Immunoelectron microscopic localization of thyroglobulin (TG) in the thyroid gland in Basedow's disease

An electron microscopic immunohistochemical localization of thyroglobulin (TG) using PAP methods from Epok-812 embedded tissues has been made in human thyroids obtained from 15 patients with treated Basedow's disease aged 13 to 43 years. Follicular cells vary considerably in shape and content of cytoplasmic organelles depending mainly upon the size of follicles. Reaction product for TG coincided well with previous investigations studied by electron microscopic autoradiography and is strongly positive in most follicular lumina having no relation to their size, reabsorbed colloid droplets or small subapical vesicles. The reabsorbed colloid droplets are rarely observed in cells surrounding distended follicles and more frequently appeared in small follicles. The reabsorbed colloid droplets after fusion with lysosomes show a variable amount of reaction products from intense deposition to a complete absence of product indicating hydrolysis of TG by lysosomal enzymes. There is no reaction product in rough endoplasmic reticulum or Golgi apparatus in spite of positive reaction product in the subapical vesicles. These subapical vesicles are composed of both endocytotic and exocytotic vesicles.