The Effect of Sublethal Doses of Insecticides on Triatoma infestans Lipid Synthesis

Abstract

The effect of sublethal amounts of d-phenothrin (pyrethroid), phenitrothion (organophosphate), and propoxur (carbamate) on the lipid synthesis in the nymphal integument and fat body of the blood-sucking bug Triatoma infestans was examined in vivo, in tissue slices, and in cytosolic fractions. De novo synthesis of lipids was compared for insecticide-pretreated and untreated insects. Lipid biosynthesis, measured as [1- 14C]acetate incorporation, is significantly affected. d-Phenothrin inhibits in vivo incorporation of [1- 14C]propionate, the precursor of methyl-branched hydrocarbons in insects. The incorporation of [1- 14C]propionate after incubation of integumental tissue slices is inhibited by both d-phenothrin and phenitrothion. d-Phenothrin has no influence on the cytosolic fatty acid synthetase (FAS) activity of the fat body or integument. Phenitrothion alters both fat body and integumental FAS activities. A total inhibition of the cytosolic integumental FAS is produced in the presence of propoxur, but no alteration of the fat body FAS was detected. These data suggest a different mode of action of the organophosphorate-, pyrethroid-, or carbamate-derived insecticides on the insect lipogenic enzymes.