DISTRIBUTION OF C-CELLS IN PARATHYROID GLAND IV AND THYMUS IV OF DIFFERENT MAMMALS STUDIED BY IMMUNOPEROXIDASE METHOD USING ANTI-CALCITONIN AND ANTI-C-THYROGLOBULIN ANTISERA
In order to determine whether or not the C-cells are distributed in parathyroid glands and thymuses as well as in thyroid glands, the thyroid glands with surrounding tissues of ten rabbits, sixteen cats, three goats and ninety-two dogs were cut into the complete serial sections, and examined by immunoperoxidase method using the specific antisera to human calcitonin, porcine calcitonin and canine C-thyroglobulin. The C-cells of each animal species were filled with numerous immunoreactive secretory granules after the specific immunoperoxidase staining and distinguished easily from nonreactive thyroid follicular cells, parathyroid cells and thymic cells. In rabbits, cats and goats the C-cells were almost constantly observed in the parathyroid glands IV. A large number of C-cells were widely dispersed among the parathyroid cells as single cells or as small clusters of cells. Of 92 dogs examined, nine revealed the presence of C-cells in parathyroid IV. Their distribution was mainly restricted to the peripheral regions of parathyroid parenchyma. Thymus IV was frequently observed adjacent to parathyroid IV in thyroid lobes of cats and dogs. Ten out of 12 thymuses IV in cats and fourteen out of 15 thymuses IV in dogs revealed the distribution of C-cells. No C-cells were found in the parathyroid gland III and thymus III. In conclusion, the C-cells of some mammals are distributed not only in the thyroid gland but also in the parathyroid gland IV and thymus IV intimately associated with the ultimobranchial bodies during the fetal period. That is, the origin of calcitonin is not restricted to the thyroid gland, though it is usually the most significant source.