In vivo and microsomal metabolism of the pancreatic carcinogen N-nitrosobis(2-oxopropyl)amine by the Syrian golden hamster (original) (raw)
Related papers
Cancer research, 1983
Liver preparations from Syrian golden hamsters catalyze the metabolism of the pancreatic carcinogen N-nitroso-2,6-dimethylmorpholine largely to N-nitroso(2-hydroxypropyl)(2-oxopropyl)amine (HPOP). This reaction is catalyzed by a mixed-function oxidase in the presence of reduced nicotinamide adenine dinucleotide phosphate and oxygen at a rate of 3.8 nmol/min/mg of protein, and it is inhibited by known cytochrome P-450-specific inhibitors. A second potent pancreatic carcinogen N-nitrosobis(2-oxopropyl)amine (BOP) is converted to HPOP by hamster liver in which two enzyme systems appear to be involved. The first is a reductase associated with microsomes which reduces BOP to HPOP in the presence of reduced nicotinamide adenine dinucleotide at a rate of 9.1 nmol/min/mg of protein. The second enzyme is a cytosolic one which catalyzes the same reaction at a slower rate (2.3 nmol/min/mg of protein) and is more effective with reduced nicotinamide adenine dinucleotide phosphate as cofactor. Ba...
Cancer research, 1982
/v-Nitroso-2,6-dimethylmorpholine (NNDM) is an indirect nitrosamine carcinogen which induces ductal adenocarcinoma of the pancreas in the Syrian golden hamster. NNDM is oxidized by normal male hamster pancreas postmitochondrial supernatants (S-9) in the presence of reduced nicotinamide adenine dinucleotide phosphate and oxygen to give three major identi fiable metabolites as measured by high-pressure liquid chromatography. The major products are N-nitrosobis(2-hydroxy-propyOamine, A/-nitroso(2-hydroxypropyl) (2-oxopropyl)amine, and W-nitrosobis(2-oxopropyl)amine. Two other major metab olites have been detected, one which élûtes near the solvent front and is referred to as X,, and one which is more hydrophobic than A/-nitrosobis(2-oxopropyl)amine and is called X2. The rates of formation of A/-nitrosobis(2-hydroxypropyl)amine, /V-nitroso(2-hydroxypropyl) (2-oxopropyl)amine, A/-nitrosobis-(2-oxopropyl)amine, X,, and X? were linear with protein up to a final concentration of 15 mg of pancreatic S-9 per ml. The in vitro metabolism of NNDM by liver and pancreas S-9 and microsomes was compared. Although the liver subcellular frac tions only produced two major metabolites, A/-nitroso(2-hydroxypropyl) (2-oxopropyl)amine and X,, under initial rate con ditions the liver enzymes were greater than 40 times more active than the pancreatic enzymes with respect to the overall metabolism of NNDM. The enzyme(s) for the initial oxidative metabolism of NNDM are associated with the microsomes in the liver and the pancreas. However, the metabolite profiles obtained with pancreatic S-9 preparations are different from those observed with pancreatic microsomes, suggesting the involvement of cytosolic proteins in modulating the pancreatic metabolism of NNDM. Acinar and islet cell S-9 fractions metab olize NNDM at similar rates and exhibit a 2-fold increase in NNDM metabolism over whole pancreas S-9. However, the metabolite profiles for the two cell types are very different. Pretreatment of hamsters with 2,3,7,8-tetrachlorodibenzo-pdioxin results in a marked increase in the rate of NNDM metabolism by both acinar and islet cells. However, the two cell types exhibit different patterns of induction as measured by changes in the metabolite profiles. Pretreatment of hamsters with 2,3,7,8-tetrachlorodibenzo-p-dioxin results in a greater than 20-fold induction of aryl hydrocarbon hydroxylase activity in acinar cell S-9, whereas there is no induction of aryl hydro carbon hydroxylase activity in the islet cell S-9. These results suggest the presence of different forms of the microsomal mixed-function oxidases in these two pancreatic cell types. Duct cells can also metabolize NNDM to an active form as demonstrated by unscheduled DNA synthesis in the nuclei of pancreatic duct epithelial cells after exposure to NNDM. These results provide additional evidence that pancreatic carcinogens are activated within the target cell(s) of the pancreas. MATERIALS AND METHODS Isolation of S-9 and Microsomal Fractions from Liver and Pan creas. Male Syrian golden hamster (Charles River, Wilmington, Mass.)
