Department of Biology, Section of Ecology, University of Turku, FI-20014 Turku, Finland.
Environ Res. 2011 Apr;111(3):362-70. doi: 10.1016/j.envres.2011.01.005. Epub 2011 Feb 4.
Metals can cause oxidative stress by increasing the formation of reactive oxygen species (ROS), when there are insufficient amount of antioxidants to defend against the growing amount of free radicals. We aimed to find out the most reliable biomarkers to detect pollution-related oxidative stress in wild birds by comparing oxidative stress status in great tit (Parus major) nestlings at populations in polluted and unpolluted areas. We also studied with experimental manipulations whether dietary carotenoid levels have any role in great tits' antioxidant defence and whether their carotenoid-based plumage colour was connected to an oxidative stress status. We used antioxidants (GSH, carotenoids) and several antioxidant enzymes (GP, GR, GST, SOD, and CAT) as indicators of the oxidative stress. We found no direct connections between dietary metal exposure and antioxidant or antioxidant enzyme levels. The activity of GP was, however, slightly higher in the polluted environment. This was due to poorer condition and subsequently higher level of oxidative stress in the nestlings in the polluted area. We also found a positive association between GP and an ambient temperature during the nestling period, which may be due to higher metabolic activity of partly poikilothermic nestlings in warm weather. The activity of GST was positively related to the number of nestlings at the sampling time. Fledging success was better in an unpolluted area, where also the nestling body mass was higher. Carotenoid treatment increased the plasma carotenoid concentrations 2.1 fold in carotenoid-supplemented birds, but was not associated with the oxidative stress biomarkers or metal levels. The yellow plumage colour was associated with dietary carotenoid levels in both study areas, but not with the metal exposure or the oxidative stress status. Our results suggest that at the exposure levels found in our study area, the enzyme activities do not indicate metal-related oxidative stress. Instead, GP can be used as an indicator of growth related oxidative stress, which is greater in the polluted area. The activity of this enzyme was, however, not directly related to metal exposure, but more likely to some secondary pollution-related change in the nestling condition.
金属会通过增加活性氧物质（ROS）的形成来引起氧化应激，当抗氧化剂的数量不足以抵御自由基的增加时。我们的目的是通过比较污染区和未污染区的大山雀（Parus major）雏鸟的氧化应激状态，找出最可靠的生物标志物来检测与污染有关的氧化应激。我们还通过实验处理研究了饮食中叶黄素水平是否对大山雀的抗氧化防御有任何作用，以及它们基于类胡萝卜素的羽毛颜色是否与氧化应激状态有关。我们使用抗氧化剂（GSH、类胡萝卜素）和几种抗氧化酶（GP、GR、GST、SOD 和 CAT）作为氧化应激的指标。我们没有发现饮食中金属暴露与抗氧化剂或抗氧化酶水平之间的直接联系。然而，在污染环境中，GP 的活性略高。这是由于污染区雏鸟的状况较差，因此氧化应激水平较高。我们还发现 GP 与育雏期的环境温度之间存在正相关关系，这可能是由于在温暖的天气中，部分变温动物的雏鸟代谢活动较高。GST 的活性与采样时的雏鸟数量呈正相关。在未污染的地区，育雏成功率更高，雏鸟的体重也更高。在补充类胡萝卜素的鸟类中，类胡萝卜素处理使血浆类胡萝卜素浓度增加了 2.1 倍，但与氧化应激生物标志物或金属水平无关。黄色羽毛颜色与两个研究区的饮食类胡萝卜素水平有关，但与金属暴露或氧化应激状态无关。我们的研究结果表明，在我们研究区域发现的暴露水平下，酶活性并不能表明与金属有关的氧化应激。相反，GP 可以作为与生长有关的氧化应激的指标，在污染区更为严重。然而，这种酶的活性与金属暴露没有直接关系，而更可能与育雏状况的一些与污染有关的二次变化有关。
