Rapid screening for chemical carcinogens: transforming activity of selected nitroso compounds detected in a transplacental host-mediated culture system.

The transplacental host-mediated hamster cell culture system was used to test a variety of solvents and chemicals of unknown and known (positive and negative) activity for their ability to induce morphologic transformation of cells and growth in agar. Examination of approximately 13,000 colonies of cells from untreated animals yielded no transformants, thus demonstrating no spontaneous transformation in the system. Similar negative results were obtained after animals were treated with the solvents acetone, ethanol, dimethyl sulfoxide, dimethylformamide, and trioctanoin oil. Several known carcinogens, including benzo[a]pyrene, methylnitrosourethane, urethan, and diethylnitrosamine, were positive for transforming activity. Three pesticides, carbaryl, methomyl, and landrin, and their N-nitroso derivatives were tested. All the nitrosated forms had transforming activity, but only one of the pesticides, landrin, was positive. In all experiments conducted, results of the agar-growth test correlated well with tests for morphologic transformation. The transplacental hamster embryol cell culture system therefore detected transforming activity of N-nitroso compounds and some known carcinogens.