A Summary of the Effects of Benzidine, 4,4″-Diaminoterphenyl, 4-Dimethylaminoazobenzene and 4-Cyanodimethylaniline as Observed by the Yeast Group in the Second UKEMS Collaborative Study

Summary

The four UKEMS test compounds (BZD, DAT, DAB and CDA) were assayed for their potential genotoxicity in two species of yeast using a variety of experimental protocols, metabolic activation systems and genetic endpoints.

All four test compounds (including both samples of CDA) showed genetic activity when tested with the appropriate genetic endpoint and activation system. The most extensive range of information was available for the structurally related pair BZD and DAT, which were shown to be potent inducers of lethal damage, point mutation, mitotic gene conversion, mitotic aneuploidy and mitotic crossing-over. However, BZD and DAT had different metabolic requirements, with BZD producing maximum genetic activity in the presence of either exogenous or endogenous metabolic activation systems whereas DAT produced its maximum activity in the absence of exogenous activation systems. The detection of the activity of the pair DAB and CDA appeared to be particularly sensitive to the activation systems used by the investigators and consistent results were observed only in yeast cells with high levels of endogenous activation potential.

The most effective metabolic activation systems for the detection and quantification of the effects of the four test chemicals in yeast was an exogenous preparation derived from Aroclor-induced rat liver microsomes and the endogenous activity of yeast cells grown under high glucose conditions.