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

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Abstract
Ring glands or brain-ring gland complexes from 3rd-instar D. melanogaster larvae secreted ecdysone [(22R)-2.beta., 3.beta., 14.alpha., 22, 25-pentahydroxy-5.beta.-cholest-7-en-6-one] and 2 less polar ecdysteroids (LP1 and LP2) in vitro. Radioimmunoassay with different antisera indicated that LP1 and LP2 are side-chain-modified analogs of ecdysone. In high-performance liquid chromatography, the retention time of LP2 was equivalent to that of a precursor of makisterone A [(20R, 22R)-2.beta., 3.beta., 14.alpha., 20, 22, 25-hexahydroxy-24-methyl-5.beta.-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. LP2 apparently is 20-deoxymakisterone A (24-methylecdysone) and 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.