RESUMO
<p><b>OBJECTIVE</b>To investigate the effects of ammonium perchlorate (AP) on thyroid functions and mRNA expression levels of thyroglobulin (Tg) and thyroperoxidase (TPO) genes of rats.</p><p><b>METHODS</b>Thirty SD male rats were randomly divided into six groups: control group, iodine-deficient group, low dose AP group (130 mg/kg), moderate dose AP group (260 mg/kg), high dose AP group (520 mg/kg) and high iodine-combined group. After the rats were exposed orally for 90 days, serum free-thyroxine (FT(4)), free-triiodothyronine (FT(3)) and thyroid stimulating hormone (TSH) were measured using radioimmunoassays. mRNA expression levels of thyroglobulin (Tg) and thyroperoxidase (TPO) genes were detected by real-time quantitative PCR.</p><p><b>RESULTS</b>Serum FT(4) levels in moderate dose AP group and high dose AP group were [(9.540 ± 1.327) fmol/ml] and [(6.509 ± 1.949) fmol/ml] respectively, which were significantly lower than that [(13.505 ± 1.276) fmol /ml] in control group (P < 0.05 or P < 0.01). Serum TSH level in high dose AP group was [(1.227 ± 0.295) mIU/L], which was significantly higher than that [(0.545 ± 0.282) mIU/L] in control group (P < 0.05). The mRNA expression levels of thyroglobulin (Tg) gene in all groups exposed to AP were significantly lower than that in control group (P < 0.01). The mRNA expression level of thyroperoxidase (TPO) gene in high dose AP group was significantly higher than that in control group (P < 0.05).</p><p><b>CONCLUSION</b>AP can reduce the serum FT(3) and FT(4) levels of rats, increase the serum TSH level of rats and decrease obviously the mRNA expression levels of Tg and TPO genes. In addition, high iodine can reduce the toxic effects of AP on thyroid gland of rats to some extent.</p>