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PubMed1992

Hepatic fibrosis in rats produced by carbon tetrachloride and dimethylnitrosamine: observations suggesting immunoassays of serum for the 7S fragment of type IV collagen are a more sensitive index of liver damage than immunoassays for the NH2-terminal propeptide of type III procollagen.

Liver fibrosis was induced in rats both with carbon tetrachloride and dimethylnitrosamine. Assays were performed on steady-state levels of messenger RNAs in the liver for several collagens and basement membrane components. The results indicated marked increases in the steady-state levels of messenger RNA for type I collagen, type III collagen, type IV collagen and the B2 component of laminin. In the same animals, immunoassays were performed for serum levels of the N-terminal propeptide of type III procollagen and the 7S fragment of type IV collagen. The results demonstrated an increase in the serum levels of 7S fragment that occurred early and closely paralleled the increase in the steady-state levels of messenger RNA for the alpha 1(IV) chain of type IV collagen. In contrast, no significant increase was seen in the serum levels of the N-propeptide of type III procollagen. The results suggest that immunoassays for 7S fragment of type IV collagen in serum are a more sensitive index for liver cell damage and fibrosis than assays for the N-propeptide of type III procollagen. The results suggest that greater attention should be paid to assays of 7S fragments in assessing hepatic fibrosis in man.

Animals↗
PubMed1999

Suppressive effects of estradiol on dimethylnitrosamine-induced fibrosis of the liver in rats.

As a model for the analysis of the fibrosuppressive role of estradiol, hepatic fibrosis was induced in male and female rats by the administration of a single dose of dimethylnitrosamine (DMN). The fibrotic response of the male liver after DMN treatment was significantly stronger than that of the female liver. In the male DMN model, estradiol reduced hepatic mRNA for type I and III procollagens and the tissue inhibitor of metalloproteinase-1 (TIMP-1), as well as deposition of type I and III collagen protein total hepatic collagen and malondialdehyde (MDA), a product of lipid peroxidation. Concomitant administration of a neutralizing antibody against rat estradiol enhanced fibrogenesis, as judged by the same parameters. Ovariectomy in the female model had a fibrogenic effect, inducing the hepatic expression of both types of procollagen and TIMP-1; in addition, the number of alpha-smooth muscle actin (alpha-SMA)-positive cells in the liver increased; estradiol replacement was fibrosuppressive in the castrated-female model. In rat hepatic stellate cells incubated in primary culture with estradiol, cell number, type I collagen production, and alpha-SMA expression were all reduced. These findings suggest that estradiol suppressed the induction of hepatic fibrosis, and may in part underlie the more rapid progression in males of hepatic fibrosis and its complications.

Animals↗
PubMed1979

Methylation of DNA in target and non-target organs of the rat with methylbenzylnitrosamine and dimethylnitrosamine.

The sites of labelling of DNA with [14C]methyl groups from methylbenzylnitrosamine and dimethylnitrosamine were studied in rat oesophageal epithelium and liver. All four combinations of tissue and carcinogen were studied. Tissues were labelled in vitro and the DNA contained therein purified and hydrolysed (pH 1, 37 degrees C) to free purines and apurinic acid. Quantitative analysis was performed with the aid of thin-layer chromatography. The apurinic acid and 7-methylguanine fractions were found to be extensively labelled. Smaller amounts of radioactivity were found in O6-methylguanine and some of the methylated adenines. The same carcinogen produced different patterns of labelling is oesophageal and liver DNA. The proportion of O6-methylguanine to 7-methylguanine was higher when the methylating agent was a carcinogen specific for the organ.

Animals↗
PubMed1981

Studies on lung tumours. V. Susceptibility of mice to dimethylnitrosamine-induced tumour formation in relation to H-2 haplotype.

