, both exhibited anticancer activity.

Expression of dynamin immunoreactivity in experimental pancreatic tumors induced in rat by mancozeb-nitrosomethylurea

Dynamins are GTPases which support receptor-mediated endocytosis and bind to several tyrosine kinase receptor-associated proteins known to mediate cell proliferation and differentiation. We have recently established that dynamin expression correlates with normal neuronal (Torre et al., J. Biol. Chem., 269 (1994) 32411-32417) and acinar pancreatic cell differentiation (Cook et al., Mol. Biol. Cell, 6 (1995) 405a). To begin to understand the role of dynamin in neoplastic pancreatic cell differentiation, we have followed the expression of this protein by immunohistochemistry during the development of pancreatic tumors in a mancozeb-nitrosomethylurea (NMU)-based carcinogenesis model recently developed in our laboratory (Monis and Valentich, Carcinogenesis, 14 (1993) 929-933). After a single intraperitoneal injection (50 mg/g body wt) of this carcinogen, rats fed with mancozeb develop pancreatic focal acinar hyperplasia (FACH), dysplastic foci (DYF) displaying acinar-like and ductular-like structures, and ductular-like carcinoma in situ (CIS). After histochemical staining using a monoclonal anti-dynamin antibody, high levels of this protein are consistently observed in well-differentiated acinar tumors (FACH). In contrast, dynamin immunoreactivity is almost undetectable in more advanced lesions showing a ductular-like phenotype (ductular-like DYF and CIS). This change in the expression pattern of dynamin during the progression of acinar into ductular-like DYF and CIS lesions correlates with recent findings from our laboratory showing a differential expression pattern for dynamin in pancreatic cells during embryonic development, with ductular-like precursor cells expressing low levels of this protein. Based upon these results, we conclude that more advanced ductular-like neoplastic cells induced by the carcinogen NMU in rat pancreas behave phenotypically like pancreatic precursor cells in their pattern of expression for dynamin.

Promoting effects of mancozeb on pancreas of nitrosomethylurea-treated rats

Rats were treated with a single i.p. injection of the carcinogen nitrosomethylurea (NMU, 50 mg/kg b.w.) at day three of age. The treatment induced hyperplastic and atypical acinar cell proliferation [focal acinar cell hyperplasia (FACH)]. In this investigation, NMU treated rats were fed AIN-76 diet containing mancozeb (MZ; 100 mg/kg diet), a polymeric complex of ethylene bis (dithiocarbamate) manganese with zinc salt, which is an agricultural fungicide.

EXPERIMENTAL DESIGN

Group one was treated with NMU plus MZ (MZ-NMU), group 2 received NMU alone (NMU), group 3 was fed MZ and saline injected (MZ-SAL) and group 4 was the saline injected control (SAL). Rats were killed at week 24 of age. In MZ-NMU group pancreas there were FACH, dysplastic foci (DYF) and carcinomas in situ (CIS). FACH were larger, coalescent and may show areas of undifferentiated cells (focus within focus). DYF contain proliferative acinar and ductular structures with loss of polarity but no malignant traits. CIS had medullary appearance or consisted of irregularly shaped acini and ducts in stromal framework. Cell had scant cytoplasm and large hyperchromatic, pleomorphic nuclei. DYF and CIS were not seen in MZ group pancreas. The MZ-NMU group had increased mitotic index and greater number of apoptotic cells. There was no pathologic change in MZ-SAL group. Our data indicated that MZ did not cause pancreatic cell proliferation in normal rats whereas it had distinct promoting and progressor effects on NMU initiated pancreatic cells. Thus, a two-stage protocol of pancreatic carcinogenesis was achieved. It is suggested that the NMU protocol may be useful for testing promoter, progressor or inhibitory effect of chemical and physical agents on cell proliferation and transformation of rat pancreas.

