Relationship of Blood Mercury Levels to Health Parameters in the Loggerhead Sea Turtle (Caretta caretta)

Background: Mercury is a pervasive environmental pollutant whose toxic effects have not been studied in sea turtles in spite of their threatened status and evidence of immunosuppression in diseased populations. Objectives: In the present study we investigate mercury toxicity in loggerhead sea turtle...

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Bibliographic Details
Published in:Environmental health perspectives 2007-10, Vol.115 (10), p.1421-1428
Main Authors: Day, Rusty D, Segars, Al L, Arendt, Michael D, Lee, A Michelle, Peden-Adams, Margie M
Format: Article
Language:English
Subjects:
Analysis and chemistry
Animal Diseases - chemically induced
Animals
Aspartate Aminotransferases - blood
Aspartate Aminotransferases - drug effects
Atlantic Ocean
B lymphocytes
Blood
Blood plasma
Caretta caretta
Cell Proliferation - drug effects
Cells, Cultured
Correlations
Creatine Kinase - blood
Creatine Kinase - drug effects
Distribution
Environmental Exposure - adverse effects
Environmental Exposure - analysis
Environmental Monitoring
Health aspects
Hematocrit
Hematocrit - veterinary
Immune System - drug effects
Loggerhead turtle
Lymphocyte Count
Lymphocyte proliferation
Lymphocytes
Mercury
Mercury - blood
Mercury - toxicity
Methylmercury Compounds - blood
Methylmercury Compounds - toxicity
Sea turtles
Southeastern United States
T lymphocytes
Turtles
Turtles - blood
Turtles - physiology
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Summary:Background: Mercury is a pervasive environmental pollutant whose toxic effects have not been studied in sea turtles in spite of their threatened status and evidence of immunosuppression in diseased populations. Objectives: In the present study we investigate mercury toxicity in loggerhead sea turtles (Caretta caretta) by examining trends between blood mercury concentrations and various health parameters. Methods: Blood was collected from free-ranging turtles, and correlations between blood mercury concentrations and plasma chemistries, complete blood counts, lysozyme, and lymphocyte proliferation were examined. Lymphocytes were also harvested from free-ranging turtles and exposed in vitro to methylmercury to assess proliferative responses. Results: Blood mercury concentrations were positively correlated with hematocrit and creatine phosphokinase activity, and negatively correlated with lymphocyte cell counts and aspartate aminotransferase. Ex vivo negative correlations between blood mercury concentrations and B-cell proliferation were observed in 2001 and 2003 under optimal assay conditions. In vitro exposure of peripheral blood leukocytes to methylmercury resulted in suppression of proliferative responses for B cells (0.1 µg/g and 0.35 µg/g) and T cells (0.7 µg/g). Conclusions: The positive correlation between blood mercury concentration and hematocrit reflects the higher affinity of mercury species for erythrocytes than plasma, and demonstrates the importance of measuring hematocrit when analyzing whole blood for mercury. In vitro immunosuppression occurred at methylmercury concentrations that correspond to approximately 5% of the individuals captured in the wild. This observation and the negative correlation found ex vivo between mercury and lymphocyte numbers and mercury and B-cell proliferative responses suggests that subtle negative impacts of mercury on sea turtle immune function are possible at concentrations observed in the wild.
ISSN:0091-6765
1552-9924
DOI:10.1289/ehp.9918