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Combined hypervolemia and hypoosmolality alter hypothalamic-pituitary-adrenal axis response to endotoxin stimulation
F Dadoun1, J G Velut, V Guillaume
1Laboratoire de Neuroendocrinologie Expérimentale, INSERM U 501, Institut Fédératif Jean-Roche, Faculté de Médecine, Hôpital Nord, Marseille, France.
Neuroendocrinology
|May 27, 1999
Summary
Body fluid changes, like hypoosmolality and hypervolemia, blunt stress responses. This study shows that reduced ACTH and cortisol secretion during endotoxin stimulation involves both magnocellular and parvocellular neurons in the PVN.
Area of Science:
- Neuroendocrinology
- Physiology
Background:
- Body fluid disturbances affect corticotropin (ACTH) and glucocorticoid secretion, often linked to arginine vasopressin (AVP) from magnocellular neurons.
- Endotoxin stimulation activates the pituitary-adrenal axis, involving corticotropin-releasing hormone (CRH) and AVP release.
Purpose of the Study:
- To investigate how altered body fluid status (osmolality and volemia) affects the ACTH and glucocorticoid response to endotoxin.
- To elucidate the roles of magnocellular and parvocellular neurons in the paraventricular nucleus (PVN) during these responses.
Main Methods:
- Sheep were subjected to endotoxin stimulation after manipulation of body fluid status via dDAVP and glucose infusion.
- Measurements included CRH, AVP, ACTH, and cortisol levels in portal and peripheral blood.
Main Results:
- Volume loading and plasma dilution significantly blunted ACTH and cortisol responses to endotoxin.
- A parallel decrease in portal CRH and jugular/portal AVP levels was observed in volume-loaded animals.
Conclusions:
- Hypoosmolality and/or hypervolemia reduce the ACTH and cortisol response to endotoxin-induced stress in sheep.
- This blunted response involves not only magnocellular AVP-secreting neurons but also PVN parvocellular neurons co-secreting CRH and AVP.