Alpha-acetoxy derivatives of methyl-2-oxopropylnitrosamine: synthesis, hydrolysis rate and bacterial mutagenicity.

N-Methyl-N-2-oxopropylnitrosamine (MOP) induces pancreatic tumors in hamsters. As models for the putative proximate carcinogenic alpha-hydroxy derivatives, we studied N-acetoxymethyl-N-2-oxopropylnitrosamine (AMOP) and N-methyl-N-(1-acetoxy-2-oxopropyl)nitrosamine (MAOP). AMOP was synthesized from aminoacetone by the method of Roller et al. [1975), Tetrahedron Lett., 25, 2065-2068) and MAOP was synthesized by acetoxylation of MOP with lead tetraacetate. The half-lives of AMOP, MAOP and acetoxymethylmethylnitrosamine (ADMN) in aqueous buffer decreased as the pH rose from 5 to 9, with values at pH 5 of 2.8 X 10(4) min for AMOP, 3.2 X 10(3) min for ADMN, and 23 min for MAOP. Mutagenicity was examined in Salmonella typhimurium TA1535, using a pre-incubation at pH 5 without microsomal activation. The mutagenic potency, expressed as revertants/mumole, was 56 for AMOP, 150 for ADMN, and 4.5 X 10(4) for MAOP. Hence, hydrolysis rates at pH 5 were probably important in determining the relative mutagenicity.

The carcinogenicity of N-nitrosodiethanolamine, an environmental pollutant, in Syrian hamsters.

Weekly subcutaneous injections of N-nitrosodiethanolamine (NDELA) at doses of 1000, 500 and 250 mg/kg body wt for life induced tumors in Syrian hamsters which primarily affected the upper respiratory tract. The incidence of these malignant neoplasms arising exclusively from the olfactory region was between 73% (highest dose) and 35% (lowest dose). Lower numbers of neoplasms were found with decreasing frequency in the trachea, larynx and lungs. The results indicate that doses of NDELA lower than 250 mg/kg body wt may also be carcinogenic. Hence, NDELA and its precursors should be regarded as hazardous to human health.

A rapid method for isolating phorbol from croton oil.

The published method for isolating phorbol from croton oil has been improved and made more rapid, mainly by the addition of silica-gel column chromatography. The spectral characteristics are recorded, including the 13C nuclear magnetic resonance (NMR) spectrum.

The effect of N-nitroso-2-methoxy-2,6-dimethylmorpholine on endocrine and exocrine pancreas of Syrian hamsters.

N-Nitroso-2-methoxy-2,6-dimethylmorpholine (MeNDMM), a cyclic derivative of the proposed proximate pancreatic carcinogen N-nitroso(2-hydroxypropyl) (2-oxopropyl)amine (HPOP), is shown to have an almost selective cytotoxic effect on pancreatic beta-cells when a single high dose is given to Syrian hamsters. Hence in this aspect its effect is comparable to that of streptozotocin, which has a glucose moiety similar to the MeNDMM structure. However, contrary to the effect of streptozotocin, low single (subdiabetogenic) doses of MeNDMM led to the development of pancreatic ductular and mixed ductular-insular neoplasms; only 1 animal also had islet cell adenoma. It therefore seems that MeNDMM possesses an affinity for both endocrine and exocrine pancreatic tissue. Other target tissues of MeNDMM were the forestomach, intra- and extrahepatic bile ducts, liver, kidneys and vagina. The tumors of these organs appeared in various incidences, partially in relation to dose and/or survival time. The possible mechanisms of the MeNDMM effect upon the endocrine and the exocrine pancreas is discussed.

Effect of diet on fecal excretion and gastrointestinal tract distribution of unmetabolized benzo(a)pyrene and 3- methylcholanthrene when these compounds are administered orally to hamsters.