Male mice of the strain A/Sn, of its congeneic partner strain A.SW, C57BL/10ScSnA (abbreviated: B10), and of two congeneic strains on a B10 background (B10.A and B10.AKM) were investigated for their susceptibility to lung tumour induction by dimethylnitrosamine (DMN) administered either by intraperitoneal injection or in the drinking water. Strain B10 (haplotype H-2b) proved to be very resistant, whereas strains A/Sn (H-2a) and A.SW (H-2s) were highly susceptible. The introduction of the haplotypes H-2a and H-2m in the resistant strain B10 resulted in a significant increase in sensitivity towards DMN-induced lung tumour formation. Lung tumour incidences in male (B10.A x B10)F hybrids, receiving DMN in drinking water, were found to be intermediate between, and significantly different from, the incidences of identically-treated parent strains B10.A and B10. Males of back-cross (B10.A x B10) x B10 BC proved to be of low susceptibility to lung tumour formation by DMN, tumour incidence being very low and not significantly different from that observed in identically-treated B10 males. It is concluded that, at least in the model system of B10-derived congeneic strains, H-2 haplotype is one of the factors important in determining susceptibility towards DMN-induced lung tumours. Comparison of C3Hf (H-2k), C3H/Sn (H-2k) and the latter's congeneic strains C3H.B10 (H-2b) and C3H.NB (H-2p) of male mice showed that these strains were moderately susceptible to both lung tumour and hepatoma formation by DMN. Accordingly, the presence of an H-2 haplotype from a lung-tumour-resistant strain (H-2b, B10) on the background of a strain of intermediate susceptibility (C3H) does not decrease susceptibility to lung tumour formation. The results were considered in the light of the H-2 haplotype dependence of spontaneous lung tumours, and consequently attention has been paid to the histological types of the induced and spontaneous lung tumours.

Adenocarcinoma, Bronchiolo-Alveolar↗
PubMed1981

Enhancing effects of dimethylnitrosamine on aflatoxin B hepatocarcinogenesis in rats.

In a study of possible enhancing effects of dimethylnitrosamine (DMN) on aflatoxin B1 (AFB1) hepatocarcinogenesis, male Buffalo strain rats were fed diets containing 1 ppm AFB1, 25 ppm DMN, and a combination of 1 ppm AFB1 and 25 ppm DMN (AFB1 + DMN). The diets were replaced by chow pellets after 6 months, and animals were killed 3, 6, 9 and 12 months after the onset of the experiment. In the untreated control group animals were free of hepatocellular carcinoma but the treated groups fed AFB1, DMN and AFB1 plus DMN developed hepatic lesions ranging from multiple cysts, altered cell foci and neoplastic nodules to hepatocellular carcinomas. Hepatocellular carcinomas developed in 79%, 45% and 5% of rats fed AFB1 plus DMN, AFB1 and DMN respectively at the end of the experiment. Multiple cysts were also found in all periods in animals fed AFB1 plus DMN, whereas rats fed AFB1 and DMN separately developed a few multiple cysts by the end of the experiment. These findings suggest that DMN potentiates the hepatocarcinogenesis induced by AFB1 in rats.

Aflatoxin B1↗
PubMed1984

Dimethylnitrosamine genotoxicity in rat liver primary cell cultures with low cytochrome P-450 levels.

Liver primary cell cultures (LPCC) with decreasing concentrations of cytochrome P-450 were used to investigate the genotoxicity of the hepatic carcinogen dimethylnitrosamine (DMN) and the correlation between DMN genotoxicity and cytochrome P-450 levels. Hepatocytes were isolated from partially hepatectomized rats and incubated with [3H]thymidine; single-strand DNA molecular weight was determined by alkaline sucrose sedimentation. The molecular weight of DNA decreased 50% in LPCC plated either 2 or 24 h before being treated for 24 h with 70 micron DMN. Cytochrome P-450 content was 188 pmol per mg protein in freshly isolated hepatocytes, whereas it was 70 and 32 pmol per mg protein in hepatocytes that had been cultured 24 and 48 h, respectively. Incorporation of 14C into acid-insoluble material was the same in LPCC exposed 24 h to [14C]DMN starting either 2 or 24 h after cell plating. At non-toxic concentrations (0.01-1 microM), SKF 525-A, an inhibitor of mixed-function oxidase enzymes, inhibited approximately 20% of the binding of 14C from [14C]DMN to acid-insoluble material in LPCC plated either 2 or 24 h before they were exposed to DMN for 24 h. Hepatocyte cultures exposed to the direct-acting alkylating agent N-methyl-N'-nitro-N-nitrosoguanidine (at concentrations ranging between 6.8 X 10(-8) and 6.8 X 10(-5) M) starting 2 and 24 h after plating, exhibited significant unscheduled DNA synthesis. These results indicate that DMN genotoxicity was similar in LPCC differing considerably in cytochrome P-450 levels, and they suggest that DMN genotoxicity in these cultures is due mainly to similar DMN activation than to decreased DNA repair.

