Watson R D, Bollenbacher W E
Department of Biology, University of North Carolina, Chapel Hill 27599-3280.
Mol Cell Endocrinol. 1988 Jun;57(3):251-9. doi: 10.1016/0303-7207(88)90081-0.
The acquisition of steroidogenic competence by prothoracic glands of last instar Manduca sexta larvae is regulated by juvenile hormone (JH). Topical treatment of pre-commitment larvae with JH I or (7S)-hydroprene (a JH analog) delays development by increasing the time to pupal commitment and wandering. Prothoracic gland competence is suppressed in JH-treated larvae: Unstimulated and prothoracicotropic hormone (PTTH)-stimulated rates of in vitro ecdysone secretion are decreased relative to rates of secretion by competent glands. (7S)-Hydroprene also suppresses the competence of glands in head-ligated pre-commitment larvae, suggesting the hormone acts directly on the glands. Two results indicate PTTH plays a role in controlling competence, and that JH regulates competence indirectly by inhibiting PTTH release: (1) head-ligation prevents the acquisition of full competence, and (2) cAMP levels are elevated in glands from JH-treated larvae. Thus, the decrease in the JH titer that precedes pupal commitment in Manduca is permissive for the acquisition by prothoracic glands of steroidogenic competence.
末龄烟草天蛾幼虫前胸腺获得类固醇生成能力受保幼激素（JH）调控。用JH I或（7S）-烯虫酯（一种JH类似物）对处于预变态期的幼虫进行局部处理，会通过延长进入蛹期和化蛹的时间来延缓发育。在经JH处理的幼虫中，前胸腺的能力受到抑制：相对于有能力的腺体，未受刺激以及促前胸腺激素（PTTH）刺激的体外蜕皮激素分泌速率均降低。（7S）-烯虫酯也会抑制头部结扎的预变态期幼虫腺体的能力，这表明该激素直接作用于腺体。有两个结果表明PTTH在控制能力方面发挥作用，且JH通过抑制PTTH释放间接调节能力：（1）头部结扎会阻止完全获得能力；（2）经JH处理的幼虫腺体中的cAMP水平升高。因此，烟草天蛾在进入蛹期前JH滴度的下降有利于前胸腺获得类固醇生成能力。