JOP : Journal of the pancreas, 2000
We have isolated five stable clones from a primary culture of Syrian golden hamster pancreatic duct epithelial cells and have designated them as CK1 through CK5. Here we describe the ability of two of these, CK1 and CK5, to metabolize the pancreas carcinogen N-nitrosobis(2-oxopropyl)amine. The metabolism was assessed as the production of mutated V79 cells in a CK cell/V79 co-culture set up. At a dose of 0.1 mM N-nitrosobis(2-oxopropyl)amine, the CK1 cells produced 82.3 +/- 17.2 mutants/1,000,000 survivors while the CK5 cells produced only 33.2 +/- 10.8 mutants/1,000,000 survivors, both are mean +/- SD (n = 8). Furthermore, both cell types responded differently to two inducers of cytochrome P450 activity, namely Arochlor 1254 and EtOH. Arochlor 1254 treatment did not affect the metabolizing ability of CK1 cells while EtOH treatment resulted in a twofold increase in the mutation frequency. Arochlor and EtOH treatment inhibited the ability of CK5 cells to metabolize N-nitrosobis(2-oxop...
Activation of nitrosamines to mutagens by postmitochondrial fraction of hamster pancreas
Cancer Research, 1980
The nitrosamines 2,6-dimethylnitrosomorpholine (DMNM) and N-nitrosobisà §@.oxopropyl)amine (NBOP) are carcinogens which induce adenocarcinoma of the pancreatic ducts in the Syrian golden hamster. Since both compounds are indirect carcinogens and must be metabolically activated to their car cinogenic form(s) by the enzyme system(s) of the host, the capacity of the mixed-function oxidases in hamster pancreas 9000 x g (5-9) fraction to activate these compounds to mu tagens was studied. The postmitochondrial fraction (S-9) pre pared from pancreas was capable of converting both com pounds to forms mutagenic for Sa!mone!!a typhimurium TA 1535. The mutagenic activity of DMNM with hamster pancreas 5-9 was dose dependent, with 22 ±7 (S.E.) revertants formed 5-9 to activate either DMNM or NBOP to mutagenic metabo lites. This suggests that a different form of the enzyme may be induced by 3-methylcholanthrene and that it metabolizes DMNM and NBOP along predominantly detoxification pathways leading largely to noncarcinogenic metabolites. The absolute requirement by these pancreatic enzymes for reduced nicotin amide adenine dinucleotide phosphate, and their inhibition by a-naphthoflavone and 2,5-diphenyloxazole are strong points of evidence that they are mixed-function oxidases.
The carcinogenic effect of ? oxidized dipropylnitrosamine in mice
Zeitschrift f�r Krebsforschung und Klinische Onkologie, 1978
The chronic effect of 2-HPPN and 2-OPPN was examined in mice. Subcutaneous treatment led to neoplasms in the respiratory tract and liver. Tumor localisation, incidences and types were similar in both treatment groups, and a dose response relationship was observed. The data do not allow us to explain unequivocally the effect of DPN, the parent compound of 2-HPPN 1 and 2-OPPN 1.
Metabolism of the Liver Carcinogen N-Nitrosopyrrolidine by Rat Liver Microsomes
Cancer Research, 1979
This report represents a study of the total metabolism of the hepatocellulan carcinogen, N-nitnosopyrnolidine (NO-PYR), by rat liven microsomes and postmicnosomal supennatant. [2,5-‘4C]NO-PYR, which is totally extractable from aqueous solution with methylene chloride, is converted to radioactive nonmethy lene chloride-extractable products by these fractions. The mi tial rate of conversion to nonmethybene chloride-extractable products follows simple Michaebis-Menten kinetics with an ap parent Km of 3.6 x 1O-@M NO-PYR. The major products of NO-PYR metabolism by rat liver microsomes and postmicro somal supennatant have been isolated and identified. One product of metabolism of NO-PYR is 2-hydroxytetnahydnofuran formed by a-hydnoxylation by the microsomes. In the presence of postmicnosomabsupennatant enzymes, this compound exists only as a transient intermediate which is rapidly converted to 1,4-butanediol or ‘y-hydnoxybutynate. These compounds may be cycled into general cellular metabolism resulting in the production of CO2. Two minor pathways of metabolism have also been found.
Dose- and Sex-related Carcinogenesis by N-Bis(2-hydroxypropyl)nitrosamine in Wistar Rats
Cancer Science, 2000
An initiation-promotion medium-term bioassay for detection of chemical carcinogens, developed in the male F344 rat, uses 0.1% N-bis(2-hydroxypropyl)nitrosamine (DHPN) among five genotoxic chemicals for the initiation of carcinogenesis in multiple organs. To establish this bioassay in the Wistar strain, the effects of two dose levels of DHPN were evaluated on the main DHPN rat target organs: lung, thyroid gland, kidneys and liver. Four groups of male and female animals were studied: Control-untreated group; Multi-organ initiated group (also referred to as DMBDD, based on the initials of the five initiators)-treated sequentially with N-diethylnitrosamine (DEN, i.p.), Nmethyl-N-nitrosourea (MNU, i.p.), N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN, drinking water), N, N′ ′ ′ ′-dimethylhydrazine (DMH, s.c.) and DHPN (drinking water) for 4 weeks; a third group treated with 0.1% DHPN in drinking water for 2 weeks and the last group treated with 0.2% DHPN in drinking water for 4 weeks. The animals were sacrificed after 30 weeks. DHPN at 0.2% induced preneoplasia in the liver and kidneys of rats of both sexes, the number and area of the putative preneoplastic liver glutathione S-transferase-positive hepatocyte foci being significantly increased in these animals. It also induced benign and malignant tumors in female and in male rats. However, there was no relationship between the increased incidence of preneoplastic lesions and tumor development in the 0.2% DHPN-exposed groups of both sexes. DHPN at 0.1% induced only a few preneoplastic lesions in the liver and kidney and no tumors in both male and female rats. A clear dose and sex-related carcinogenic activity of DHPN was registered, although Wistar rats of both sexes showed a relative resistance to the carcinogenic activity of this compound.
