Post‐hatching developmental changes in the adrenal gland of the Japanese quail (Coturnix coturnix japonica): Histological, immunohistochemical, and electron microscopic studies

The adrenal glands are paired abdominal endocrine organs vital to the bird's health. The present research aimed to provide a comprehensive examination of the histological, ultrastructural, and immunohistochemical investigations of the adrenal gland in Japanese quail during the post hatching period. The current study was performed on 21 healthy Japanese quail chicks at different post hatching periods. Our results showed the adrenal gland is surrounded by a connective tissue capsule, which consists of dense collagen fibers containing large blood vessels, chromaffin cells, autonomic ganglia, fibroblasts, and migrating Schwann cells. The zonation of the adrenal gland is composed of a subcapsular layer, a peripheral zone, and a central zone, which gets more pronounced with age. At the ultrastructural level, the interrenal cells take the steroid-secreting cells characters; they have varying amounts of lipid droplets and abundant mitochondria. Adrenal medullary chromaffin cells showed positive immunoreactivity to the NSE. With increasing age, the chromaffin tissue's Sox10 immunoreactivity increased. β-catenin is expressed within the plasmalemma and the cytoplasm of the interrenal and chromaffin cells and its reactivity increased with age, especially in the chromaffin cells. Our results indicate the adrenal gland undergoes significant morphological changes during the postnatal life. Overall, the postnatal period is an important time for the development and maturation of the adrenal glands.