Animals↗
PubMed2006

Pharmacokinetics and therapeutic effects of oltipraz after consecutive or intermittent oral administration in rats with liver cirrhosis induced by dimethylnitrosamine.

Pharmacokinetics and therapeutic effects of oltipraz were evaluated after consecutive (once per day at 30 mg/kg/day for 7 and 14 days) or intermittent (once per week at 100 mg/kg/week for 1-3 weeks) oral administration to rats with liver cirrhosis induced by dimethylnitrosamine. The AUC of oltipraz was significantly greater in cirrhotic rats than controls (890 compared with 270 microg . min/mL) due to impaired liver function in cirrhotic rats. However, the AUC values after consecutive 7 (421 compared with 753 microg . min/mL) and 14 (309 compared with 821 microg . min/mL) days oral administration of oltipraz in cirrhotic rats were significantly smaller than those in respective vehicle-treated cirrhotic rats. Moreover, the AUC values after intermittent 2 and 3 weeks in cirrhotic rats were also significantly smaller than that in 1 week vehicle-treated cirrhotic rats (2370 and 1690 compared with 4760 microg . min/mL). This could be due to induction of CYP isozymes and considerably greater numbers of normal liver cells in cirrhotic rats by oral administration of oltipraz. Improved liver function by oltipraz in cirrhotic rats was proved by liver microscopy; livers are free of significant fibrosis, although evidence of bridging necrosis is still present in many rats.

Administration, Oral↗
PubMed1995

p53 status in spontaneous and dimethylnitrosamine-induced renal cell tumors from rats.

Rats carrying the Eker tumor-susceptibility mutation (Eker rats) are predisposed to developing renal cell carcinoma. Rats heterozygous for the Eker mutation develop spontaneous multiple bilateral renal cell tumors by the age of 1 yr. In a previous study, Eker-mutation carrier and noncarrier rats were exposed to the renal carcinogen dimethylnitrosamine (DMN), and male rats carrying the Eker mutation exhibited a 70-fold increase in the induction of renal adenomas and carcinomas when compared with noncarrier rats. In this study, spontaneous and DMN-induced rat renal cell tumors (adenomas and carcinomas) were analyzed for mutations of the p53 gene by direct sequencing of cDNA polymerase chain reaction products. There were no mutations in p53 cDNA derived from renal tumors from six untreated rats. Mutations were found in one of 15 of the DMN-induced tumors: a transition at codon 140, CCT-->CTT, in a renal adenoma. Additionally, seven cell lines derived from spontaneous renal cell tumors did not contain mutations in p53. The low frequency of p53 mutations (one of 21 renal cell tumors and none of seven cell lines derived from renal cell tumors) indicates that the development of both spontaneous and carcinogen-induced renal tumors involved a non-p53-dependent pathway. As p53 is infrequently mutated in human renal cell carcinomas and in rat renal mesenchymal tumors, it is likely that a tumor suppressor gene or genes other than p53 are involved in the development of renal cancer.

Adenoma↗
PubMed1994

Changes in secondary structure of DNA of rat embryos following treatment with 1,2-diethylhydrazine and dimethylnitrosamine in vivo.

