Distribution and incorporation of orally ingested cyromazine into house fly eggs

In addition to milk and sugar solution provided ad libitum a 839 ppm [C-14] cyromazine was fed to female house flies at the rate of 1 muI/day for up to 4 days. The radioactivity excreted ranged from 85 to 90% of the total inge sted after 1 or 4 days, respectively The radioactivity retained in the body was distributed in hemolymph (0.9%), ovary including eggs (1%), and carcas s (0.7%). When the female flies were allowed to deposit eggs, 0.6% of the r adioactivity was found in the eggs deposited in the first gonotrophic cycle , which consequently reduced the radioactivity present in the ovary. These results clearly demonstrate that cyromazine ingested by female flies is inc orporated into eggs and inhibits larval development in the Fl generation. T o study me mechanism of cyromazine incorporation into eggs, vitellogenin wa s separated from the hemolymph on native-PAGE and incubated with [C-14]lcyr omazine. A Sephadex G-25 gel filtration of the incubation mixture resolved two radioactive peaks. A major peal; was associated with the protein fracti on and a minor one corresponded to the free cyromazine fraction. It is like ly that cyromazine in the female hemolymph was bound to vitellogenin and in corporated into eggs. (C) 2001 Academic Press.