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Glucocorticoid receptors in sheep brain tissues during development
The American Journal of Physiology
|October 1, 1985
Summary
Glucocorticoid receptors are present in fetal sheep pituitary and brain tissues by midgestation. Receptor numbers decrease significantly in adult sheep, with higher concentrations in the pituitary than in the hypothalamus or hippocampus.
Area of Science:
- Endocrinology
- Neuroscience
- Developmental Biology
Background:
- Glucocorticoids play crucial roles in regulating physiological processes, including stress response and development.
- The glucocorticoid receptor (GR) mediates these effects, and its expression and function change throughout development.
- Understanding the developmental trajectory of GRs in key tissues is essential for comprehending glucocorticoid action.
Purpose of the Study:
- To investigate the developmental changes in glucocorticoid binding sites in the pituitary, hypothalamus, and hippocampus of sheep.
- To characterize the presence and quantity of glucocorticoid receptors during fetal, neonatal, and adult stages.
Main Methods:
- Cytosols from sheep pituitary, hypothalamic, and hippocampal tissues at different developmental stages were analyzed.
- Specific binding of [3H]triamcinolone acetonide was measured to quantify glucocorticoid binding sites.
- Sucrose density gradient centrifugation was used to characterize the binding site complex.
Main Results:
- Specific, saturable binding of [3H]triamcinolone acetonide was observed in all tissues studied.
- Glucocorticoid binding sites were present in significant quantities by midgestation (70 days) in pituitary and brain tissues.
- Receptor numbers remained relatively constant through gestation and the neonatal period but declined markedly in adult tissues.
- Pituitary cytosols consistently showed higher binding site concentrations than hypothalamic and hippocampal cytosols across all ages.
- The binding site complex exhibited characteristics of the glucocorticoid receptor.
Conclusions:
- The biochemical machinery for glucocorticoid effects, including the glucocorticoid receptor, is established by midgestation in the fetal pituitary and relevant brain regions.
- Significant developmental changes in glucocorticoid receptor number occur, with a notable decrease in adulthood.
- Tissue-specific differences in receptor abundance exist, with the pituitary having higher levels than the hypothalamus and hippocampus.