3-Methylcholanthrene (3MC) administered p.o. has induced tumors of the hamster gastrointestinal tract (GIT), including the large intestine. This process may depend on the concentration of unchanged hydrocarbon in the GIT contents. Benzo(a)pyrene (BP) ingestion could be involved in human GIT carcinogenesis. Accordingly, male Syrian golden hamsters were fed diets containing BP or 3MC for 10 days. Feces collected during the last two to three days of feeding were analyzed for the unchanged hydrocarbons by KOH:methanol digestion, Florisil column and paper chromatography, and ultraviolet spectrophotometry. With a semisynthetic diet containing 5% Alphacel, 6% corn oil, and 100 microgram BP per g. fecal BP excretion was 0.45% of the dose. Variation of the corn oil content had little effect. Fecal BP excretion was increased 13 times (to 6% of the dose) when 5% wheat brain was used in place of Alphacel and 4.5 times when a commercial diet was used. This suggests that bran adsorbed or sequestered the BP. Water content of the large-intestine contents was increased when the brain diet was fed. Both these factors could affect mucosal exposure to BP. For 3MC, fecal excretion of unchanged hydrocarbon was 14 times greater than for BP under similar conditions. The GIT contents of hamsters fed BP or 3MC showed hydrocarbon concentrations in the order: stomach greater than lower large intestine greater than other sections.

Current knowledge of pancreatic carcinogenesis in the hamster and its relevance to the human disease.

Syrian hamsters present a unique species for induction of pancreatic tumors that in many aspects resemble human pancreatic cancer. The specific response of Syrian hamsters, in contrast to may other rodents, for development of pancreatic ductal (ductular) tumors is not yet known. All pancreatic carcinogens thus far tested show certain common features. They are all nitrosamines that possess or can be metabolized to compounds with 2-oxopropyl- or 2-hydroxypropyl substituents. All but one, N-nitroso-methyl(2-oxopropyl)amine, occur or metabolize to nitrosamines with the ability to cyclize and form structures resembling glucose. Hence it is suggested that this cyclic structure may be responsible for the pancreatic carcinogenicity of these nitrosamines, as has been proposed for the pancreatotropic effect of streptozotocin. It is also of further interest that one pancreatic ductal (ductular) carcinogen, N-nitroso-2-methoxy-2,6-dimethylmorpholine, which possesses a totally cyclic structure, acts, like streptozotocin, as beta-cell cytotoxic and diabetogenic when given in a high single dose. Modification of pancreatic tumor induction has been demonstrated by specific procedures. A high fat diet significantly increases both the incidence and number of induced cancers. Methods for early diagnosis and therapy are being developed and their significance and applicabilities for clinical use will be of major importance. Compared with the other most common types of human cancer, pancreatic cancer has extraordinary characteristics, which make the disease one of the most mysterious of maladies. Consequently, pancreatic cancer represents a serious international problem and requires urgent resolution, especially with regard to its etiology, early diagnosis, prevention, and therapy.

The formation of N-nitrosomethyl(2-oxopropyl)amine from N-nitrosobis(2-oxopropyl)amine in vivo.

After injection of N-nitrosobis(2-oxopropyl)amine (BOP) (10 mg/kg) to male Syrian golden hamsters there were there concentrations of BOP and many of its metabolites in the hamster pancreas compared with the liver and salivary gland. Also, a potential methylating metabolite of BOP, N-nitrosomethyl(2-oxopropyl)amine, was found in both tissues.

Attempted tumor induction with agaritine in mice.

Agaritine, a constituent of the cultivated mushroom of commerce Agaricus bisporus, was administered at concentrations of 0.0625 and 0.03125% in drinking water daily for life to randomly bred Swiss mice. Consumption of the chemical resulted in no detectable carcinogenic action under the experimental conditions. During the course of the experiment, however, a substantial number of animals developed convulsive seizures.

Induction of local epidermal papillomas and carcinoma by selected nitrosamines.

Weekly cutaneous application of N-nitrosobis (2-oxopropyl)amine (BOP) at a dose of 2 mg/application to the neck area resulted in the induction of local papillomas and carcinomas in 80% of Syrian hamsters as early as 19 weeks post-treatment. In addition, a few tumors of internal organs (predominantly in the liver) were also found. N-Nitroso(2-hydroxypropyl) (2-oxopropyl)amine (HPOP), a common metabolite of BOP and BHP, was also found to be an epidermal carcinogen at a dose of 3.8 mg/application. N-Nitrosobis(2-hydroxypropyl)amine (BHP), however, failed to induce any epidermal lesions, when applied similarly at a much higher dose level (%) mg/animal/week). In contrast to BOP and HPOP, BHP induced a high incidence of tumors in internal organs, especially pancreatic cancer, which was the only induced tumor in 5 animals. Skin absorption studies demonstrated that BHP, but not BOP is rapidly absorbed and was detectable in the blood in concentrations of up to 5.5 mug/ml as early as 15 min after carcinogen administration. The possible reasons for the differing effects of BHP and BOP upon hamster skin are discussed.

