EFFECT OF ECDYSTERONE ON VITELLOGENIN CONCENTRATION IN HAEMOLYMPH OF MALE AND FEMALE SARCOPHAGA BULLATA

Using Polyacrylamide gel electrophoresis, cycloheximide, incorporation of ³H-labelled amino acids and immunological methods, we have demonstrated that injection of ecdy- sterone induces de novo synthesis and release of vitellogenin in both sexes of Sarcophaga bullata. Vitellogenin concentrations were measured by the Mancini-radial immunodiffusion technique. In males a dose as low as 1 ng always makes vitellogenin appear in the haemolymph but very reproducible results are only obtained when doses varying from 10 to 250 ng were injected. In this range, the dose-response curve was linear on a semi- logarithmic scale.

In females, vitellogenin concentration remained low until a few hours after liver feeding and thereafter it rose sharply and reached its maximum about 24 h after the protein meal. 100 μg 6-hydroxydopamine HCl, injected before liver feeding in 4-day-old females, inhibited vitellogenin synthesis and yolk deposition, probably by interfering with the release of a brain hormone. This inhibitory effect on vitellogenin synthesis, but not that on yolk deposition, could be overruled by injection of ecdysterone. Juvenile hormone was ineffective on both. Females, ovariectomized on day 2 or 3, accumulated vitellogenin in their haemolymph, indicating that the continuous presence of the ovaries was not required for vitellogenin synthesis. The possible relation between the gonadotrophs hormone from the brain, vitellogenin synthesis and moulting hormone metabolism is discussed.