Evidence for the presence of makisterone A in Drosophila larvae and the secretion of 20-deoxymakisterone A by the ring gland

摘要

Ring glands or brain—ring gland complexes from third-instar Drosophila melanogaster larvae secreted ecdysone [(22R)-2β,3β,14α,22,25-pentahydroxy-5β-cholest-7-en-6-one] and two less polar ecdysteroids (LP1 and LP2) in vitro. Radioimmunoassay with different antisera indicated that LP1 and LP2 are side-chain-modified analogues of ecdysone. In high-performance liquid chromatography, the retention time of LP2 was equivalent to that of a precursor of makisterone A [(20R,22R)-2β,3β,14α,20,22,25-hexahydroxy-24-methyl-5β-cholest-7-en-6-one] secreted by Dysdercus fasciatus prothoracic glands in vitro. LP2 was metabolized in vitro by the fat body of Drosophila larvae to a product with the characteristics of makisterone A when analyzed by gas chromatography/mass spectrometry (selected ion monitoring). Evidence was obtained for the presence of makisterone A in Drosophila larvae. These data suggest that LP2 is 20-deoxymakisterone A (24-methylecdysone) and that makisterone A could function as an additional moulting hormone in Drosophila, although 20-deoxymakisterone A production is apparently dependent on the sterol composition of the diet. LP1 has not been identified.