Induction of sister-chromatid exchanges by pesticides in primary rat tracheal epithelial cells and Chinese hamster ovary cells.

Possible induction of sister-chromatid exchanges by butachlor, paraquat, phorate and monocrotophos was examined in primary rat tracheal epithelial (RTE) and Chinese hamster ovary (CHO) cells. At dose levels that killed less than 50% of the cell population, monocrotophos induced SCEs positively in CHO and RTE cells, while paraquat was positive only in RTE cells. In two trials of the same experiment, paraquat and butachlor in CHO cells, and phorate in either RTE or CHO cells failed to induce a significant number of SCEs at any dose level within the ranges assayed. On the other hand, in RTE cells, butachlor induced a significant number of SCEs at a dose level of 5 micrograms/ml in one trial, but was insignificant in another. The inductions in these assays were, however, dose-dependent. The addition of S9 mixture did not alter the results of SCE induction by these 4 pesticides in CHO cells. RTE cells were more vulnerable to paraquat in cytotoxicity and SCE assays than CHO cells. Cytotoxicities were ranked as butachlor greater than phorate greater than paraquat greater than monocrotophos to CHO cells and paraquat greater than butachlor greater than phorate greater than monocrotophos to RTE cells. Significant cell cycle delays were only found in the treatments with the highest dose levels of butachlor, paraquat and phorate in CHO cells. In addition, this is the first report on SCE induction in RTE cells.