Delta-aminolevulinic acid dehydratase (delta ALAD) activity in four free-living bird species exposed to different levels of lead under natural conditions

作者：Espin Silvia; Martinez Lopez Emma; Jimenez Pedro; Maria Mojica Pedro; Garcia Fernandez Antonio J^*

来源：Environmental Research, 2015, 137: 185-198.

DOI：10.1016/j.envres.2014.12.017

• delta ALAD
• Pb
• Blood
• Birds

The purposes of this study were: (1) to determine the delta ALAD activity and delta ALAD ratio in blood of four free-living bird species (Griffon vulture, Eagle owl, Slender-billed gull and Audouin's gull); (2) and to investigate the correlations between delta ALAD activity/ratio and Pb concentrations in blood samples. A decrease was observed in delta ALAD activity in Griffon vultures and Eagle owls exposed to Pb. In addition, negative relationships were found between delta ALAD ratio or delta ALAD activity and Log blood Pb levels in Griffon vultures and Eagle owls, and these relationships were stronger in areas with the highest Pb exposure. We provide equations that may be helpful to estimate delta ALAD activity and delta ALAD ratio using blood Pb concentrations. Regarding gull species, delta ALAD activity found in the present study may be considered the normal activity in Slender-billed gull and Audouin's gull species, since very low blood Pb concentrations and no correlations were found in these species. Although both delta ALAD activity and delta ALAD ratio are sensitive biomarkers of Pb exposure and effect in birds, the use of delta ALAD ratio may improve the results. Besides, this study provides blood threshold concentrations at which Pb bears effects on delta ALAD enzyme (5 mu g/dl in Eagle owl; 8 mu g/dl in Griffon vulture; and probably >2 mu g/dl in Slender-billed gull and Audouin's gull). Our findings show that Eagle owl seems to be more sensitive to delta ALAD enzymatic inhibition by Pb than Griffon vultures. Eagle owls and Griffon vultures exhibited up to 79% and 94% decrease in delta ALAD activity when blood Pb concentrations exceeded 19 and 30 mu g/dl, respectively. Regarding the effects related with delta ALAD inhibition, significant negative correlations were found between delta ALAD activity and hematocrit in Eagle owls and Griffon vultures, which may be related to compensatory response associated with a decrease in delta ALAD activity. In addition, an effect on creatine kinase activity and total proteins in plasma was found in Griffon vultures. The significant negative correlations found between delta ALAD activity and tGSH in Griffon vulture, and between delta ALAD activity and Log CAT activity in Eagle owls, may be related to a protective response of antioxidant system against reactive oxygen species (ROS). The negative relationship found between delta ALAD activity and TBARS levels in Griffon vulture is probably related to an induction of lipid peroxidation by ROS that may be generated by delta ALA accumulation when delta ALAD activity is depressed. delta ALAD activity and delta ALAD ratio in blood are suggested as important nondestructive biomarkers for Pb exposure and effect for future biomonitoring studies in Griffon vulture and Eagle owl. Further studies are recommended to provide new data on Pb concentrations at which delta ALAD activity is affected in different wild bird species and to elucidate why different species tolerate Pb in different ways.

• 出版日期2015-2