Regulation of ecdysteroidogenesis in prothoracic glands of the tobacco hornworm Manduca sexta.
Regulation of ecdysteroidogenesis in prothoracic glands of the tobacco hornworm Manduca sexta.
复制标题
烟草天蛾 Manduca sexta 前胸腺蜕皮类固醇生成的调节。
DOI：
10.1002/jez.1402520308
复制
发表时间：
1989
期刊：
影响因子：
--
通讯作者：
Bollenbacher,WE
中科院分区：
文献类型：
--
作者：
Watson,RD;Thomas,MK;Bollenbacher,WE
天蛾（Manduca sextaporthoracic glands）的蜕皮激素合成受一系列生物调节分子的调控，包括促前胸腺激素（PTTH）和幼虫血淋巴中的蛋白因子，以及腺体对这些分子的反应能力。粗PTTH、大PTTH和小PTTH各自在头部结扎的幼虫中引起幼虫蜕皮。然而，大PTTH的效力是粗PTTH的10倍，而粗PTTH的效力又比小PTTH高出几个数量级。当大、小PTTH组合时，蜕皮反应与粗PTTH相似。将[3 H]胆固醇注射到末龄幼虫中，并通过凝胶过滤色谱法分离放射性标记的血淋巴，结果显示有三个放射性峰。在含有血淋巴蛋白因子的组分中洗脱出一个峰，这一结果与该因子转运固醇底物的观点一致。通过评估该因子对前胸腺条件培养基中RIA可检测蜕皮类固醇蓄积的影响，研究了该因子为3（2）-酮还原酶的可能性。五个制剂的因素显着增强RIA可检测的蜕皮激素在条件培养基中的量，表明至少有一些制剂的因素可能含有ketoreductase activity.The上述研究结果进行了讨论的背景下，目前的假设生物调节分子如何与前胸腺相互作用，以调节ecdysteroidogenesis inManduca。
Ecdysteroidogenesis inManduca sextaprothoracic glands is regulated by a set of bioregulatory molecules, including prothoracicotropic hormone (PTTH) and a protein factor present in larval hemolymph, and by the competence of the glands to synthesize ecdysteroids in response to those molecules.A larval molting bioassay was used to assess the in vivo activity ofManducaPTTHs. Crude PTTH, big PTTH, and small PTTH each elicited a larval molt in head‐ligated larvae. However, big PTTH was ∽10‐fold more potent than crude PTTH, which was, in turn, several orders of magnitude more potent than small PTTH. When big and small PTTH were combined, the molting response was similar to that elicited with crude PTTH.The chemical nature of the hemolymph protein factor was also investigated. Injection of [3H]cholesterol into last‐instar larvae and fractionation of the radiolabeled hemolymph by gel filtration chromatography revealed three peaks of radioactivity. One peak eluted in fractions containing the hemolymph protein factor, a result consistent with the notion that the factor transports a sterol substrate. The possibility that the factor is a 3(2)‐ketoreductase was investigated by assessing the effect of the factor on the accumulation of RIA‐detectable ecdysteroids in prothoracic‐gland‐conditioned medium. Three of five preparations of the factor significantly enhanced the amount of RIA‐detectable ecdysteroids in conditioned medium, indicating that at least some preparations of the factor may contain ketoreductase activity.The above findings are discussed in the context of current hypotheses of how bioregulatory molecules interact with the prothoracic glands to regulate ecdysteroidogenesis inManduca.