Diisopropanolnitrosamine (DIPN) induced rat thyroid lesions. III. An immunohistochemical study on their functional aspects.

The functional aspects of DIPN induced rat thyroid lesions classified as in our previous studies were analyzed by immunohistochemical detection of Tg, T4, and T3 in serial or semi-serial paraffin sections. The type 1 lesions, i.e., foci of cellular alteration of individual follicles, showed the same pattern of immunostaining as seen in the surrounding hyperplastic follicles and in normal controls. On the other hand, the type 3 lesions, i.e., carcinomas, were mostly negative for T4 and T3 with only partial staining for Tg. The type 2 lesions, i.e. proliferative nodules, which might include a state of nodular hyperplasia as well as benign neoplastic nodules, demonstrated intermediate stainability between the type 1 and type 3 lesions. These results suggest that the histological structures of focal lesions of the thyroid gland may be closely related to their functional activities. Also, the importance of follicular structure formation in thyroid hormone synthesis was demonstrated in each type of focal lesion.