RESUMO
BACKGROUND: Estrogen promotes the growth of thyroid cells. Therefore, we analyzed the influence of estrogen and selective estrogen receptor modulators (SERMs) on the expression of vascular endothelial growth factor (VEGF) and nitric oxide synthase III (NOS III) in the thyroid gland of ovariectomized (Ovx) rats. METHODS: Wistar rats were divided into five groups, and bilateral ovariectomies were performed, except on the Sham-operated controls (Sham). Rats were grouped as follows: Sham; Ovx; and Ovx rats treated with daily subcutaneous injections of estradiol benzoate 3.5 microg/kg, tamoxifen 2.5 mg/kg, or raloxifene 2.5 mg/kg for 50 consecutive days. Control animals received vehicle (propyleneglycol), and at the end of the treatment, rats were sacrificed. The thyroid glands were excised, weighed, and processed for analysis of the expression of VEGF or NOS III by immunohistochemistry. The mean vascular areas were evaluated by immunodetection of alpha-smooth muscle actin. RESULTS: Thyroid weight and mean vascular area were lower in Ovx as compared with Sham, Ovx + estradiol benzoate, Ovx + Tam, or Ovx + Ral (p < 0.01). VEGF (p < 0.01) and NOS III expressions (p < 0.05) were significantly lower in the Ovx group, as compared with Sham, Ovx + estradiol benzoate, Ovx + Tam, and Ovx + Ral. Immunoreactivity for both VEGF and NOS III was mainly detected in the cytoplasm of the follicular epithelial cells. CONCLUSIONS: Our data suggest that estrogen and SERMs regulate the thyroid gland vascularization and that tamoxifen and raloxifene behave like estrogen does. Estrogen and SERMs upregulate VEGF and NOS III in such a way as to reverse the effects detected on the thyroid microvasculature of the Ovx rats.
Assuntos
Estradiol/análogos & derivados , Estrogênios/farmacologia , Óxido Nítrico Sintase Tipo III/metabolismo , Moduladores Seletivos de Receptor Estrogênico/farmacologia , Glândula Tireoide/metabolismo , Regulação para Cima/efeitos dos fármacos , Fatores de Crescimento do Endotélio Vascular/metabolismo , Actinas/metabolismo , Animais , Estradiol/farmacologia , Feminino , Imuno-Histoquímica , Microvasos/efeitos dos fármacos , Tamanho do Órgão , Ovariectomia , Cloridrato de Raloxifeno/farmacologia , Distribuição Aleatória , Ratos , Ratos Wistar , Tamoxifeno/farmacologia , Glândula Tireoide/irrigação sanguínea , Glândula Tireoide/citologia , Glândula Tireoide/efeitos dos fármacos , Útero/anatomia & histologia , Útero/efeitos dos fármacosRESUMO
We aimed to analyze the effects of raloxifene and estrogen on thyroid gland morphology of ovariectomized rats. Raloxifene treatment led to effects similar to those of estrogen on thyroid glands from ovariectomized rats, so that both were able to normalize the changes detected after ovariectomy.