Lm. Kao et al., IN-VIVO EFFECTS OF 2,4-D AND ATRAZINE ON CYTOCHROME-P-450 AND INSECTICIDE TOXICITY IN SOUTHERN ARMYWORM (SPODOPTERA-ERIDANIA) LARVAE, Pesticide science, 45(4), 1995, pp. 331-334
After feeding 2,4-D or atrazine in a diet to southern armyworm (Spodop
tera eridania Cram.) larvae for three days, the effect on total conten
t and activities of cytochrome P450 and on insecticide toxicity were d
etermined. Both 2,4-D and atrazine induced cytochrome P450-catalyzed a
ldrin epoxidation (AE) and methoxyresorufin O-demethylation (MROD). Th
e 2,4-D was a more potent inducer for total cytochrome P450 content, w
hereas atrazine disproportionately increased AE. Both compounds increa
sed MROD significantly. The apparent kinetic characteristics of AE ind
icates that 2,4-D and atrazine induced similar P450 isozymes (K-m 8.78
and 7.80 mu M, respectively), which may differ from the constitutive
isozyme (K-m 3.14 mu M). The 2,4-D-induced cytochrome P450 contributed
to decreased carbaryl and permethrin toxicity, whereas the atrazine-i
nduced cytochrome P450 caused decreased parathion and permethrin toxic
ity. The carbaryl toxicity correlated directly with 2,4-D-induced tota
l P450 content and activities but not with atrazine-induced changes. T
he 2,4-D and atrazine also induced nonspecific esterase activity which
may contribute to permethrin detoxification.