Expression of Bcl-2 and Bax proteins in thyroid glands of rats in experimental thyroiditis.

In the recent years, iodine was associated to the development of apoptosis in thyroid diseases. The aim of the present study is to determine the expression of pro-apoptotic and anti-apoptotic proteins, Bax and Bcl-2, in a Wistar rat experimental model of thyroiditis induced by administration of different doses of potassium iodide. Immunohistochemical staining was done with chromogen diaminobenzidine on avidin-biotin peroxidase using the Animal Research Kit (ARK), stained with antibodies to Bcl-2 and Bax proteins. The intensity and distribution of positive staining were evaluated by light microscopy on a scale of 0 to 4. Bax protein was expressed in the area of regenerating follicular cells in high percent in potassium iodide treated rats, but was not expressed in thyrocytes from control rats. Bcl-2 expression was constantly observed in thyrocytes of the control group and in the mantle-zone of lymphoid follicular infiltrates. Our results show that Bax expression is significantly higher in the Wistar rat experimental model of thyroiditis than in the control group. These data suggest that the increased expression of Bax may contribute to the role of apoptosis in the pathogenesis of experimental thyroiditis.