Chromosomal aberrations in rat lymphocytes treated in vivo with 1-phenyl-3, 3-dimethyltriazene and n-nitrosomorpholine. A further report on a possible method for carcinogenicity screening.

This paper reports the results of screening two carcinogens, N-nitrosomorpholine (NM) and 1-phenyl-3, 3-dimethyltriazene (PDT), for their ability to cause an increase in chromosomal aberrations in rat lymphocytes cultured in vitro after treatment in vivo. NM is a hepatocarcinogen and PDT induces tumours mainly of the central and peripheral nervous system. Both these chemicals gave only weakly positive results in certain other established short term screening tests for carcinogenicity, despite having been shown to cause a significant increase in the number of chromosomal aberrations after a single administration of doses of 250 mg/kg and above. These aberrations were mainly of the isolocus type as opposed to the chromatid type. Significant increases in the number of aberrations of both the isolocus and chromatid types were found after single applications of PDT of 35 and 50 mg/kg. The results obtained are compared with those of other workers using the same compounds in different test systems. Modifications of the system to increase its sensitivity are suggested.