Erythrocyte ALA-d activity in experimentally lead-poisoned ducks and its change during treatment with disodium calcium EDTA

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

The purposes of this study were: (1) to determine the δALAD activity and δALAD 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 δALAD activity/ratio and Pb concentrations in blood samples. A decrease was observed in δALAD activity in Griffon vultures and Eagle owls exposed to Pb. In addition, negative relationships were found between δALAD ratio or δALAD 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 δALAD activity and δALAD ratio using blood Pb concentrations. Regarding gull species, δALAD 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 δALAD activity and δALAD ratio are sensitive biomarkers of Pb exposure and effect in birds, the use of δALAD ratio may improve the results. Besides, this study provides blood threshold concentrations at which Pb bears effects on δALAD enzyme (5µg/dl in Eagle owl; 8µg/dl in Griffon vulture; and probably >2µg/dl in Slender-billed gull and Audouin's gull). Our findings show that Eagle owl seems to be more sensitive to δALAD enzymatic inhibition by Pb than Griffon vultures. Eagle owls and Griffon vultures exhibited up to 79% and 94% decrease in δALAD activity when blood Pb concentrations exceeded 19 and 30µg/dl, respectively. Regarding the effects related with δALAD inhibition, significant negative correlations were found between δALAD activity and hematocrit in Eagle owls and Griffon vultures, which may be related to compensatory response associated with a decrease in δALAD 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 δALAD activity and tGSH in Griffon vulture, and between δALAD 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 δALAD activity and TBARS levels in Griffon vulture is probably related to an induction of lipid peroxidation by ROS that may be generated by δALA accumulation when δALAD activity is depressed. δALAD activity and δALAD 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 δALAD activity is affected in different wild bird species and to elucidate why different species tolerate Pb in different ways.

Lead contamination in American woodcock (Scolopax minor) from Wisconsin

An initial survey of lead levels in American woodcock (Scolopax minor) from Wisconsin was conducted in 1998 using wing bones from hunter-donated woodcock. The results of this initial survey indicated that young-of-year woodcock were accumulating extremely high levels of lead in their bones. Similar collections were made (using steel shot) between 1999 and 2001. The combined results of this collection indicated that 43.4% of young-of-year woodcock (range 1.5-220.0 microg/g dry wt) and 70% of woodcock chicks (range 9.6-93.0 microg/g dry wt) had bone lead levels in the elevated range (>20 microg/g dry wt). Blood samples were collected from chicks at a site considered elevated based on bone lead results (Mead Wildlife Area) and a site considered background (Navarino Wildlife Area). These samples were analyzed for lead concentration and aminolevulinic acid dehydratase activity. The mean blood lead concentrations of woodcock chicks from both sites did not reach levels that are considered elevated in waterfowl (>0.200 microg/ml). However, blood lead concentrations of chicks from the Mead Wildlife Area were significantly higher than lead levels in chicks from Navarino Wildlife Area (p = 0.002). Although the ultimate sources of lead exposure for Wisconsin woodcock currently remain unidentified, anthropogenic sources cannot be ruled out. Our results indicate that elevated lead exposure in Wisconsin woodcock is common and begins shortly after hatch.