Activation of two environmental mixtures by plant S9

Nitrated and ozonized pyrene mixtures were assayed for their mutagenic activity in the presence or absence of pea S9 using Salmonella typhimurium TA98 as the indicator organism. The plant enzymes increased the mutagenic response of these mixtures above that obtained in the absence of S9. The optimum S9 protein concentration for the activation of the nitrated pyrene mixture at 0.1 microgram was 3.9 mg/plate whereas that for the ozonized pyrene mixture at 33.3 micrograms was 3.2 mg protein/plate. BSA could not replace S9, and NADPH was a required co-factor in the activation of both mixtures by pea S9. Although the nitrated pyrene mixture was determined to consist of approximately 90% 1-nitropyrene, the mutagenic response due to this compound ranged from 30 to 50% of that of the mixture.