The distribution of ecdysone metabolites within the body of adult Drosophila melanogaster females and their sites of production

Abstract

[ 3H]Ecdysone was injected into adult female Drosophila melanogaster and the distribution of the metabolites within the body was investigated after incubation times of 2–3 and 4–5 h at room temperature. Most of the radioactivity retained within the body was detected in the gut and haemolymph. Almost all metabolites found in the gut were ecdysone 22-fatty acid acyl esters; in the haemolymph almost all the metabolites detected in whole flies were also present. In the ovaries the metabolite pattern was very complex as well. At 4–5 h after the injection of [ 3H]ecdysone polar anionic (weakly acidic) conjugates of 20-hydroxyecdysone and another metabolite of ecdysone were restricted to the ovaries. 20-Hydroxyecdysone was detected in the ovaries and haemolymph. In a second experiment the contribution of different tissues of the body to the metabolism of ecdysone was studied in vitro. Polar metabolites of ecdysone, which were found in the ovaries, were produced at least in small amounts by the ovaries themselves. Ecdysone was efficiently converted to 3-dehydroecdysone and ecdysone 22-fatty acid acyl esters by gut/malpighian tubule complexes, the most probable source of these compounds found in the ovaries and faeces.