Immunocytochemistry of thyroid C-cell complexes in dogs.

Ten thyroid C-cell complexes from five male and five female Beagle dogs, 1 to 2 years old, were studied using single and double immunocytochemical staining with the peroxidase-antiperoxidase technique. The antigens tested included thyroglobulin, calcitonin, calcitonin gene-related peptide, somatostatin, neuron specific enolase, and neurotensin. All C-cell complexes contained four cell types in various proportions: 1) follicular cells staining for thyroglobulin; 2) C-cells staining for calcitonin, calcitonin gene-related peptide, and neuron specific enolase; 3) stellate cells and cuboidal cells in follicle-like structures staining positively for somatostatin; and 4) undifferentiated cells staining negatively for all antigens. No positive immunoreactivity for neurotensin was detected. These findings support the hypothesis that thyroid C-cell complexes are ultimobranchial remnants that can give rise to thyroid follicles and C-cells.