Endogeneous peroxidase activity in the frog thyroid gland

Summary The fine structural localization of the endogeneous peroxidase activity in the thyroid of the young frog was studied. The reaction product for peroxidase was observed over the peripheral luminal colloid and apical region of the follicular epithelial cell. Most apical small granules and some parts of Golgi lamellae and a few Golgi vesicles were specifically stained. The cisternae of rough endoplasmic reticulum and the nuclear cisternae did not demonstrate any positive reaction for peroxidase activity with difference from that of various cells of mammalia. In this study, only mature peroxidase seems to be positive for its reaction and the enzyme in the rough endoplasmic reticulum is considered to be too immature to react for DAB method in the frog thyroid cell. The relationship between the localization of peroxidase reaction and the site of the iodination of thyroglobulin was discussed.