THE EFFECT OF SUBLETHAL DOSES OF INSECTICIDES ON TRIATOMA-INFESTANS LIPID-SYNTHESIS

The effect of sublethal amounts of d-phenothrin (pyrethroid), phenitro thion (organophosphate), and propoxur (carbamate) on the lipid synthes is in the nymphal integument and fat body of the blood-sucking bug Tri atoma infestans was examined in vivo, in tissue slices, and in cytosol ic fractions. De nova synthesis of lipids was compared for insecticide -pretreated and untreated insects. Lipid biosynthesis, measured as [1- C-14]acetate incorporation, is significantly affected. d-Phenothrin in hibits in vivo incorporation of [1-C-14]propionate, the precursor of m ethyl-branched hydrocarbons in insects. The incorporation of [1-C-14]p ropionate 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 p roduced in the presence of propoxur, but no alteration of the fat body FAS was detected. These data suggest a different mode of action of th e organophosphorate-, pyrethroid-, or carbamate-derived insecticides o n the insect lipogenic enzymes. (C) 1995 Academic Press, Inc.