Oxidative stress biomarkers in Eurasian eagle owls (Bubo bubo) in three different scenarios of heavy metal exposure

Abstract

The main aim of the present study is the assessment of oxidative stress related to metals in the Eurasian eagle owl (Bubo bubo) from three areas (agricultural and rural area, industrial area, and mining area) of Murcia, Southern Spain. Mean blood metal concentrations were Cd=0.07±0.21, Pb=3.27±5.21, Cu=10.62±4.77, Zn=311.47±67.14, Hg=2.32±3.83 μg/dl wet weight. Although individuals from the mining area had significant higher Pb and Hg concentrations, and significant lower glutathione-S-transferase (GST) and catalase (CAT) activities in red blood cells (RBC); the lack of differences in oxidative damage to membrane lipids (TBARS) among areas suggests that the antioxidant capacity of the different populations is able to deal with oxidant species and maintain TBARS levels in the same amount. Despite the low levels of metals, several oxidative stress biomarkers were correlated with metal concentrations. This study provides threshold concentrations at which metals cause effects on the antioxidant system in Eagle owls. Blood Cd concentrations greater than 0.3 μg/dl produced an inhibition in GPx (32%) and CAT (26%) activity in RBC. However, Cd concentrations higher than 0.02 μg/dl were enough to produce an inhibition of these enzymes. Regarding Pb levels, blood concentrations above 2 μg/dl produced an inhibition of 8% and 10.5% in GPx and CAT activities, respectively, in RBC. A depletion of 16% and 4% in tGSH levels was associated with Pb concentrations higher than 15 and 3 μg/dl, respectively, in individuals from the ancient mine site. In addition, Pb concentrations above 2 and 10 μg/dl produced a TBARS induction of 10% and 28%, respectively, in individuals from both the industrial and the mining area. Finally, Hg concentrations greater than 3 and 10 μg/dl resulted in a TBARS induction of 102% and 190%, respectively, in Eurasian eagle owls from the industrial area. Our findings show that Pb may produce effects on oxidative stress biomarkers in Strigiformes at lower concentrations than those typically accepted for considering physiological effects in Falconiformes (20 µg/dl in blood). In addition, we provide new data on Hg and Cd concentrations related to effects in the antioxidant system.

Keywords: Biomarkers; Bubo bubo; Eurasian eagle owl; Heavy metals; Oxidative stress.