Immunohistochemical studies on the development of avian embryo pituitary corticotrophs under normal and experimental conditions.

Abstract

Immunofluorescent ACTH cells are present in the developing chick pituitary gland from the 9th day of incubation. Rathke pouch grafts from 4–5 day or 5.5 and 6.5 day-old chicks, grafted into chick chorioallantoic membrane and grown for 12 days, gave rise to tinctorially normal pituitary glands in both cases. The early grafts were of pouch epithelium alone, separated from mesenchyme by trypsinization. The later grafts were surrounded by their attached mesenchyme, from which they are virtually inseparable. In 17 out of 18 of the 4.5 day grafts no immunofluorescent ACTH cells developed. (In the 18th case a few feebly stained single cells). In 16 out of 30 of the 5.5 and 6.5 day grafts ACTH cells were present in normal numbers. Of the 3 hypotheses put forward to explain these findings only one appears valid. This is that the ACTH cells are contributed directly by the mesectoderm (neural crest) surrounding the 5.5 and 6.5 day pituitary primordia.