1,2-Diethylhydrazine (DEH) and dimethylnitrosamine (DMN) are indirect acting carcinogens that require metabolic activation to exert their potency. DEH is a transplacental carcinogen and teratogen in Wistar rats when administered by i.p. injection on day 12 of gestation. DMN is embryotoxic during this period. In this study, gravid Wistar rats were injected i.v. with DEH (10, 15, or 20 mg/kg) or i.p. with DMN (10 or 30 mg/kg) and the effects on the embryos 24 hours later were observed. Controls were similarly injected with saline vehicle. The incidence of resorptions increased after treatment with 20 mg DEH/kg. DEH treatment also resulted in decreases in embryo wet weights and total DNA that were not dose dependent. Treatment with DMN did not affect embryonic wet weights and total embryonic DNA amount when compared to the saline-treated controls. The effects of DEH and DMN on DNA synthesis in vivo were monitored by injecting [methyl-14C]-thymidine 1 hour prior to embryo death. DEH induced significant increases in thymidine incorporation into embryo DNA but the increases were not proportional to the doses administered. DNA synthesis was significantly decreased in embryos treated with 30 mg DMN/kg. The DNA of treated and control embryos was fractionated by benzoylated DEAE-cellulose (BD-cellulose) chromatography to determine differences in DNA secondary structure following treatment. BD-cellulose chromatography separates double-stranded DNA from DNA containing single-stranded regions by step elution with 1 M NaCl solution and caffeine solution, respectively. Embryonic DNA was monitored by in vivo labelling with [methyl-3H]-thymidine on days 6 and 7 of gestation. Significant dose dependent increases in percentages of caffeine-eluted DNA (%CE-DNA) compared to controls were detected after treatment with 10, 15, and 20 mg DEH/kg and 10 and 30 mg DMN/kg. The relative %CE-DNA is expressed as the ratio of %CE-14C-labeled DNA to %CE-3H-labeled DNA. Litters treated with 10, 15, and 20 mg DEH/kg had relative %CE-DNA values significantly lower than controls. The results support the hypothesis that initiation mechanisms of transplacental carcinogenesis and teratogenesis are different. The pertinence of %CE-DNA and relative %CE-DNA values to the study of transplacental carcinogenesis and teratogenesis is discussed.

Animals↗
PubMed1994

Lack of promoting effect of proline on bile duct cancer development in dimethylnitrosamine-initiated hamster livers.

Bile duct hyperplasia caused by proline is believed to represent a chemical effect of the liver fluke, Fasciola hepatica, and the resultant cell division might be expected to play a role as a tumor promoter. To investigate the potential promoting effect of proline on bile duct cancer development, Syrian hamsters were therefore divided into 8 treatment groups: dimethylnitrosamine (DMN) + proline intraperitoneally (i.p.); DMN + proline s.c.; DMN + saline i.p.; DMN + saline s.c.; proline i.p.; proline s.c.; saline i.p.; and saline s.c. DMN was injected i.p. at 20 mg/kg to the animals 2 weeks prior to commencement of proline treatment, whereby 1 ml of a 2 M solution was given by i.p. or s.c. injection 3 times a week for 20 weeks. At the end of week 42, assessment of preneoplastic lesion development did not reveal any significant modulating influence of proline on DMN-initiated lesion development nor did it itself cause persistent bile duct hyperplasia.

Animals↗
PubMed1998

Molecular dissection of dimethylnitrosamine (DMN)-induced hepatotoxicity by mRNA differential display.

Differential display reverse transcription-polymerase chain reaction (DDRT-PCR) was used to catalogue altered hepatic transcript expression during dimethylnitrosamine (DMN) exposure in vivo. Mice were administered DMN (1.5 or 5 mg/kg) or vehicle (phosphate-buffered saline) i.p. once daily for up to 7 days, and livers were collected 6 h post-injection. Total RNA was reverse transcribed and cDNA subsets were selectively amplified by PCR. DDRT-PCR products were fractionated on denaturing polyacrylamide gels, and differentially expressed bands were excised, reamplified, and subsequently cloned into a plasmid vector. This study identified 23 cDNAs that were induced and 25 cDNAs that were suppressed during DMN exposure. Altered expression during DMN exposure for cDNA clones was confirmed by Northern blotting, RNase protection, or in situ hybridization analyses. DNA sequence information indicated that four cDNAs suppressed during DMN exposure encode cytochrome P450 isoenzyme-cholesterol 7 alpha-hydroxylase (CYP7), a monokine, a myeloid cell differentiation protein, and mouse major urinary protein (MUP). We further observed a DMN-induced increase in transcripts for complement factor 3 (C3) and serum amyloid A (SAA). In contrast, the remaining differentially expressed transcripts detected by DDRT-PCR during DMN exposure demonstrated no similarity to sequences present in Genbank, suggesting that they may encode previously unreported gene products. In situ hybridization showed MUP transcripts to be expressed by hepatic centrilobular areas that undergo necrosis during subchronic DMN exposure. Thus, the utilization of DDRT-PCR has identified several differentially expressed hepatic mRNAs associated with various doses and stages of DMN exposure.

