Comparative studies of neoplastic response to a single dose of nitroso compounds. 6. The effect of diethylnitrosamine in Syrian golden hamsters

Effects of nitroso compounds and aromatic amines on fetal tracheal explants

Tracheas were excised from fetal Syrian golden hamsters on the 15th day of gestation. Tracheal explants were cultured in vitro and exposed to different dose-levels of well known carcinogens. We chose two nitroso compounds, N-Methyl-N-nitro-N-nitrosoguanidine (MNNG) and Diethylnitrosamine (DEN) and two aromatic amines, Aminofluorene (AF) and Acetylaminofluorene (AAF). The tracheal explants were treated for 24 h in vitro, then the carcinogens were washed off and the tracheas were kept for 21, 28 or 35 days in culture. After fixation tracheal explants were transversely cut with serial section techniques and scored for morphological changes of the epithelium by light microscopy. Most of the control explants completed differentiation and had a normal morphology at the end of the in vitro culture period. Occasionally we found a decrease of the number of ciliated cells and some areas with squamous metaplasia in the respiratory epithelium. Carcinogen treatment with nitroso compounds led to a significant increase of the morphologic changes of the epithelium. These effects were especially obvious after DEN treatment. Morphologic changes of the epithelium such as metaplasia and hyperplasia were discussed as carcinogen-related events. In vitro exposure with aromatic amines did not induce marked metaplastic or hyperplastic changes in the respiratory epithelium of tracheal explants.

Promoting effect of polybrominated biphenyls on tracheal papillomas in Syrian golden hamsters

Male Syrian golden hamsters were used for an initiation-promotion study of respiratory tract carcinogenesis. Hamsters were given a single subcutaneous dose of 0 or 80 mg N-nitrosodiethylamine (NDEA)/kg body weight and were fed diets containing 0 or 100 mg polybrominated biphenyls (PBB)/kg diet for 140 d. Basal diet was fed from d 140 until the end of the experiment on d 273. The number of tracheal papillomas was significantly increased in hamsters given NDEA and PBB as compared to those in hamsters given only NDEA. Tracheal papillomas were not seen in untreated hamsters or in those not given NDEA and fed diets containing PBB. Nasal tumors occurred at approximately the same incidence in hamsters given NDEA as in those given NDEA and PBB. Results indicate that PBB may promote the development of tracheal papillomas in the hamster.

DNA ethylation in target and non-target organs of hamsters and rats treated with diethylnitrosamine

Kinetics of ethylation of target and non-target organ DNA in vivo by diethylnitrosamine (DEN) was compared in rats and Syrian golden hamsters, since published reports indicate a single dose of DEN induces both kidney and liver tumors in rats and almost exclusively respiratory tract tumors in hamsters. Following treatment with 200 mg DEN/kg, 7-ethylguanine (7-etG) was lost more rapidly from hamster than from rat liver DNA, while O6-ethylguanine (O6-etG) persisted longer in hamster than in rat liver DNA. DNA ethylation was not detected in rat lung (non-target organ), while both 7-etG and O6-etG were quantitated in hamster lung (target organ) following DEN treatment. DNA ethylation in rat kidney DNA was approximately 1/10 of that in liver by 200 mg DEN/kg, and the persistence of 7-etG and O6-etG differed only slightly in these tissues. Ethylation of hamster liver DNA by DEN at doses between 20 and 200 mg/kg, as measured by 7-etG and O6-etG was proportional to the dose of carcinogen up to 160 mg/kg; at larger doses DNA ethylation sharply increased. Differences in the persistence of O6-etG between DEN-treated rats and hamsters cannot solely account for species differences in the organotropism of DEN carcinogenesis.

Carcinogenicity of vinylethylnitrosamine in Syrian golden hamsters

Syrian golden hamsters received weekly s.c. doses of 5.0, 2.5, 1.25 or 0.63 mg/kg b.w. vinylethylnitrosamine (VEN). As dose levels increased, average survival time decreased, tumor multiplicity increased as did the total tumor rate which was between 50% and 100%. The main target of VEN effect was the respiratory tract where a positive dose-response relationship was established for neoplastic growth.