Introduction: A complex cocktail of poorly biodegradable chemicals is ubiquitous in the modern environment and exposure to such chemicals contributes to diseases including thyroid dysfunction. The thyroid gland regulates growth and function of multiple organs and we previously showed that exposure to xenotoxicants (via maternal grazing on sewage sludge fertilised pastures) disturbed fetal sheep thyroid development. Our aim here was to assess whether the effects seen in fetal sheep persist into adulthood.
Materials and methods: Thyroids from sheep that grazed on control or sewage sludge-fertilised pastures throughout their lives (gestation and lactation via the mother and post-weaning grazing) were divided in four groups (n=610/group) according sex and treatment. Thyroid morphology was assessed using H&E staining. Transcript levels and expression of proteins important for thyroid function were measured using real-time PCR, western blot, and immunohistochemistry respectively in control and treated animal thyroids and livers.
Results and discussion: No gross histological differences between control and treated groups were observed. Most thyroids examined contained benign non-neoplastic cysts that were significantly larger in males (P<0.005, irrespective of treatment). No difference in thyroid-specific TTF1, PAX8, TG, DIO2, CD31, ESR1, TSHR, SLC5A5, TPO, and THRA or liver-specific THRB and SERPINA7 transcript levels were found among groups indicating normal thyroid function overall. Consistent with these findings, plasma free T3 and free T4 were not altered by sewage sludge exposure. The results here show that even though exposure to complex cocktails of everyday chemicals affects the ovine thyroid during prenatal development, no obvious abnormalities are seen in adulthood.
02 - 04 Sep 2014
World Congress of Reproductive Biology