Biosynthesis of ecdysteroids from cholesterol by crab Y-organs, and eyestalk suppression of cholesterol uptake and secretory activity, in vitro.
Precursor incorporation studies were conducted in vitro with activated Y-organs from 48-hr de-eyestalked Cancer antennarius donors. When the glands were prelabeled in vivo by systemic injection of [3H]cholesterol 12 hr prior to removal, and subsequently incubated 24 hr in label-free medium, the glands secreted 3H-labeled ecdysone. The glands also secreted an unidentified ecdysteroid with comigrating 3H-label with characteristic retention time on normal-phase HPLC of 4 min (4-min unknown). The compound is less polar, and is secreted in a quantity and apparent specific activity approximately fivefold greater, than ecdysone. Compared with chromatographic retention times and competitive binding curves of authentic standards, the 4-min unknown was determined not to be ponasterone A, inokosterone, makisterone, or several other possible products or intermediates. In contrast with Y-organs from intact donors, those from de-eyestalked crabs exhibit greatly increased cholesterol uptake and secretion of both ecdysone and 4-min unknown in vitro. All three responses were suppressed in dose-dependent manner by eyestalk extract in the dose range, 1-4 eyestalk equivalents/Y-organ. Secretion of 4-min unknown was the response most sensitive to eyestalk extract (requiring the least dose for 50% inhibition).
D000818:Animals; D001667:Binding, Competitive; D003386:Brachyura / Q000378:metabolism*; D002784:Cholesterol / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D002855:Chromatography, Thin Layer; D004440:Ecdysone / Q000378:metabolism; D026461:Ecdysteroids; D007447:Invertebrate Hormones / Q000096:biosynthesis* / Q000378:metabolism; D009799:Ocular Physiological Phenomena; D009924:Organ Culture Techniques
D026461:Ecdysteroids; D007447:Invertebrate Hormones; D004440:Ecdysone; D002784:Cholesterol