Light is an essential factor for organisms and affects the endocrine and stress regulation of fish in nature. However, sudden changes in light and dark conditions in artificial environments can negatively impact fish. In the present study, to evaluate the physiological and oxidative stress responses of goldfish (Carassius auratus) exposed to two different light conditions, sudden light changes and slowly dimming light changes for 24 h, we analyzed the mRNA expression and activity of stress indicators [corticotropin-releasing hormone (CRH) and pro–opiomelanocortin (POMC)], levels of plasma cortisol and glucose, mRNA expression of glucocorticoid receptor (GR), and activity of plasma oxidative stress indicators (superoxide dismutase and catalase). Consequently, the mRNA expressions and activities of CRH and POMC, plasma levels of cortisol and glucose, and mRNA expression of GR were found to be significantly increased during the light changes, particularly in the control group. Additionally, plasma levels of cortisol and glucose in the control group were significantly higher than those in the dimming group during the light changes. However, no significant differences in mRNA expression levels and activities of antioxidant enzymes both in the control and dimming groups were observed. These results indicate that dimming light induces less stress than sudden changes in light.

光线是生物体的重要因素，会影响自然界鱼类的内分泌和压力调节。但是，人造环境中明暗条件的突然变化可能会对鱼类造成负面影响。在本研究中，评估金鱼（（鱼）的生理和氧化应激反应）暴露于两种不同的光照条件下，即突然的光线变化和缓慢的光线变化持续24 h，我们分析了应激指标[促肾上腺皮质激素释放激素（CRH）和促-opiomelanocortin（POMC）]的mRNA表达和活性，血浆水平皮质醇和葡萄糖，糖皮质激素受体（GR）的mRNA表达以及血浆氧化应激指标（超氧化物歧化酶和过氧化氢酶）的活性。因此，发现在光照变化期间，CRH和POMC的mRNA表达和活性，血浆皮质醇和葡萄糖水平以及GR的mRNA表达显着增加，特别是在对照组中。另外，在光变化过程中，对照组的血浆皮质醇和葡萄糖水平显着高于调光组。然而，在对照组和调光组中，均未观察到mRNA表达水平和抗氧化酶活性的显着差异。这些结果表明，调暗光所引起的压力要比光的突然变化小。