[Time-dependent effects of pentabrominatefl diphenyl ethers on thyroid hormones and histological structure of...

To study the time-dependent effects of pentabrominated diphenyl ethers on thyroid hormones and the histological structure of thyroids in rats.

One hundred healthy 4-week-old SD rats were randomly divided into 10 groups. The rats in the experimental groups were orally administered with pentabrominated diphenyl ethers (BDE-99) at a dose of 60 mg/kg for 10, 15, 20, 30 and 40 days respectively, while the rats in the control groups received equal volumes of corn oil for the same periods of time. Serum FT4, FT3 and TSH were measured by radioimmunoassay. Sections of thyroids were dyed with hematoxylin-eosin (HE) to detect pathological alterations in thyroid tissues.

Decreased serum FT4 and FT3 and increased TSR were detected in the BDE-99 treated rats at DiS and D20. No significant differences of serum hormones were found between the experimental and control groups at D10, D30 and D40. The thyroid follicle epithelium of the BDE-99 treated rats proliferated into multiple-layer structure at DiS. At D20, proliferative plaque formed in local areas. Solid buds and follicles secondary to the solid buds were detected at D30 and D40.

BDE-99 leads to structural changes of thyroids, reduces serum FT4 and FT3 and increases TSR. The time-dependent effects are evident in a damage and compensate pattern.