Alkylating Agents↗
PubMed2000

Enhancing effects of 2-amino-4,5-diphenylthiazole-induced polycystic kidneys on renal carcinogenesis in rats treated with dimethylnitrosamine.

The effects of the polycystic kidney environment on dimethylnitrosamine (DMN)-induced renal carcinogenesis were investigated in rats. In Experiment 1, male Wistar rats were given 25 or 10 ppm DMN in their drinking water and simultaneously administered 1% 2-amino-4,5-diphenylthiazole (DPT) in the diet for 30 weeks. DPT-induced polycystic kidney was associated with a significant increase in the number of renal cell tumors and incidence of mesenchymal tumors in the 25 ppm DMN + DPT group and the incidence of atypical tubules in the 10 ppm DMN + DPT group. PCNA labeling indices of cystic renal tubules in DPT-treated rats were significantly higher than for corresponding noncystic tubules. In Experiment 2, PCNA indices of renal tubules in 10 ppm + DPT rats and immunohistochemically CYP2E1-positive renal tubules in DPT-treated rats were demonstrated to be significantly increased on day 14. CYP2E1 mRNA expression in the kidneys of DPT-treated rats showed a fivefold increase over constitutive levels. The results thus indicate that DPT induction of polycystic kidneys enhances DMN-induced renal carcinogenesis in rats, with DPT-induced elevated cell proliferation and CYP2E1 expression in renal tubules as possible underlying mechanisms.

Animals↗
PubMed2001

Increased oxidative stress in dimethylnitrosamine-induced liver fibrosis in the rat: effect of N-acetylcysteine and interferon-alpha.

Oxidative stress may represent a common link between chronic liver damage and hepatic fibrosis. Antioxidants and interferon seem to protect against hepatic stellate cell (HSC) activation and liver fibrosis. This study evaluated (1) the effect of the profibrotic agent dimethylnitrosamine (DMN) on the hepatic oxidative balance in the rat; (2) the role played by the antioxidant agent N-acetylcysteine (NAC); and (3) the antifibrotic effects of two different types of interferon-alpha: recombinant alpha-2b (rIFN-alpha) and leukocyte alpha (LeIFN-alpha). Five groups of rats received: (1) saline; (2) DMN; (3) DMN + NAC; (4) DMN + rIFN-alpha; and (5) DMN + LeIFN-alpha. Oxidative balance was evaluated by hepatic glutathione, TBARs, protein carbonyl, and sulfhydryl determination. Fibrosis was determined by hepatic hydroxyproline content and fibronectin (FN) staining (immunohistochemistry). DMN rats showed a diffuse FN deposition, an impaired oxidative balance, and higher hepatic hydroxyproline levels compared to that of controls. NAC administration significantly reduced FN deposition, increased hepatic glutathione, and decreased TBARs and protein carbonyls. Administration of IFN-alpha exerted different effects according to the type used. Both IFNs decreased FN deposition; however, LeIFN-alpha significantly improved histology and oxidative parameters compared to those of untreated DMN and rats treated with rIFN-alpha. This study shows the role of free radicals in this model of hepatic fibrosis; the protective effect of NAC against liver fibrosis; and the antifibrotic effect exerted by IFN-alpha (particularly LeIFN-alpha) independent of its antiviral activity.

Acetylcysteine↗
PubMed1980

Decreased hepatotoxicity of dimethylnitrosamine (DMN) following chronic alcohol consumption.

Compared to controls receiving physiological saline, the i.p. administration of dimethylnitrosamine (DMN) on 5 consecutive days to rats fed a nutritionally adequate liquid diet resulted 24 hours after the last injection of significant increases in glutamic dehydrogenase (GDH), glutamic oxylacetate transaminase (GOT), and glutamic pyruvate transaminase (GPT) activities in the serum, indicating a striking hepatotoxic effect of this compound. This was confirmed by the histological demonstration of massive centrolobular necrosis. Conversely, following pretreatment of the rats with an ethanol containing liquid diet for 23 days and subsequent administration of DMN the increases of serum enzyme activities and massive centrolobular necrosis could not be observed. These results therefore suggest that chronic alcohol consumption protects from hepatotoxicity due to DMN, most probably due to an enhancement of detoxifying pathways of the parent component or one of its toxic metabolites.

