In ovo Exposure to Endosulfan Modified Thyroid Histofunctional Biomarkers in Prepubertal Juvenile Caiman latirostris Females.

MONICA MUÑOZ-DE-TORO; YAMIL E. TAVALIERI,; ENRIQUE H. LUQUE.; GONZALO SCHIERANO-MAROTTI; MARIO OSTI; GERMÁN H. GALOPPO

Otro; 25th Working Meeting of the Crocodile Specialist Group; 2018

Thyroid hormones play an important role on development, growth and reproduction invertebrate species. It is suggested that endocrine disruptors wildlife exposure,particularly during prenatal life, could affect thyroid function having consequences laterin life. Caiman latirostris is highly sensitive to endocrine disruption but little is knownabout Caiman latirostris thyroid histofunctionality and hormonodependence and itssensibility to endocrine-disrupting chemicals. Endosulfan is an environmentallyubiquitous pesticide classified as xenoestrogen. Previously we have demonstrated thatEndosulfan in ovo treatment modified T3/body weight ratio and induced a decreasingtrend on T3 plasma levels in Caiman latirostris. In rats, neonatal exposure toEndosulfan increases ERα level in uterus and mammary gland. Moreover, Endosulfanhas been detected in Caiman latirostris eggs demonstrating natural prenatal exposure.The aim of this study was to characterize thyroid histofunctional biomarkers in juvenilemales and females Caiman latirostris and to assess the effect of prenatal exposure toEndosulfan on thyroid histoarchitecture and histofunctionality. Eggs from lowanthropogenic intervention areas were exposed to Endosulfan or vehicle (ethanol) priorto temperature sex determination. Vehicle treated eggs were equally distributed andincubated at male or female producing temperature. Eggs exposed to 20ppm ofEndosulfan were incubated at female-producing temperature. Hatchlings were raisedunder controlled conditions until juvenile stage. Upon sacrifice, thyroid glands weredissected, formaldehyde-fixed and processed until paraffin embedded. Histofunctionalparameters (percentage of the gland occupied by stroma, epithelium, or follicularcolloid; follicle density and follicular size) were assessed using histological sectionsstained with PAS. Follicular size was categorized into three groups, small, medium andlarge follicles. Estrogen receptor-alpha (ERα) expression was revealed byimmunohistochemistry and expressed as percentage of positive cell. Nonehistofunctional parameter but percentage of large follicles showed sexual dimorphism.Thyroid gland follicular epithelia express ERα suggesting that it could be a target ofendocrine-disrupting chemicals possibly acting through steroid hormone pathway.Thyroid glands from Endosulfan treated female animals showed a decreased follicularcolloid area and increased ERα epithelial expression. Based on previous results on T3,these findings suggest that Endosulfan interferes with thyroid hormones plasmaconcentration, and colloid depletion could be the response mechanism for maintainingcirculating thyroid hormones level. As far as we know, this is the first time that Caimanlatirostris thyroid gland histofunctionality is described. Additionally, this study alertsabout the effects of Endosulfan environmental pollution on Caiman latirostris thyroidhomeostasis.