The localization of the low-molecular-weight heavy-metal-binding protein metallothionein (MT) in the thyroid gland and medullary thyroid carcinoma was investigated by an immunohistochemical technique, and the amount of MT in the thyroid gland was assayed by radioimmunoassay.
MT was immunohistochemically identified in epithelial cells of follicular and parafollicular cells. Both the cytoplasm and the nuclei of the cells stained positive for MT. The nuclear staining for MT was strong. The follicular epithelial cells and colloid were positive for thyroglobulin, and the parafollicular cells were strongly positive for calcitonin.
Medullary thyroid carcinoma was strongly positive for calcitonin, but most tumor cells were negative for MT. MT-positive cells in the tumor were sporadic, and both their nucleus and cytoplasm stained positive.
Radioimmunoassay revealed high levels of MT in the thyroid gland, about 148.7±45.0 μg/g wet weight.