Ecdysteroid synthesis by crab Y‐organs

Abstract

Abstract Y‐organs of the crab Carcinus maenas synthesize two ecdysteroids—ecdysone and 25‐deoxyecdysone—which are the precursors of 20‐hydroxyecdysone and ponasterone A, respectively; 25‐deoxyecdysone was detected by using two methods: (1) radiolabeled cholesterol injection into premolt crabs, followed by in vitro incubation of their Y‐organs and high‐performance liquid chromatography (HPLC) analysis of the various ecdysteroids formed, and 2) identification of ecdysteroids secreted by incubated crab Y‐organs by means of two successive HPLC purifications, followed by radioimmunoassay (RIA) and mass spectrum analysis. The only sterols found in the Y‐organs are 7‐dehydrocholesterol and cholesterol. These are probably the ecdysone and 25‐deoxyecdysone precursors. The biological activity of 25‐deoxyecdysone, tested by its induction of the transcription of gene P1 in Drosophila fat body, was the same as that of 20‐hydroxyecdysone.