RESUMEN
Two commercial preparations of atrazine and zineb were tested on a diploid D7 strain of the yeast Saccharomyces cerevisiae using cells from logarithmic growth phase (with a high level of cytochrome P-450) and from stationary growth phase. The compounds induced marked increases of both gene conversion and point mutation frequencies in the logarithmic phase cells, while in the stationary phase no genotoxic effect was observed. The results obtained employing TA98 and TA100 strains of Salmonella typhimurium (Ames test) confirmed that neither atrazine nor zineb were mutagenic. The interaction between zineb and chlorophyllin, a known antimutagen in several biological systems, has been evaluated in yeast cells from logarithmic growth phase. The results showed that chlorophyllin seems to have a protective role against the genotoxic effects of zineb. The in vivo effects on cytochrome P-450 content (Cyt. P-450) and on monooxygenase activities were examined in hepatic microsomes of induced animals (rat, pig, and rabbit) 24 hrs after acute treatment. The results obtained with atrazine showed that it caused different effects in the three animal species. Preliminary data with zineb indicated that it can act both as an inducer or as an inhibitor of the monooxygenase system, depending on the dose used.