Alanine Transaminase↗
PubMed1980

Metabolizing activities of postmitochondrial liver fractions (S-9) on benzo[a]pyrene and dimethylnitrosamine.

The mutagenic activity of the carcinogens benz[a]pyrene and dimethylinitrosamine after being metabolised by postmitochondrial liver fractions (S-9) from rats, Syrian hamsters and rabbits was estimated in the Ames' test. The liver donors were pretreated with phenobarbital, 3-methylcholanthrene, PCB (Delor 106) or peanut oil. Parallel to the mutagenicity tests, enzymes of S-9 such as dimethylnitrosamine demethylase and aryl hydrocarbon hydroxylase were estimated and their activity evaluated with reference to the results of the Ames' test.

Animals↗
PubMed1994

An interleukin-1 receptor antagonist decreases fibrosis induced by dimethylnitrosamine in rat liver.

The main pathological feature of liver fibrosis is the accumulation of extracellular matrix associated with hyperplasia and activation of perisinusoidal (Ito) cells (PSC) to myofibroblast-like cells. Interleukin-1 enhances collagen synthesis by increasing the proliferative activity of cultured PSC and has been implicated in the pathogenesis of hepatic fibrosis. Interleukin-1 receptor antagonist (IL-1ra) can block the binding of IL-1 to its receptors and act as a natural inhibitor of IL-1. We have examined whether the administration of IL-1ra can interfere with the development of experimental cirrhosis induced by dimethylnitrosamine (DMN). Rats were divided in three groups and received respectively DMN, DMN + IL-1ra and IL-1ra. For each group the collagen content of the hepatic tissue and the volume density of the inflammatory infiltrate were measured. Immunostaining for laminin and alpha-smooth muscle actin were also performed. In animals given DMN + IL-1ra we observed a decreased deposition of laminin and collagen, and a decreased number of laminin-positive PSC and of alpha-smooth muscle actin reactive cells, compared with animals receiving DMN alone. The present findings suggest that the early activation of PSC in vivo is at least in part mediated by IL-1 and confirm that the administration of IL-1ra may be of interest in modifying the biological effects of IL-1.

Actins↗
PubMed1976

Comparative studies of neoplastic response to a single dose of nitroso compounds. 5. The effect of dimethylnitrosamine in Swiss, ASW/SN and A-strain mice.

The tumorigenic effect of dimethylnitrosamine given once at 5 different dose levels was compared in adult Swiss, ASW/SN and A-strain mice. Considering the overall tumour incidence, at the highest dose level an increase was found in Swiss and ASW/SN mice, but not in A-strain animals. However, the effect of treatment was unequivocal for lung neoplasms. The rate of carcinomas rose significantly in all 3 strains, although a clear dose response-relationship could be established only in Swiss and ASW/SN mice. A dose-dependent effect for adenomas was found solely in Swiss mice.

Adenoma↗
PubMed1976

Influence of disulfiram on the organotropy of the carcinogenic effect of dimethylnitrosamine and diethylnitrosamine in rats.

In former studies in rats and mice it was shown that the acute toxicity of dimethylnitrosamine (DMNA) and diethylnitrosamine (DENA) is reduced by additional treatment with tetraethylthiuramdisulfide [(Disulfiram, Antabus (DSF)]. In long-term experiments in 40 rats given 500 mg/kg DSF/week the substance did not show carcinogenic effects, however, influenced the action of the nitrosamines. DENA, which was administered to 38 rats in a dosage of 20 mg/kg/week, induced liver tumors in 90% of the animals; in 29% besides some precancerous stages predominantly malignant carcinomas of the oesophagus were seen. DMNA when given to 31 rats in a dosage of 4 mg/kg/week induced liver tumours in 55% of the animals. 26 rats were treated with a combination of 500 mg/kg DSF/week and 20 mg/kg DENA/week. In only 31% of the animals of this group liver tumors were found, however, 81% of them besides some precancerous stages showed predominantly carcinomas of the oesophagus. The combination of 500 mg/kg DSF/week and 4 mg/kg DMNA/week induced only 1 liver tumor (=3%) out of a group of 29 animals, whereas 59% of them showed squamous cell carcinomas of the paranasal sinus that were not seen when DMNA was given alone.

Animals↗