Metabolism and mutagenicity of N-nitroso-2-methoxy-2,6-dimethylmorpholine in hamsters.

N-Nitroso-2-methoxy-2,6-dimethylmorpholine (MeNDMM) was derived from the cyclic form of N-nitroso-(2-hydroxypropyl)(2-oxopropyl)amine (HPOP), a proposed proximate pancreatic carcinogen for the hamster. MeNDMM was metabolized in vivo by noninbred Syrian golden hamsters to HPOP, which was excreted in urine. In vitro metabolism produced HPOP by cytochrome P450-mediated oxidative demethylation. MeNDMM and HPOP were similarly mutagenic in the Ames Salmonella typhimurium assay, in which hamster liver preparations were used for metabolic activation. MeNDMM, due to its metabolism to HPOP, is probably also a pancreatic carcinogen in the hamster.

Carcinogenic effect of N-nitroso(2-hydroxypropyl)(2-oxopropyl)amine, a postulated proximate pancreatic carcinogen in Syrian hamsters.

N-Nitroso(2-hydroxypropyl)(2-oxopropyl)amine (HPOP) proved to be a potent carcinogen in Syrian golden hamsters. The compound is an in vivo metabolite of N-nitrosobis(2-hydroxypropyl)amine, N-nitrosobis(2-oxopropyl)amine (BOP), and N-nitroso-2,6-dimethylmorpholine and a postulated proximate pancreatic carcinogen in hamsters. As with BOP, HPOP induced a higher incidence of pancreatic ductular adenocarcinomas than did N-nitrosobis(2-hydroxypropyl)amine and N-nitroso-2,6-dimethylmorpholine, and these neoplasms showed a great tendency for invasion and metastasis. Also, HPOP induced tumors of the forestomach, liver, gallbladder, kidneys, and vagina (as did BOP). However, HPOP [unlike BOP, but like N-nitrosobis(2-hydroxypropyl)amine and N-nitroso-2,6-dimethylmorpholine] led to tumor development in the nasal cavity, larynx, trachea, intestine, Harderian gland, lips, and flank organ. The possible mechanisms of HPOP carcinogenicity are discussed.

Carcinogenicity of N-nitrosobis(2-hydroxypropyl)amine and N-nitrosobis(2-oxopropyl)amine in MRC rats.

Weekly sc injections of equitoxic doses of N-nitrosobis(2-hydroxypropyl)amine (BHP) and N-nitrosobis(2-oxopropyl)amine (BOP) to Wister-derived MRC rats induced tumors. The incidence, latency, multiplicity, morphologic type, and distribution of these tumors varied according to the compound given. The esophagus was the main target organ for BHP (100%), followed by the respiratory tract (87%), pharynx (80%), colon and liver (each 73%), kidneys (20%), thyroid gland (20%), and urinary bladder and urethra (each 7%). BOP was ineffective in the esophagus and pharynx but induced a higher incidence of tumors in the kidneys (27%), thyroid gland (60%), urinary bladder (33%), and urethra (73%) and fewer neoplasms in the respiratory tract (20%), colon (67%), and liver (53%). In addition, BOP caused a few, apparently primary, prostate squamous cell carcinomas. The results are compared with results of BHP treatment in Sprague-Dawley rats and with results of BHP and BOP treatment in Syrian golden hamsters.

Induction of tumors in mice with the herbicide succinic acid 2,2-dimethylhydrazide.

A solution of 2% succinic acid 2,2-dimethylhydrazide was given continuously in the drinking water of 6-week-old randomly bred albino mice for the remainder of their lives. The treatment gave rise to tumors of blood vessels, lungs, and kidneys. The tumor incidences in these tissues in the controls were 6, 18, and 0%, whereas in the treated groups the corresponding tumor incidences were 73, 73, and 5%. Light microscopic examination revealed typical angiomas and angiosarcomas of blood vessels, adenomas and adenocarcinomas of lungs, and adenomas of kidneys. The study thus demonstrates the tumorigenicity of the herbicide, succinic acid 2,2-dimethylhydrazide. Since the residues of this chemical occur in fruit, the human population is exposed to it. The environmental implication of this finding and the fact that the hydrazines as a class have tumorigenic properties are discussed.

