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PW01 Wildlife Toxicology
(PW032) Analysis of serum vitellogenin in wild-caught Morelet's crocodile, Crocodylus moreletii from Belize.
Rainwater, T1, Nespoli, LM2, McMurry, S1, Platt, S3, Selcer, K2, 1 Texas Tech University, Lubbock, TX, USA2 Duquesne University, Pittsburgh, PA, USA3 Oglala Lakota College, Kyle, SD, USA
ABSTRACT- Vitellogenin induction has been widely used as a biomarker for exposure to environmental estrogens; however, little is known about vitellogenin induction in crocodilians. In the present study, we examined serum vitellogenin from wild-caught Morelet's crocodile (Crocodylus moreletii) as part of a comprehensive study of exposure of this species to environmental contaminants in Belize. Blood was collected in the field from crocodiles of all ages and sexes during several breeding seasons. Estrogen and testosterone levels of the sera were determined by radioimmunoassay. Initially, sera from adult females with high estradiol levels were compared with sera from adult males with low estradiol levels, using denaturing gel electrophoresis (SDS-PAGE). Several high molecular weight proteins were present in female sera that were absent in male sera, indicating presumptive vitellogenin. The largest of these had a molecular weight of about 210 kDa, corresponding to the typical weight of reptilian vitellogenin. Our lab had previously developed an antibody that crossreacts with vitellogenins from a broad array of vertebrates, including the alligator (Alligator mississippiensis). Using this antibody in Western blotting, female sera showed several bands of crossreactivity not found in males. Again, the largest of these had a molecular weight of 210 kDa. An ELISA assay, using the same antibody, showed that female sera had substantially more crossreactivity than male sera, which was negligible. Screening of all crocodile samples by ELISA revealed that many adult females contained vitellogenin in their sera, as expected. However, no vitellogenin was detected in sera from males and juveniles, suggesting that these populations of crocodiles are not currently being exposed to significant levels of environmental estrogens. Assays developed for vitellogenesis in this species could be useful for studying annual reproductive cycles and for assessing exposure of wild populations to environmental estrogens.
Key words: Crocodylus moreletii, vitellogenin, biomarker, environmental estrogens
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