Implication des 3-déhydroecdystéroïdes dans la voie de biosynthèse de l'ecdysone chez Locusta migratoria, in vitro

Abstract

Prothoracic glands of the locust, Locusta migratoria, incubated in vitro converted tritiated 3-dehydrocetodiol (22,23,24,25 ³H₄-14α-hydroxy-5β-cholest-7-en-3,6-dione) into ecdysteroïds and 3-déhydroecdysteroïds as far as the final products of the two series, ecdysone and 3-dehydroecdysone. In the two series, the different compounds are formed in the same quantities, except for 2,22-desoxy-products, the nature of which could not have been determined. Converted 3-dehydroecdysone issued from 3-dehydrocetodiol is transformed into ecdysone after several hours incubation with Locusta last instar larvae hemolymph. Till now is has been impossible to determine if the reduction of 3-dehydroecdysteroïds took place into the prothoracic glands or in the incubation medium. In no case is 3-dehydrocetodiol converted into cetodiol. Conversion rates of the different compounds, either issued from cetodiol or from 3-dehydrocetodiol as precursors, are of same importance, so that a weak specificity of the hydroxylation enzymes must be considered.