C. Clements et al., GENOTOXICITY OF SELECT HERBICIDES IN RANA-CATESBEIANA TADPOLES USING THE ALKALINE SINGLE-CELL GEL DNA ELECTROPHORESIS (COMET) ASSAY, Environmental and molecular mutagenesis, 29(3), 1997, pp. 277-288
Pesticides are broadly used for pest control in agriculture despite po
ssible negative impacts they may pose to the environment. Thus, we exa
mined the DNA damage caused by Five herbicides commonly used in southe
rn Ontario (Canada). Erythrocytes from Rana catesbeiana (bullfrog) tad
poles were evaluated For DNA damage following exposure to selected her
bicides, using the alkaline single-cell gel DNA electrophoresis (SCG)
or ''comet'' assay [Singh et al. (1988): Exp Cell Res 175:184-191; Ral
ph et al. (1996): Eviron Mol Mutagen 28:112-120]. This approach involv
es detection, under alkaline conditions, of DNA Fragments that upon el
ectrophoresis migrate from the nuclear core, resulting in a comet form
ation. The herbicides tested, along with their active ingredients, wer
e AAtrex Nine-O (atrazine), Dual-960E (metalochlor), Roundup (glyphosa
te), Sencor-500F (metribuzin), and Amsol (2,4-D amine). Tadpoles were
exposed in the laboratory For a 24-hr period to several concentrations
of the herbicides dissolved in dechlorinated water. Methyl methanesul
phonate was used as a positive control. The herbicides AAtrex Nine-O-,
Dual-960E-, Roundup-, and Sencor-500F-treated tadpoles showed signifi
cant DNA damage when compared with unexposed control animals, whereas,
Amsol-treated tadpoles did not. Unlike the other responding herbicide
s, Sencor-500F did not show a relationship between dosage and DNA dama
ge. In summary, the results indicate that at least some of the herbici
des currently used in southern Ontario are capable of inducing DNA dam
age in tadpoles. (C) 1997 Wiley-Liss, Inc.