Inactivation of ecdysone and the possible feed back control of the titre during pupation of Sarcophaga peregrina

Abstract

Radioactive β-ecdysone injected into mature larvae or pharate pupae of Sarcophaga peregrina was rapidly metabolized, but the decrease in moulting hormone activity in whole animal extracts was much faster than the decrease of radioactivity. The metabolites were extracted, examined by TLC and HPLC and shown to be conjugates of β-ecdysone in larvae (as shown by enzymatic hydrolysis) but 3-epi-β-ecdysone in pupae. These compounds did not exhibit appreciable activity. The process of inactivation by epimerization may be a mechanism of feed back control of ecdysone, since epimerization is induced by ecdysone itself.