METALLOTHIONEIN IN THE THYROID-GLAND

The localization of the low-molecular-weight heavy-metal-binding prote in metallothionein (MT) in the thyroid gland and medullary thyroid car cinoma was investigated by an immunohistochemical technique, and the a mount of MT in the thyroid gland was assayed by radioimmunoassay. MT w as immunohistochemically identified in epithelial cells of follicular and parafollicular cells. Both the cytoplasm and the nuclei of the cel ls stained positive for MT. The nuclear staining for MT was strong. Th e follicular epithelial cells and 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 spora dic, and both their nucleus and cytoplasm stained positive. Radioimmun oassay revealed high levels of MT in the thyroid gland, about 148.7 +/ - 45.0 mu g/g wet weight.