Functional Differentiation of the Pituitary Gland during Development of the Domestic Ring Dove (Streptopelia roseogrisea)

Abstract

The development and differentiation of the anterior pituitary gland was studied in the domestic ring dove (Streptopelia roseogrisea) and compared with the pattern of body growth. By combining histochemical staining techniques with immunohistochemical methods, cells producing prolactin (PRL), growth hormone (GH), thyrotropic hormone (TSH), and adrenocorticotropic hormone were identified in the pituitary of the developing ring dove. The distribution of the four cell types within the anterior pituitary was illustrated by three-dimensional reconstruction from immunohistochemically stained serial sections. The pattern, which was shown to change through embryonic and juvenile development, was described and compared with examples from other vertebrate classes.The analysis of body growth showed that the development of the nestlings could he divided into two distinct growth phases. The first seven days were characterized by a consistently high rate of body growth, whereas after Day seven the growth rate was markedly reduced. Although GH-immunoreactive cells formed the dominant cell type in the pituitary during the whole postembryonic development, there was no correlation between the rate of body growth and the abundance of GH-immunoreactive celIs in the pituitary. In contrast, changes in the abundance of PRL- and TSH-immunoreactive cells were observed simultaneously with the transition from the first to the second growth phase. The proportion of PRL-immunoreactive cells was relatively high during the first seven days, whereas TSH-immunoreactive cells became more abundant during the second growth phase. It is therefore postulated that PRL and TSH play an important role in the regulation of the growth pattern in the ring dove.