Ismail S M, Ismail P M, Gillott C
Department of Biology, University of Saskatchewan, Saskatoon, Canada.
Gen Comp Endocrinol. 1995 Apr;98(1):87-93. doi: 10.1006/gcen.1995.1046.
Juvenile hormone (JH) regulation of the synthesis of LHPI, the major secretory protein of the long hyaline tubule in the male accessory reproductive gland (MARG) of Melanoplus sanguinipes, was examined by in vitro radiolabeling and immunoprecipitation. In MARG taken from normal insects JH III immediately stimulates production of immunospecific LHPI. In contrast, JH III does not initially promote synthesis of LHPI in MARG of allatectomized insects. Only after prior exposure to the hormone [for 24 hr when applied in vivo (topically) or 16 hr under in vitro conditions] is LHPI synthesis enhanced by JH III in the MARG of allatectomized insects. These results suggest that in the prolonged absence of JH III the MARG are "switched off," that is, lose their sensitivity to the hormone. Sensitivity is regained during the 24- or 16-hr "lag phase." Use of the translational inhibitor cycloheximide confirmed the existence of the lag phase in JH III-mediated LHPI synthesis. JH III stimulates RNA synthesis in a dose-dependent manner in the long hyaline tubule at concentrations < 64 nM. Above this level, RNA synthesis was depressed. Actinomycin D given simultaneously with JH III inhibited RNA synthesis, but not the synthesis of LHPI in the long hyaline tubule. It is suggested that understanding the nature of the lag phase will facilitate clarification of the mechanism of action of JH in the MARG.
通过体外放射性标记和免疫沉淀法，研究了保幼激素（JH）对红腿蝗雄性附属性腺（MARG）长透明小管主要分泌蛋白LHPI合成的调节作用。从正常昆虫获取的MARG中，JH III可立即刺激免疫特异性LHPI的产生。相比之下，JH III最初并不会促进去腺体昆虫MARG中LHPI的合成。只有在预先接触该激素后（体内局部应用24小时或体外条件下16小时），JH III才能增强去腺体昆虫MARG中LHPI的合成。这些结果表明，在长期缺乏JH III的情况下，MARG处于“关闭”状态，即失去了对该激素的敏感性。在24或16小时的“滞后阶段”，敏感性得以恢复。使用翻译抑制剂环己酰亚胺证实了JH III介导的LHPI合成中存在滞后阶段。在浓度<64 nM时，JH III以剂量依赖的方式刺激长透明小管中的RNA合成。高于此水平，RNA合成受到抑制。与JH III同时给予放线菌素D可抑制RNA合成，但不影响长透明小管中LHPI的合成。研究表明，了解滞后阶段的本质将有助于阐明JH在MARG中的作用机制。
