Immunohistochemical Studies on the Development of Endocrine Cells in the Thyroid and Parathyroid Glands in the Golden Hamster

Abstract

The development of endocrine cells in the thyroid and parathyroid glands in the golden hamster was studied immunohistochemically in relation to the formation of these glands. The thyroid was formed on day 9 of gestation by the ventral outpocketing of the foregut between the first and second branchial pouches. The thyroid epithelial cells were faintly thyroglobulin-immunoreactive on day 10.5 of gestation. This immunoreaction became intense thereafter, but was almost confined to the cytoplasm of epithelial cells until birth. It appeared in the follicular lumen in newborn animals. The ultimobranchial body was derived from the fifth pouch and fused with the thyroid on day 12 of gestation. Calcitonin-immunoreactive cells first appeared on day 14 of gestation in the dorsomedial part of the thyroid derived from the ultimobranchial body and increased in number and intensity thereafter. Somatostatin-immunoreactive cells also appeared in the dorsomedial part of the thyroid derived from the ultimobranchial body on day 13 of gestation, and increased in number in newborn animals, but decreased thereafter. The parathyroid was derived from the third pouch, situated on day 13 of gestation on the dorsolateral side of the thyroid, and surrounded by a common capsule with the thyroid. Parathormone-immunoreactive cells first appeared on day 15 of gestation in the parathyroid and increased in number and intensity after birth.