Electron microscopic observations on the localization of peroxidase in the follicular cells of the human thyroid gland

Abstract

It has been demonstrated recently in many laboratories that thyroid peroxidase plays a direct role in the oxidation of iodine, iodination of thyroglobuline, and formation of triiodothyronine and thyroxine.
On the other hand, many investigators have reported the localization of thyroperoxidase activity in cytochemical studies using 3.3'-diaminobenzidine (DAB), but somewhat different results were obtained by these investigators.
Peroxidase activity in thyroid follicular cells reported until now is localized in the following sites : the perinuclear cisternae, cisternae of the rough-surfaced endoplasmic reticulum, the inner few lamellae of the Golgi apparatus, some apical vesicles and the external surface of microvilli.
But the thyroid material of these studies was almost all from experimental animals.
We have now electron-microscopically investigated the localization of peroxidase in human thyroid glands, by staining histochemically (DAB), thyroid slices previously fixed with glutaraldehyde.
We found that the peroxidase activity was localized mainly in the colloid droplet which has never been reported by other investigators.