Metabolism of some possible ecdysone precursors in Calliphora stygia

Abstract A study has been made, using Calliphora stygia at the time of puparium formation, of the incorporation of a number of labelled sterols into β -ecdysone. [1 α - 3 H]-Cholesterol and [4- 14 C]-cholesterol are incorporated to a similar extent (0·01-0·02%). [1- 3 H]-7-Dehydrocholesterol is better incorporated (0·025%) than cholesterol while [1 α - 3 H]-cholesterol sulphate, (22R)-22-hydroxy-[22- 3 H]-cholesterol, and 25-hydroxy-[26- 14 C]-cholesterol are not incorporated to a significant extent.