Formation of methylhydrazine from acetaldehyde N-methyl-N-formylhydrazone, a component of Gyromitra esculenta.

Gyromitrin, acetaldehyde N-methyl-N-formylhydrazone, is a toxin present in edible wild mushroom Gyromitra esculenta. At 37 degrees under different acidic conditions (pH 1 to 3), mimicking the milieu of human stomach, gyromitrin is converted to methylhydrazine, a known tumor inducer in mice and hamsters, through an intermediate, N-methyl-N-formylhydrazine. In addition, methylhydrazine is formed in the mouse stomach after p.o. administration of gyromitrin. These findings imply that consumption of G. esculenta could present a carcinogenic, as well as an acutely toxic, health hazard.

Metabolism of the pancreatic carcinogens N-nitroso-bis(2-oxopropyl)amine and N-nitroso-bis(2-hydroxypropyl)amine in the Syrian hamster.

Metabolisms of the potent pancreatic carcinogens N-nitroso-bis(2-oxopropyl)amine (BOP) and N-nitroso-bis(2-hydroxypropyl)amine (BHP) were studied in male Syrian hamsters. BHP and a new metabolite, N-nitroso-(2-hydroxypropyl)(2-oxopropyl)amine (HPOP), were detected in the urine of hamsters administered BOP and BHP. The rates of HPOP formation from BOP and BHP were determined by the measurement of blood and urine levels at various times after each compound was administered: HPOP was formed readily from BOP, but slowly from BHP. This may explain the different organotropic spectra and carcinogenic potencies of BOP and BHP.

Common metabolites of N-nitroso-2,6-dimethylomorpholine and N-nitroso-bis(2-oxopropyl)amine in the Syrian hamster.

N-Nitroso-2,6-demethylmorpholine (NDMM) administered intraperitoneally to Syrian hamsters was metabolized to N-nitroso-bis(2-hydroxypropy)(2-oxopropyl)amine(HPOP) and N-nitroso-bis(2-hydroxpropyl)amine (BHP) which were identified in blood and urine. The potent pancreatic carcinogen N-nitroso-bis(2-oxoproply)amine was previously shown to form the same metabolites. Preliminary results indicate that NDMM also induces pancreatic and other tumors in Syrian hamsters, similar to those found following BHP treatment.

Intratracheal instillation studies with 7H-dibenzo(c,g)carbazole in the Syrian hamster.

The morphologic effects and the retention and distribution times of single and multiple intratracheal instillations in Syrian hamsters of 7H-dibenzo[c,g]carbazole (DBC) and benzo[a]pyrene (BP) were compared. A single instillation of DBC induced slight changes in the hamster respiratory tract; however, five treatments caused tracheobronchial epithelial proliferation, cell hyperplasia, and occasionally, squamous metaplasia. The particle size of both carcinogens was approximately the same. BP in saline remained longer in the lungs than did DBC in saline. The shortest retention time was recorded when DBC was administered in aqueous solution, whereas multiple doses of DBC in aqueous solution did not markedly affect retention time. DBC passed from the lungs to the intestinal tract and was mainly excreted in the feces.

Induction of mouse lung adenomas by amines or ureas plus nitrite and by N-nitroso compounds: effect of ascorbate, gallic acid, thiocyanate, and caffeine.

Lung adenomas were induced in strain A mice by chronic treatment with N-nitroso compounds (given in drinking water) and with amines or ureas in food plus NaNO2 in drinking water. We studied the effects of varying the concentrations of three N-nitroso compounds and NaNO2 concentration in the morpholine plus NaNO2 and methylurea plus NaNO2 systems. Sodium ascorbate (NaASC) at the highest level tested (11.5 or 23 g/kg food) gave 89-98% inhibition of adenoma induction by the NaNO2 plus piperazine, morpholine, and methylurea systems. In 7 groups, NaASC produced increases of 15-59% in adenoma induction by nitrosomorpholine (NM) and mononitrosopiperazine (MNP), possibly because the mice consumed more of the nitrosamine solution. Adenoma induction by morpholine plus NaNO2 was strongly inhibited by gallic acid, moderately inhibited by caffeine, and unaffected by thiocyanate (all added to the food). Gallic acid inhibited or had no effect on the action of NM and MNP. We discussed the proposal that NaASC (or perhaps gallic acid) be administered with readily nitrosatable drugs.