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Proceedings of the National Academy of Sciences of the United States of America logoLink to Proceedings of the National Academy of Sciences of the United States of America
. 1988 Feb;85(3):958–962. doi: 10.1073/pnas.85.3.958

Regulation of the ecdysteroid titer of Manduca sexta: reappraisal of the role of the prothoracic glands.

J T Warren 1, S Sakurai 1, D B Rountree 1, L I Gilbert 1, S S Lee 1, K Nakanishi 1
PMCID: PMC365795  PMID: 3422473

Abstract

It is generally accepted that the prothoracic glands of insects produce ecdysone, which is converted by a 20-monooxygenase in peripheral tissues to the major molting hormone, 20-hydroxyecdysone. Incubation in vitro of the prothoracic glands of larval or pupal Manduca sexta in the presence of a hemolymph protein fraction (HPF) increased the ecdysteroid content of the medium almost 8-fold. A comparable increase was noted when HPF was added to medium preconditioned with prothoracic glands but from which the glands had been removed. We used a differential RIA to show that a major product of the prothoracic glands in vitro cross-reacts with antiserum (20-hydroxyecdysone-2-succinylthyroglobulin amide; H-2) that retains affinity to ecdysteroids having a modified A ring. However, this product did not bind to antiserum (ecdysone-22-succinylthyroglobulin amide; H-22) that has affinity mainly for ecdysteroids modified at the side chain. We employed radiolabeled precursor studies with prothoracic glands in vitro and a combination of analytical techniques (NMR, CD, MS) to demonstrate that the major ecdysteroid release from the glands is a mixture of 2-dehydroecdysone and 3-dehydroecdysone (1:2), which is rapidly reduced to ecdysone in the presence of HPF. We postulate that the active component of HPF is 3 beta 3 beta (2 beta)-formin-3(2)-ketoecdysteroid reductase. These results may explain several anomalous observations pertaining to the molting of insect fragments in the absence of prothoracic glands and suggest a complex system for the control of insect molting and metamorphosis.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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