Insecticide and Insecticide Metabolite Interactions with Cytochrome P450 Mediated Activities in Maize

• Published in: Pesticide biochemistry and physiology 1996-05, Vol.55 (1), p.10-20
• Main Authors: Baerg, Roger J., Barrett, Michael, Polge, Nicholas D.
• Format: Article
• Language: English
• Subjects: ACIDE CINNAMIQUE; ACIDE GRAS SATURE; ACIDO CINAMICO; ACIDOS GRASOS SATURADOS; Agrochemicals products; BENTAZON; BENTAZONE; Biological and medical sciences; CARBARIL; CARBARYL; CARBOFURAN; CARBOFURANO; Chemical control; CHLORPYRIFOS; CITOCROMO P 450; CITOCROMOS; CLORPIRIFOS; CYTOCHROME; CYTOCHROME P 450; DOSAGE BIOLOGIQUE; ENSAYO BIOLOGICO; EXPERIMENTACION IN VITRO; EXPERIMENTATION IN VITRO; FONOFOS; FORATO; Fundamental and applied biological sciences. Psychology; Generalities; HERBICIDAS; HERBICIDE; INHIBICION; INHIBITION; MALATHION; MALATION; METABOLISME; METABOLISMO; METABOLITE; METABOLITOS; ORGANITE CELLULAIRE; ORGANULOS CITOPLASMICOS; Parasitic plants. Weeds; PERMETHRINE; PERMETRINA; PHORATE; Phytopathology. Animal pests. Plant and forest protection; Pollution effects and side effects of agrochemicals on crop plants and forest trees. Other anthropogenic factors; Pollution effects. Side effects of agrochemicals; TERBUFOS; Weeds; ZEA MAYS
• ISSN: 0048-3575; 1095-9939
• DOI: 10.1006/pest.1996.0030

In vitroassays were used to determine if organophosphate, carbamate, and synthetic pyrethroid insecticides affected the cytochrome P450 monooxygenase (P450) catalyzed hydroxylation of nicosulfuron, bentazon, cinnamic acid, or lauric acid in maize microsomes. All P450 activities were inhibited approximately 50% by carbaryl, and none were inhibited by permethrin. Hydroxylations of nicosulfuron, bentazon, lauric acid, and cinnamic acid were inhibited by malathion 83, 92, 38, and 0%, respectively. Terbufos was only moderately (36%) inhibitory ofin vitroP450 hydroxylation of nicosulfuron. Nicosulfuron hydroxylation was more sensitive than bentazon hydroxylation to inhibition by the insecticides, and both herbicide hydroxylations were more sensitive than lauric acid or cinnamic acid hydroxylations to the insecticides. Since the oxidative metabolites of terbufos were shown to be more potent inhibitors ofin vivonicosulfuron metabolism than terbufos, we examined the effect of terbufos-sulfone onin vivoandin vitroherbicide metabolism. Terbufos-sulfone inhibited metabolism of nicosulfuron and imazethapyr, but not bentazon, in excised corn shoots. Microsomal hydroxylation of nicosulfuron, bentazon, chlorimuron ethyl, and imazethapyr, as well as the desulfuration of malathion, were strongly inhibited (>65%) by terbufos-sulfone. Cinnamic acid hydroxylase appeared to be different from the P450(s) responsible for the pesticide metabolism as it was not inhibited by terbufos-sulfone. However, the data also suggest that malathion, nicosulfuron, bentazon, chlorimuron ethyl, and imazethapyr all share a P450 in common with terbufos-sulfone. Alternatively, there may be separate P450s for the metabolism of the herbicides and malathion, all of which also metabolize terbufos-sulfone. These data show that the inhibition of P450 hydroxylation of nicosulfuron by terbufos-sulfone can explain the injury when maize is exposed to both terbufos and nicosulfuron. However, the insecticides that are the most potentin vitroP450 inhibitors are not necessarily the ones that cause the most herbicide injury in the field.