The peritoneal cell carcinogenicity test: a new short-term test system in rats.

A new carcinogenicity test system in rats, in vivo-in vitro, is discussed in the light of the validation results obtained so far. The new test lasts only 3 weeks and it involves the use of peritoneal cells as target cells. Colony growth in soft agar is considered as a criterion for cell transformation which, in turn, is taken as evidence for a carcinogenic potential of the agent tested. There was an absence of colony growth in 98% of the cultures made from the 225 control rats tested so far. Negative results were also observed with 2 known non-carcinogens, whereas positive cultures were observed for 7 known carcinogens belonging to 5 different classes. These results suggest that the chosen target cells are sensitive enough to detect the carcinogenic effect of agents applied in vivo even if these are strictly organotropic in their action. Several interesting areas of future research are discussed.