Influence of chronic perfluoroalkyl ether sulfonate exposure via drinking water on thyroid function of Sprague-Dawley rats

Objective  To investigate the influence of chronic exposure to perfluoroalkyl ether sulfonate (F-53B) via drinking water on the thyroid function of Sprague-Dawley (SD) rats.

Methods  A total of 40 specific pathogen-free male SD rats were randomly divided into solvent control group (dimethyl sulfoxide, DMSO) and exposure groups (1, 10, 100, and 1 000 μg/L F-53B), with 8 rats in each group. The final concentration of DMSO was 0.004% (volume fraction) for each group, and the rats were exposed to F-53B through drinking water for 6 months since June 2020. The serum levels of total cholesterol (TCHO), high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C) were measured, as well as the serum levels of tetraiodothyroxine (T4), triiodothyronine (T3), thyroid stimulating hormone (TSH), thyrotropin-releasing hormone (TRH), and thyroid peroxidase antibody (TPO-Ab). Histopathological changes of the thyroid were also observed.

Results  After 6 months of F-53B exposure, there were no significant differences among the exposure groups in body weight, thyroid weight, and organ coefficient of rats in each exposure group (F=0.61-2.20, P>0.05). Compared with the control group, there were no significant differences in the serum levels of TCHO, HDL-C, and LDL-C among the exposure groups (F=0.26-0.84, P>0.05). There were significant differences in thyroid-related hormones between the exposure groups (F=30.4-131.3, P < 0.05), among which T3 and T4 decreased with the increase in the exposure dose of F-53B, while the levels of TSH, TRH and TPO-Ab increased in a dose-dependent manner, with significant differences among the 10, 100, and 1 000 μg/L exposure groups (adjusted P < 0.05). Pathological result showed mild thyroid follicular hyperplasia in thyroid tissue in the highest dose group.

Conclusion  Chronic F-53B exposure can induce structural alterations and functional abnormalities in the thyroid tissue of rats, which may be associated with the disturbance of iodothyronine coupling during thyroid hormone synthesis.