Balm P H, Pepels P, Helfrich S, Hovens M L, Bonga S E
Department of Animal Physiology, Faculty of Science, University of Nijmegen, The Netherlands.
Gen Comp Endocrinol. 1994 Dec;96(3):347-60. doi: 10.1006/gcen.1994.1190.
This study examines ACTH-like immunoreactivity in the pituitary pars distalis and pars intermedia of the freshwater teleost Oreochromis mossambicus (tilapia). Two products (tACTHA and tACTHB) were present in both lobes. These two products also accounted for the majority of the ACTH i.r. when in vitro pars distalis incubation medium was analyzed by HPLC. In a homologous bioassay the two tilapia ACTH-like molecules and human ACTH1-39 possessed similar corticotropic potency. The peptides were quantified using a newly validated radioimmunoassay, which was also used to measure ACTH in plasma of unstressed and stressed fish. Short-term (< 12 min) stress rapidly increased plasma cortisol, reaching levels of around 300 ng/ml in 5 min. Surprisingly, this initial elevation was not accompanied by a rise in plasma ACTH levels. A more prolonged (3 hr) confinement in pairs resulted in high plasma cortisol and ACTH levels in one fish of every pair. The second fish had control ACTH levels and only marginally elevated cortisol levels. Therefore, in this species social interactions seem to influence the reaction of the pituitary-interrenal axis to stress. The short-term cortisol response to disturbance could be abolished completely by pretreating fish in vivo with cortisol for 48 hr. This treatment did not alter circulating ACTH levels. It is concluded that tilapia did not rely on circulating ACTH for a rapid elevation of plasma cortisol levels. Both neuronal mechanisms and cortisol feedback may regulate the pituitary-interrenal axis at the level of the interrenal.
本研究检测了淡水硬骨鱼莫桑比克罗非鱼（罗非鱼）垂体远侧部和中间部中促肾上腺皮质激素（ACTH）样免疫反应性。两个叶中均存在两种产物（tACTHA和tACTHB）。当通过高效液相色谱法分析体外远侧部孵育培养基时，这两种产物也占ACTH免疫反应性的大部分。在同源生物测定中，两种罗非鱼ACTH样分子和人ACTH1-39具有相似的促肾上腺皮质激素活性。使用一种新验证的放射免疫测定法定量这些肽，该方法也用于测量未受应激和受应激鱼血浆中的ACTH。短期（<12分钟）应激迅速增加血浆皮质醇，5分钟内达到约300 ng/ml的水平。令人惊讶的是，这种初始升高并未伴随着血浆ACTH水平的升高。更长期（3小时）的成对饲养导致每对鱼中的一条鱼血浆皮质醇和ACTH水平升高。第二条鱼的ACTH水平处于对照水平，皮质醇水平仅略有升高。因此，在该物种中，社会互动似乎会影响垂体-肾间轴对应激的反应。通过在体内用皮质醇预处理鱼48小时，可完全消除对干扰的短期皮质醇反应。这种处理并未改变循环ACTH水平。得出的结论是，罗非鱼在血浆皮质醇水平快速升高时并不依赖循环ACTH。神经元机制和皮质醇反馈可能在肾间水平调节垂体-肾间轴。
