Durant Sarah E, Romero L Michael, Talent Larry G, Hopkins William A
Wildlife Ecotoxicology and Physiological Ecology Program, Department of Fisheries and Wildlife Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA.
Gen Comp Endocrinol. 2008 Mar 1;156(1):126-33. doi: 10.1016/j.ygcen.2007.12.004. Epub 2008 Feb 4.
Release of glucocorticoids (GCs) enables organisms to meet energy requirements during stressful situations by regulating intermediary metabolism. In the absence of compensatory mechanisms, increased metabolic activity (e.g., protein catabolism, lipolysis, and gluconeogenesis) should translate to increases in whole animal metabolism, and therefore energy expenditures, by organisms. However, to our knowledge, no study has estimated the total energy cost of elevated plasma GCs in any organism. Here we evaluated the effect of exogenous corticosterone (CORT) on metabolism in captive western fence lizards (Sceloporus occidentalis) by conducting two experiments. In experiment I we determined the dynamics of plasma CORT concentrations resulting from CORT injections. In experiment II we frequently measured changes in respiration for 24h before and after CORT injection. Injection of 0.025 microg/g (low CORT) and 0.40 microg/g CORT (high CORT) produced up to 26-fold increases in plasma CORT in lizards 3h following injection compared to baseline levels. Plasma CORT concentrations returned to baseline levels 6h after injection. CORT increased metabolism in both low and high CORT lizards (up to 121% and 245%, respectively) during the first 7.5h after CORT injections compared to pre-treatment trials. Respiration returned to baseline rates 7.5h after CORT administration. A surprising finding was that although high CORT males achieved higher plasma CORT concentrations than high CORT females, the metabolic response of high CORT females was 30% greater than high CORT males. Our results suggest that GC-induced changes in respiration may be important for understanding the overall energetic implications of stress.
糖皮质激素（GCs）的释放使生物体能够通过调节中间代谢来满足应激状态下的能量需求。在没有代偿机制的情况下，代谢活动增加（如蛋白质分解代谢、脂肪分解和糖异生）应会导致整个动物代谢增加，进而使生物体的能量消耗增加。然而，据我们所知，尚无研究估算过任何生物体血浆GCs升高的总能量成本。在此，我们通过两项实验评估了外源性皮质酮（CORT）对圈养西部围栏蜥蜴（Sceloporus occidentalis）代谢的影响。在实验I中，我们测定了注射CORT后血浆CORT浓度的动态变化。在实验II中，我们在注射CORT前后24小时频繁测量呼吸变化。与基线水平相比，注射0.025微克/克（低剂量CORT）和0.40微克/克CORT（高剂量CORT）后3小时，蜥蜴血浆CORT浓度最多增加了26倍。注射后6小时，血浆CORT浓度恢复到基线水平。与预处理试验相比，在注射CORT后的前7.5小时内，低剂量和高剂量CORT蜥蜴的代谢均增加（分别高达126%和245%）。注射CORT后7.5小时，呼吸恢复到基线速率。一个惊人的发现是，尽管高剂量CORT雄性蜥蜴的血浆CORT浓度高于高剂量CORT雌性蜥蜴，但高剂量CORT雌性蜥蜴的代谢反应比高剂量CORT雄性蜥蜴大30%。我们的结果表明，GC诱导的呼吸变化可能对于理解应激的整体能量影响很重要。
