RELATIVE GENOTOXIC ACTIVITIES OF PESTICIDES EVALUATED BY A MODIFIED SOS MICROPLATE ASSAY

The genotoxic activities of 47 pesticides were determined using a modi fied SOS microplate assay in which the induction of beta-galactosidase in E. coli PQ37 was used as a quantitative measure of genotoxic activ ity. The results were compared with those obtained with anethole, curc umin, and capsaicin, a few examples of naturally occurring compounds p resent in foods. The assays were conducted with pesticides dissolved e ither in a suitable solvent, such as 10% DMSO in physiological saline or dispersed in sodium taurocholate micelles, to simulate conditions i n the small intestine from where these substances are normally absorbe d from the diet. 4-Nitroquinoline oxide (4-NQO) served as the referenc e standard of a direct acting mutagen. In micellar form, 4-NQO and 25 of the 47 pesticides tested showed significantly higher genotoxic acti vities than when they were tested in an organic solvent. In micellar f orm the SOS inducing potency of 4-NQO was almost twice as high as in 1 0% DMSO in physiological saline. In taurocholate micelles, the five mo st active compounds had activities in the range of 1,234-3,765 units/m u mol and in the order of decreasing activities they were ranked as fo llows: malathion > dichlorvos > lindane > chlordane > endrin. They wer e significantly less active than 4-NQO (less than 40%). In micellar so lution the naturally occurring compounds, anethole, curcumin, and caps aicin gave activities of 4,594, 998, and 809 units/mu mol, respectivel y. These studies show that genotoxicity may depend upon the environmen t in which cells are exposed to these potential genotoxins. It appears that testing of the more hydrophobic compounds, both synthetic and na turally occurring, are needed. (C) 1995 Wiley-Liss, Inc.