Lattin Christine R, Romero L Michael
Department of Biology, Tufts University, Medford, MA 02155, USA
Department of Biology, Tufts University, Medford, MA 02155, USA.
J Exp Biol. 2014 Jul 15;217(Pt 14):2601-8. doi: 10.1242/jeb.103788. Epub 2014 May 6.
The physiological stress response results in release of glucocorticoid hormones such as corticosterone (CORT). Whereas short-term activation of this response helps animals cope with environmental stressors, chronic activation can result in negative effects including metabolic dysregulation and reproductive failure. However, there is no consensus hormonal profile of a chronically stressed animal, suggesting that researchers may need to look beyond hormone titers to interpret the impacts of chronic stress. In this study, we brought wild house sparrows (Passer domesticus) into captivity. We then compared glucocorticoid and mineralocorticoid receptor concentrations in sparrows exposed either to a standardized chronic stress protocol (n=26) or to standard husbandry conditions (controls; n=20). We used radioligand binding assays to quantify receptors in whole brain, liver, kidneys, spleen, gonads, gastrocnemius and pectoralis muscle, omental and subcutaneous fat, and bib and back skin. In most tissues, CORT receptors did not differ between controls and stressed animals, although we found marginal increases in receptor density in kidney and testes in stressed birds at some time points. Only in pectoralis muscle was there a robust effect of chronic stress, with both receptor types higher in stressed animals. Increased pectoralis sensitivity to CORT with chronic stress may be part of the underlying mechanism for muscle wasting in animals administered exogenous CORT. Furthermore, the change in pectoralis was not paralleled by gastrocnemius receptors. This difference may help explain previous reports of a greater effect of CORT on pectoralis than on other muscle types, and indicate that birds use this muscle as a protein reserve.
生理应激反应会导致糖皮质激素如皮质酮（CORT）的释放。虽然这种反应的短期激活有助于动物应对环境应激源，但长期激活可能会产生负面影响，包括代谢失调和生殖功能衰竭。然而，对于长期应激动物的激素特征尚无共识，这表明研究人员可能需要超越激素水平来解释慢性应激的影响。在本研究中，我们将野生家麻雀（Passer domesticus）圈养起来。然后，我们比较了暴露于标准化慢性应激方案（n = 26）或标准饲养条件（对照组；n = 20）下的麻雀体内糖皮质激素和盐皮质激素受体的浓度。我们使用放射性配体结合测定法来量化全脑、肝脏、肾脏、脾脏、性腺、腓肠肌和胸肌、网膜和皮下脂肪以及喉部和背部皮肤中的受体。在大多数组织中，对照组和应激动物之间的CORT受体没有差异，尽管我们发现在某些时间点，应激鸟类的肾脏和睾丸中的受体密度略有增加。只有胸肌出现了慢性应激的显著影响，应激动物体内两种受体类型的含量都更高。慢性应激导致胸肌对CORT的敏感性增加，这可能是外源性CORT处理的动物肌肉萎缩潜在机制的一部分。此外，腓肠肌受体的变化与胸肌不同。这种差异可能有助于解释先前关于CORT对胸肌的影响大于对其他肌肉类型的报道，并表明鸟类将这块肌肉用作蛋白质储备。