Cancer Science, 1998
The modifying effects of quinacrine administration during the post-initiation phase of carcinogenesis were investigated in hamsters treated with N-nitrosobis(2-oxopropyl)amine (BOP). Female Syrian hamsters were given three weekly s.c. injections of BOP at a dose of 10 mg/kg and then 300 or 100 ppm quinacrine in their diet for 37 weeks. Additional groups of animals received the BOP injection alone, or only the 300 ppm quinacrine treatment as BOP-negative controls. At week 40 of the experiment, all surviving animals were killed and development of proliferative lesions was assessed histopathologically. The multiplicity of pancreatic adenocarcinomas and dysplastic lesions per hamster was significantly higher (P< < < <0.01 and P< < < <0.05) in the BOP/Q100 group (1.92 and 1.78) than in the BOP-alone group (1.07 and 0.79). The incidence of hepatocellular adenomas plus carcinomas was also significantly elevated (P< < < <0.05) in the BOP/Q300 and BOP/Q100 groups. In contrast, the multiplicity of lung adenomas plus adenocarcinomas was significantly decreased (P< < < <0.05) by the Q300 treatment. Neither the incidence nor the multiplicity of renal cell tumors (adenomas and carcinomas) or nephroblastomas significantly differed between the BOP-treated groups. Electron microscopic examination revealed an abundance of myeloid lamellar bodies filling the cytoplasm of hepatocytes and pancreatic ductular and acinar cells, and epithelial cells of the gallbladder in the quinacrine-treated animals, the degree being dose-dependent. Our results indicate that quinacrine enhances pancreatic and hepatic carcinogenesis in hamsters induced by BOP.
Chemico-Biological Interactions, 1991
N-Nitrosobis(2-oxopropyl)amine (BOP) and N-nitroso(2-hydroxypropyl) (2-oxypropyl)amine (HPOP) induce pancreatic tumors in the Syrian hamster. BOP and HPOP target the kidneys, esophagus and upper respiratory system in rats, but the pancreas of this species is resistant to the above carcinogens. On the other hand, N-nitrosodimethylamine (DMN) induces hepatic and kidney tumors in the rat, and tumors of the liver and upper respiratory system in the hamster, but it is not known to affect the pancreas of either species. At equimolar doses, ratios of DMN versus BOP or HPOP mediated methylation in hamster liver DNA are 1.6 and 8.1, respectively. Respective ratios in the rat liver are 1.1 and 6.5. However, in both species equitoxic doses of BOP, HPOP and DMN induce similar levels of NT-methylguanine (NT-MeG) in hepatic DNA. At such doses methylation of kidney DNA is 24 and 14 times more extensive in BOP and HPOP than in DMNtreated hamsters. Similarly, ratios of NT-MeG in the pancreas of BOP and HPOP vs. DMN-treated hamsters are 10 and 5, respectively, while in the lung this ratio is 2.2 for both carcinogens. Levels of 06-methylguanine (06-MEG) in the DNA of extrahepatic tissues are substantially greater in hamsters treated with BOP or HPOP than in those treated with an equitoxic dose of DMN. In rats, equitoxic doses of BOP and DMN induce similar levels of NT-MeG and O6-MeG in hepatic, kidney and lung DNA. However, levels of these adducts in pancreatic DNA are 2 times greater following BOP than DMN administration. Ratios of NT-MeG in pancreas, lung and kidney in HPOP vs. DMN-treated rats are 2.1, 2.7 and 2.1,
1985
The c/s isomer of A/-nitroso-2,6-dimethylmorpholine (NNDM), a pancreatic carcinogen for the Syrian golden hamster, is metab olized by hamster liver microsomes to yield A/-nitroso(2-hy- droxypropylX2-oxopropyl)amine (HPOP) as the major product. Rabbit liver microsomes catalyze the metabolism of c/s-NNDM to HPOP at a rate slower than that observed with hamster microsomes, but significantly faster than that obtained with rat microsomes. Pretreatment