Multicentric focal acinar cell hyperplasia and hepatocyte-like cell metaplasia are induced by nitrosomethylurea in rat pancreas

The present report is a study of the effect of the carcinogen nitrosomethylurea (NMU) on pancreas of rats receiving during lifetime a lipid-poor diet, that is essential fatty acid deficient or control diets. Rats fed a commercial stock chow were mated. At day 10 of pregnancy, dams were divided into three groups, that were respectively supplied with the commercial chow, the essential fatty acid deficient or the sufficient diet. Each litter was separated at random in two groups that received at day one of life one intraperitoneal injection of NMU (50 mg/kg b.w.) or saline. After weaning, they were maintained for life with the diet that was supplied to their mothers. The pancreas of NMU-treated rats presented diffuse proliferative changes, focal acinar cell hyperplasias (FACH), and focal hepatocyte-like metaplasia (FHLCM). FACH were expansive presumably preneoplastic growths, showing abnormal differentiation. The number of NMU-treated rats bearing FACH and FHLCM did not significantly differ in the three nutritional conditions.

Postnatal ontogeny of gamma glutamyltranspeptidase activity of pancreas in essential fatty acid deficient rats treated with nitrosomethylurea

The effect of essential fatty acid deficiency and nitrosomethylurea treatment on postnatal levels of pancreatic gamma-glutamyltranspeptidase was studied. A significant increase of gamma-glutamyltranspeptidase activity and changes in fatty acid composition were observed in essential fatty acid deficient rats, from the 14th day of life on. Pancreatic gamma-glutamyltranspeptidase of nitrosomethylurea injected rats in essential fatty acid deficiency and controls was significantly diminished at the 30th day, with no significant differences in both nutritional conditions. The results indicated: 1. Concomitant changes in gamma-glutamyltranspeptidase activity and fatty acid composition of rat pancreas in essential fatty acid deficiency, 2. A significant reduction of pancreatic gamma-glutamyltranspeptidase activity following a single intraperitoneal injection of nitrosomethylurea at day one of life and 3. No interacting effects of essential fatty acid deficiency and nitrosomethylurea on gamma-glutamyltranspeptidase activity of rat pancreas.

Ultrastructure of macrophages of carrageenan granuloma in the rat with data on gamma-glutamyltranspeptidase activity

The present study is an electron-microscopic investigation of granuloma induced in the rat by the subcutaneous injection of 1% lambda-carrageenan in 0.8% sodium chloride. We report on the presence of desmosome-like structures connecting neighbouring macrophages. They consisted of electron-dense plaques, which are closely applied to the cytoplasmic surfaces of the junction. Usually, no bundles of cytoplasmic filaments attached to the plaques were seen. At the intercellular space at the level of the junction, a dense material was observed that was sometimes arranged in a cross-bridge fashion. The lysosomal system was markedly developed and consisted mainly of secondary lysosomes containing a filamentous material that showed intense acid phosphatase activity, which was also demonstrated in Golgi cisternae. A membrane preparation obtained from rat carrageenan granuloma contained gamma-glutamyltranspeptidase activity (GGTP), which is a cell and lysosomal membrane-bound enzyme. The GGTP activity of a similar membrane preparation of guinea pig carrageenan granuloma was six times higher than that of the rat.

Ultrastructural characterization by ruthenium red of the surface of the fat globule membrane of human and rat milk with data on carbohydrates of fractions of rat milk

The fat globules of the cream fractions of human and rat milk were stained with ruthenium red. Under the electron microscope, discrete granules and an amorphous coat of lesser density are seen at the surface of the milk fat globules. Since ruthenium red binds anionic groups selectively, it is probable that the granules contain the greatest concentration of these groups. The cream fraction of rat milk contains hexoses, hexosamines, methylpentoses and sialic acid. Methylpentoses and hexosamines are significantly enriched in the cream fraction. It is concluded that the finding of a surface coat in milk fat globules is in keeping with the Bargmann-Knoop model and suggests a distinct mechanism for carrying certain complex carbohydrates in milk. The role of the negative charges at the outer surface of the membrane coat is maintaining fat globules in suspension and in binding certain cations such as calcium is suggested.