A possible short-term prediction of potential carcinogenicity of chemical compounds in vivo by means of a promoting activity test (PAT).

Carcinogens of chemically unrelated structure and different organotropism cause a mitotic stimulation of adrenocortical epithelia in vivo. A similar response is observed in liver regenerating rats following partial hepatectomy or intoxication by carbon tetrachloride. It is very probable from these and other results that the short-term effect (48 hours p. applic.) is brought about by the emergence of humoral growth stimulators which are evidenced in restorative regeneration and, therefore, accounts for the promoting activity of carcinogens. Special problems resulting from false positive (indomethacin, sodium nitrite) and false negative (7,12-dimethylbenz(a)anthracene, ethionine) findings as well as such of the role of solvents are discussed. The proof of the "contradictory" test result by long-term treatment in the case of trinitroso-trimethylene-triamine, nitroso-ethyltert-butylamine or nitroso-diallylamine has shown the accuracy of this short-term test.