Kinetics, dose--response, and excretion of methylmercury in free-living adult Cory's shearwaters.
We evaluated methylmercury (MHg) kinetics, dose--responses, and excretion in free-living adult Cory's shearwaters using a nondestructive multi-tissue approach. Elimination of MHg in blood comprised an initial fast phase, with half-time of 1 d, and a slow terminal phase with half-time between 44 and 65 d. Molt was a crucial factor in determining the rate of MHg elimination. Half-times were independent of dose. A relationship between steady-state blood concentrations and dietary intake of MHg was derived. Ratios between Hg concentrations in eggs or hatchlings' plumage and parental blood were independent of dose, with tissue--blood partition coefficients identical to those in controls. Dose--response relationships were linear. Females were subjected to Hg concentrations 18% higher than males but exhibited a 10% lower dose--response in blood. The difference is not fully accounted for by excretion into the egg and may be due to unidentified sex-related differences in physiology. Excretion rates into plumage showed no dose dependency but were higher (33% of intake) in birds exposed during molt than in birds dosed 2 months before the start of molt. Hg excretion through the skin in exfoliated epidermal cells that adsorb into plumage was estimated to represent 8% of the intake. The results of this study may be used in advanced modeling of the kinetics of MHg in adult birds to fill the current gap of a bioenergetic model for avian exposure to MHg.
Monteiro
L R
LR
Department of Oceanography & Fisheries, University of the Azores, 9900 Horta, Portugal.
Furness
R W
RW
D000818:Animals; D001717:Birds / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D004531:Eggs; D004785:Environmental Pollutants / Q000097:blood* / Q000378:metabolism; D006207:Half-Life; D007700:Kinetics; D008660:Metabolism; D008767:Methylmercury Compounds / Q000097:blood* / Q000378:metabolism
D004785:Environmental Pollutants; D008767:Methylmercury Compounds