title: Involvement of microtubules in prothoracicotropic hormone-stimulated ecdysteroidogenesis by insect (Manduca sexta) prothoracic glands.
abstract: Secretion of ecdysteroid molting hormones by insect prothoracic glands is stimulated by neuropeptide prothoracicotropic hormones (PTTH). Studies reported here were conducted to assess the effects of microfilament and microtubule inhibitors on in vitro ecdysteroidogenesis by prothoracic glands of Manduca sexta. Microfilament inhibitors (cytochalasins B and D) had no effect on basal or big PTTH-stimulated ecdysteroidogenesis. Microtubule inhibitors (colchicine, podophyllotoxin, nocodazole) had no effect on basal ecdysteroid secretion, but suppressed PTTH-stimulated secretion in a concentration-dependent manner. The effect of nocodazole was partially reversible, suggesting it was not due to nonspecific toxicity. Colchicine had no effect on glandular ecdysteroid levels, indicating that inhibition was not due solely to blockage of secretion. The combined results are consistent with the hypothesis that microtubule-mediated transport of ecdysteroid precursors plays a critical role in stimulation of ecdysteroidogenesis by PTTH.
authors.affiliation: Department of Biology, University of Alabama at Birmingham 35294, USA.
authors.forename: R D
authors.initials: RD
authors.lastname: Watson
authors.forename: S
authors.initials: S
authors.lastname: Ackerman-Morris
authors.forename: W A
authors.initials: WA
authors.lastname: Smith
authors.forename: C J
authors.initials: CJ
authors.lastname: Watson
authors.forename: W E
authors.initials: WE
authors.lastname: Bollenbacher
mesh_terms: D008841:Actin Cytoskeleton / Q000187:drug effects / Q000502:physiology; D000818:Animals; D003078:Colchicine / Q000494:pharmacology; D003571:Cytochalasin B / Q000494:pharmacology; D015638:Cytochalasin D / Q000494:pharmacology; D026461:Ecdysteroids; D004702:Endocrine Glands / Q000187:drug effects / Q000378:metabolism; D066298:In Vitro Techniques; D007301:Insect Hormones / Q000096:biosynthesis* / Q000494:pharmacology*; D018402:Manduca / Q000378:metabolism*; D008870:Microtubules / Q000187:drug effects / Q000502:physiology*; D015739:Nocodazole / Q000494:pharmacology; D011034:Podophyllotoxin / Q000494:pharmacology; D013256:Steroids / Q000096:biosynthesis*
chemical_list: D026461:Ecdysteroids; D007301:Insect Hormones; D013256:Steroids; D015638:Cytochalasin D; D003571:Cytochalasin B; C009089:prothoracicotropic hormone; D011034:Podophyllotoxin; D015739:Nocodazole; D003078:Colchicine