Glucocorticoid receptors in sheep brain tissues during development.

In this study we describe changes in the number of glucocorticoid binding sites that occur in cytosols of pituitary, hypothalamic, and hippocampal tissue obtained from fetal, newborn, and adult sheep. We observed specific, saturable binding of [3H]triamcinolone acetonide by cytosols of all three tissues. There were both age-related and tissue-related differences in the number of binding sites observed. By midgestation (70 days) significant quantities of binding sites were present in pituitary and brain tissues, and the number remained relatively constant throughout gestation and in the neonatal period. The number of binding sites declined markedly in cytosols from adult tissues. At all ages there were more binding sites present in pituitary cytosols than in cytosols of hypothalamus and hippocampus. The sucrose density gradient profile of the radioactive ligand-binding site complex is characteristic of a glucocorticoid receptor. Thus, by midgestation at least a portion of the biochemical machinery mediating glucocorticoid effects is present in the fetal pituitary and in specific brain tissues considered important in the modulation of ACTH secretion by corticosteroids.