In Ovum Exposure to Atrazine Causes Thyroid Disruption in Juvenile South American Crocodilian, Caiman latirostris

TRUTER, J.C.; MUÑOZ-DE-TORO, M.; GALOPPO, G.H.; LUQUE, E.H.; TAVALIERI, Y.E.; VAN WYK, J.H.

Ciudad del Cabo

Congreso; SETAC Africa 9th Biennial Conference; 2019

SETAC - SRA

Atrazine (ATZ) is an herbicide with estrogenic and anti-androgenic activities. ATZ binds thyroid hormone receptor and environmentally relevant concentrations disrupt developmental processes regulated by thyroid hormones suggesting that ATZ could disrupt thyroid histo-functionality. Caiman latirostris is a crocodilian species highly sensitive to endocrine disruption that inhabits wetlands nearby agricultural lands in Argentina. The aims of this study were to describe thyroid histo-architecture, to characterize thyroid histo-functional biomarkers and to assess long term effects of prenatal exposure to ATZ in juvenile male and female caimans. Eggs (n=45) collected from wetlands in a Natural Reserve with low anthropogenic intervention were incubated at male or female producing temperature and exposed to 0.2 ppm ATZ (environmentally relevant dose) or vehicle prior to temperature sex determination window. Hatchlings were raised under controlled conditions until juvenile. At sacrifice, thyroid glands were dissected, fixed and processed until paraffin embedded. Using histological sections stained with PAS, histo-functional parameters such as percentage of the thyroid occupied by stroma or follicles; follicular epithelial height, follicular perimeter and % of the intrafollicular area occupied by colloid were assessed. Estrogen receptor-alpha (ERα), Androgen receptor (AR) and Proliferation Cell Nuclear Antigen expressions were revealed by immunohistochemistry and expressed as percentage of positive epithelial cells. Male and female thyroids exhibit no differences in the evaluated parameters. Thyroid glands from ATZ-exposed caimans showed increased percentage of the gland occupied by stroma and decreased percentage of intrafollicular area occupied by colloid. ATZ-exposed females showed increased follicular epithelial height (16.44 vs 10.84, p=0.0206) and decreased epithelial AR expression (50.06 vs 67.68, p