EFFECTS OF NITROSO-COMPOUNDS AND AROMATIC-AMINES ON FETAL TRACHEAL EXPLANTS

Tracheas were excised from fetal Syrian golden hamsters on the 15th da y of gestation. Tracheal explants were cultured in vitro and exposed t o different dose-levels of well known carcinogens. We chose two nitros o compounds, N-Methyl-N-nitro-N-nitrosoguanidine (MNNG) and Diethylnit rosamine (DEN) and two aromatic amines, Aminofluorene (AF) and Acetyl- aminofluorene (AAF). The tracheal explants were treated for 24 h in vi tro, then the carcinogens were washed off and the tracheas were kept f or 21, 28 or 35 days in culture. After fixation tracheal explants were transversely cut with serial section techniques and scored for morpho logical changes of the epithelium by light microscopy. Most of the con trol explants completed differentiation and had a normal morphology at the end of the in vitro culture period. Occasionally we found a decre ase of the number of ciliated cells and some areas with squamous metap lasia 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 treat ment. Morphologic changes of the epithelium such as metaplasia and hyp erplasia were discussed as carcinogen-related events. In vitro exposur e with aromatic amines did not induce marked metaplastic or hyperplast ic changes in the respiratory epithelium of tracheal explants.