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Effects of RH‐5992 on ecdysteroidogenesis of the prothoracic glands during the fourth larval instar of the silkworm, Bombyx mori
Author(s) -
Gu ShiHong,
Lin JuLing,
Lin PeiLing,
Kou Rong,
Smagghe Guy
Publication year - 2008
Publication title -
archives of insect biochemistry and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.576
H-Index - 66
eISSN - 1520-6327
pISSN - 0739-4462
DOI - 10.1002/arch.20262
Subject(s) - prothoracic gland , ecdysteroid , biology , medicine , endocrinology , hemolymph , bombyx mori , metamorphosis , bombyx , instar , western blot , ecdysone , larva , biochemistry , botany , hormone , gene
Stage‐dependent effects of RH‐5992 on ecdysteroidogenesis of the prothoracic glands during the fourth larval instar of the silkworm, Bombyx mori , were studied in the present report. When larvae were treated with RH‐5992 during the early stages of the fourth larval instar (between day 0 and day 1), initially ecdysteroid levels in the hemolymph were inhibited. However, 24 h after RH‐5992 application, ecdysteroid levels were greatly increased as compared with those treated with acetone. The examination of the in vitro prothoracic gland activity upon RH‐5992 application during the early stages of the fourth larval instar confirmed a short‐term inhibitory effect. When RH‐5992 was applied to the later stages of the fourth larval instar, no effects on both hemolymph ecdysteroid levels and prothoracic gland activity were observed. Addition of RH‐5992 to incubation medium strongly inhibited ecdysteroid secretion by the prothoracic glands from the early fourth instar, indicating direct action of RH‐5992 on ecdysteroidogenesis by prothoracic glands. Four hours after application with RH‐5992 on day 1.5, prothoracic glands still showed an activated response to PTTH in both PTTH‐cAMP signaling and the extracellular signal‐regulated kinase (ERK) signaling. Moreover, addition of RH‐5992 to incubation medium did not interfere with the stimulatory effect of the glands to PTTH in ecdysteroidogenesis. These results indicated that both PTTH‐cAMP signaling and PTTH‐ERK signaling may not be involved in short‐term inhibitory regulation by RH‐5992. Arch. Insect Biochem. Physiol. 68:197–205, 2008. © 2008 Wiley‐Liss, Inc.