Ecdysteroid biosynthesis in crayfish Y-organs: Feedback regulation by circulating ecdysteroids

✍ Scribed by Susanne Dell; Dietrich Sedlmeier; Detlef Böcking; Chantal Dauphin-Villemant

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 147 KB
• Volume: 41
• Category: Article
• ISSN: 0739-4462
• DOI: 10.1002/(sici)1520-6327(1999)41:3<148::aid-arch6>3.0.co;2-u

✦ Synopsis

In crustaceans, ecdysteroid synthesis in the Y-organs is negatively regulated by the molt-inhibiting hormone (MIH). Reduction or cessation of MIH release from the sinus gland in the eyestalk, probably due to environmental cues, is one of possibly several signals for an increase of edysteroid production and subsequently enhancement of 20-hydroxyecdysone (20E) levels in the hemolymph. The present study asks the question whether the 20E peak in premoult stages D 2 /D 3 is explained solely by the cessation of MIH release or whether positive feedback mechanisms are also involved. Ecdysteroid production by the Y-organ of the crayfish Orconectes limosus was found to be under negative feedback control by circulating ecdysteroids. Exogenous 20-hydroxyecdysone (20E) as well as RH-5849, a nonsteroidal ecdysteroid agonist, reduced ecdysteroid synthesis significantly when injected into intermoult animals. A direct, short loop inhibitory feedback effect was demonstrated by in vitro incubations of Y-organs with RH-5849. Thus, the results presented here do not point to a stimulatory effect of 20E on Yorgan activity but suggest that during intermolt a negative feedback by ecdysteroids plays a role in addition to MIH. Arch.