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4119609 
Technical Report 
Metabolism of organophosphorus insecticides. IX. Distribution, excretion and metabolism of dimethoate 
Zayed, SMAD; Hassan, A; Fakhr, IMI 
1968 
HAPAB/68/00183 
Biochem 
7 
HAPAB The distribution and degradation of dimethoate in the adult larvae of Prodenia litura F. was studied using phosphorus-labeled insecticide. For distribution studies, 200 mcg of the insecticide in 20 mcl acetone was applied for each gram of insect. At specified intervals, the unabsorbed insecticide was removed by acetone. Tabulated data show the distribution of labeled phosphorus activity among hemolymph, gut, and fat. One hour after topical application, the larvae were found to contain about 10% of the applied radiodose, with a gradual decrease to about 5% after 20 hr. For the metabolic studies phosphorus-labeled dimethoate, dissolved in acetone was applied topically at a dose level of 750 mcg/g of insect. After 20 hr exposure, chromatographic analysis of the chloroform and water extracts showed that about 40% of the topically applied does was metabolized in 20 hr. An apparent initial oxidation of P=S to P=O constitutes a major metabolic pathway for the insecticide. The hydrolytic metabolites consisted of 24.8% phosphoric acid, monomethyl and dimethyl phosphate (1:1:2), 55.2% thiophosphoric acid, 16.8% carboxy derivative and dimethyl phosphorothioic acid (2:3), and 2.8% of dimethyl phosphorodithioic acid. TOXICOLOGY AND PHARMACOLOGY 68/10/00, 19 1968