Barry T P, Ochiai M, Malison J A
University of Wisconsin Aquaculture Program, Department of Food Science, Madison 53706, USA.
Gen Comp Endocrinol. 1995 Sep;99(3):382-7. doi: 10.1006/gcen.1995.1122.
Interrenal tissue from embryonic and larval rainbow trout (Oncorhynchus mykiss) was cultured in vitro and exposed to various doses of adrenocorticotropin (ACTH) to document the ontogeny of interrenal responsiveness to tropic stimulation. Resting and acute stress-induced changes in whole-body cortisol levels in vivo were also measured to determine if the corticosteroid stress response first develops with the onset of interrenal responsiveness to ACTH. No evidence was found that the hypothalamic-pituitary-interrenal (HPI) axis of rainbow trout is transiently activated prior to hatching. In vivo, a corticosteroid stress response was first observed 2 weeks after hatching, and stress-induced cortisol levels (at 1 hr poststress) were significantly higher 3 weeks after hatching than they were at 2 or 4 weeks after hatching. In contrast, cultured interrenal tissue produced significant levels of cortisol in response to ACTH at the time of hatching, and in vitro cortisol production by the interrenal increased significantly between 3 and 4 weeks after hatching. Interrenal sensitivity to ACTH did not change appreciably with development. We conclude that (1) the final maturation of the corticosteroid stress response in rainbow trout occurs at the level of the brain and/or sensory inputs and not at the level of the interrenal cell; (2) negative feedback mechanisms within the HPI axis develop 3 to 4 weeks after hatching; and (3) the period between 3 and 4 weeks after hatching may be homologous to the stress hyporesponsive period after birth in mammals and thus could be a stage when environmental influences can permanently alter the development of the corticosteroid stress response in rainbow trout.
对胚胎期和幼体期虹鳟（Oncorhynchus mykiss）的肾上腺组织进行体外培养，并使其暴露于不同剂量的促肾上腺皮质激素（ACTH）下，以记录肾上腺对促激素刺激反应的个体发生过程。还测量了虹鳟在静息状态和急性应激诱导下体内全身皮质醇水平的变化，以确定皮质类固醇应激反应是否首先随着肾上腺对ACTH反应的开始而发展。未发现有证据表明虹鳟的下丘脑 - 垂体 - 肾上腺（HPI）轴在孵化前会短暂激活。在体内，孵化后2周首次观察到皮质类固醇应激反应，应激诱导的皮质醇水平（应激后1小时）在孵化后3周显著高于孵化后2周或4周时的水平。相比之下，培养的肾上腺组织在孵化时就能对ACTH产生显著水平的皮质醇，并且肾上腺在体外产生的皮质醇在孵化后3至4周之间显著增加。肾上腺对ACTH的敏感性并未随着发育而明显变化。我们得出以下结论：（1）虹鳟皮质类固醇应激反应的最终成熟发生在大脑和/或感觉输入水平，而非肾上腺细胞水平；（2）HPI轴内的负反馈机制在孵化后3至4周发育；（3）孵化后3至4周的时间段可能与哺乳动物出生后的应激低反应期同源，因此可能是一个环境影响可永久改变虹鳟皮质类固醇应激反应发育的阶段。
