Metabolism of some possible ecdysone precursors in Calliphora stygia

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. [1α-3H]-Cholesterol and [4-14C]-cholesterol are incorporated to a similar extent (0·01-0·02%). [1-3H]-7-Dehydrocholesterol is better incorporated (0·025%) than cholesterol while [1α-3H]-cholesterol sulphate, (22R)-22-hydroxy-[22-3H]-cholesterol, and 25-hydroxy-[26-14C]-cholesterol are not incorporated to a significant extent.