Allopregnanolone in the brain and blood after disruption of the hypothalamic-pituitary-adrenal axis in fetal sheep
| Autor: | Phuong Nguyen, David Walker, I. Ross Young, Jonathan J. Hirst |
|---|---|
| Rok vydání: | 2004 |
| Předmět: |
medicine.medical_specialty
Hypophysectomy Neuroactive steroid Hydrocortisone Endocrinology Diabetes and Metabolism medicine.medical_treatment Immunoblotting Radioimmunoassay Gestational Age Pregnanolone Biology chemistry.chemical_compound Fetus Endocrinology Adrenocorticotropic Hormone Pregnancy Internal medicine Adrenal Glands medicine Animals Cholesterol Side-Chain Cleavage Enzyme Progesterone Brain Chemistry Sheep Adrenal gland Cholesterol side-chain cleavage enzyme Adrenalectomy Allopregnanolone medicine.anatomical_structure chemistry Pituitary Gland Pregnenolone Female Hypothalamic–pituitary–adrenal axis medicine.drug |
| Zdroj: | Journal of Endocrinology. 182:81-88 |
| ISSN: | 1479-6805 0022-0795 |
| DOI: | 10.1677/joe.0.1820081 |
| Popis: | Neuroactive steroids may be synthesised in the brain either de novo from cholesterol or from blood-borne precursors. Concentrations of a GABAA receptor agonist, allopregnanolone, in the fetal brain exceed those in the circulation, and are markedly higher than adult brain concentrations. We used fetal hypophysectomy or adrenalectomy to elucidate the contribution of hypothalamic-pituitary factors and adrenal steroid secretion to the overall neuroactive steroid level in both the fetal brain and the fetal circulation. Hypophysectomy or adrenalectomy was performed between 108 and 112 days of gestation (term approximately 147 days) and fetal tissues were collected at 140 days of gestation. Immunoreactive (ir) ACTH and cortisol in the plasma were significantly reduced after hypophysectomy, whereas adrenalectomy led to increased irACTH but significantly decreased cortisol concentrations, as expected. Brain concentrations of allopregnanolone, progesterone and pregnenolone did not change significantly in fetuses that underwent either hypophysectomy or adrenalectomy; however, concentrations in the plasma and content in the adrenal gland were decreased. Expression of cytochrome P450 scc and 5alpha-reductase type II (5alphaRII) in the brain, measured by western immunoblotting, did not change after either hypophysectomy or adrenalectomy but, after hypophysectomy, expression of P450 scc in the adrenal gland was significantly decreased and that of 5alphaRII remained unchanged. These findings suggest that the regulation of the neuroactive steroid content in the fetal brain is independent of adrenal steroidogenesis and hypothalamic-pituitary factors. Furthermore, the absence of a change in enzyme expression in the brain suggests that the control of the expression of these enzymes is independent of hypothalamic-pituitary factors. Thus local control mechanisms within the brain may be responsible for maintaining the high neurosteroid content present during fetal life, as these mechanisms are independent of adrenal steroid production. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|