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

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 product...

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Bibliographic Details
Published in:Archives of insect biochemistry and physiology 1999, Vol.41 (3), p.148-155
Main Authors: Dell, S, Sedlmeier, D, Bocking, D, Dauphin-Villemant, C
Format: Article
Language:English
Subjects:
20E
agonists
animal glands
biosynthesis
crayfish
Crustacea
dose response
ecdysteroid synthesis
ecdysteroids
ecdysterone
feedback
feedback regulation
inhibition
injection
Orconectes
orconectes limosus
regulation
RH-5849
Y-organ
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Summary: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 D2/D3 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 Y-organ activity but suggest that during intermolt a negative feedback by ecdysteroids plays a role in addition to MIH.
ISSN:0739-4462
1520-6327
DOI:10.1002/(SICI)1520-6327(1999)41:3<148::AID-ARCH6>3.0.CO;2-U