THE W/W(+) SMART IS A USEFUL TOOL FOR THE EVALUATION OF PESTICIDES

Genotype-dependent variability in the response of several Drosophila strains to hexamethylphosphoramide (HMPA) has been studied using the white/white(+) (w/w(+)) somatic mutation and recombination test (SMART). Among the tester strains, there were three wild-type laboratory strains (Leiden-S, Oregon-K and 91-C) and three insecticide-resistant strains (Haag-79, Hikone-R and 91-R). The response to HMPA of larvae from a cross between two wild-type strains (Leiden-S and Berlin-K) was also measured. The strains have been evaluated in terms of spontaneous frequencies of mosaic eyes, lowest effective dose and dose - response relationship. Strong variability was found among the strains, the best performance to HMPA being obtained with the strain Oregon-K. In addition, a series of pesticides structurally related to HMPA, such as dimefox, hexamethylmelamine, hexazinone, alachlor, CAM, pirimicarb, dimetilan, thiram and methabenzthiazuron have been tested with the Oregon-K strain. Some of these pesticides had already been shown to be genotoxic in other systems, whereas others have either not been tested or gave negative results in in vitro systems. Although genotoxicity was expressed only within a narrow dose range, all pesticides were genotoxic in the w/w(+) system,vith the Oregon-K strain. Thus, these compounds may be a genotoxic hazard to man. These results suggest the suitability of the strain Oregon-K for genotoxicity testing with the w/w(+) eye mosaic system, although more information about the performance of this strain with other compounds must be obtained. It is concluded that the w/w(+) SMART is an excellent in vivo system able to reveal genotoxicity of promutagens that are difficult to detect with in vitro genotoxicity test systems.