title: Ewes With Divergent Cortisol Responses to ACTH Exhibit Functional Differences in the Hypothalamo-Pituitary-Adrenal (HPA) Axis.
abstract: Within any population, the cortisol response to ACTH covers a considerable range. High responders (HRs) exhibit a greater cortisol secretory response to stress or ACTH, compared with individuals classified as low cortisol responders (LRs). We administered ACTH (0.2 μg/kg, iv) to 160 female sheep and selected subpopulations of animals as LR and HR. In the present study, we aimed to characterize the hypothalamo-pituitary-adrenal axis in HR and LR and to identify factors that underlie the differing cortisol responses to ACTH. Hypothalami, pituitaries, and adrenals were collected from nonstressed HR and LR ewes. Expression of genes for CRH, arginine vasopressin (AVP), oxytocin, glucocorticoid receptor, and mineralocorticoid receptor were measured by in situ hybridization in the paraventricular nucleus of the hypothalamus, and proopiomelanocortin (POMC) gene expression was measured in the anterior pituitary. Expression of CRH, AVP, and POMC was higher in HR, with no differences in either glucocorticoid receptor or mineralocorticoid receptor expression. Oxytocin expression was greater in LR. In the adrenal gland, real-time PCR analysis indicated that expression of the ACTH receptor and a range of steroidogenic enzymes was similar in HR and LR. Adrenal weights, the cortex to medulla ratio and adrenal cortisol content were also similar in LR and HR. In conclusion, LR and HR display innate differences in the steady-state expression of CRH, AVP, oxytocin, and POMC, indicating that selection for cortisol responsiveness identifies distinct subpopulations that exhibit innate differences in the gene expression/function of hypothalamo-pituitary-adrenal axis markers.
authors.affiliation: Metabolic Disease and Obesity Program (S.D.H., B.A.H.) and Neuroscience Program (I.J.C., A.R.), Monash Biomedicine Discovery Institute and Department of Physiology, Monash University, Melbourne, Victoria 3800, Australia.
authors.forename: Sakda D
authors.initials: SD
authors.lastname: Hewagalamulage
authors.affiliation: Metabolic Disease and Obesity Program (S.D.H., B.A.H.) and Neuroscience Program (I.J.C., A.R.), Monash Biomedicine Discovery Institute and Department of Physiology, Monash University, Melbourne, Victoria 3800, Australia.
authors.forename: Iain J
authors.initials: IJ
authors.lastname: Clarke
authors.affiliation: Metabolic Disease and Obesity Program (S.D.H., B.A.H.) and Neuroscience Program (I.J.C., A.R.), Monash Biomedicine Discovery Institute and Department of Physiology, Monash University, Melbourne, Victoria 3800, Australia.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Rao
authors.affiliation: Metabolic Disease and Obesity Program (S.D.H., B.A.H.) and Neuroscience Program (I.J.C., A.R.), Monash Biomedicine Discovery Institute and Department of Physiology, Monash University, Melbourne, Victoria 3800, Australia.
authors.forename: Belinda A
authors.initials: BA
authors.lastname: Henry
mesh_terms: D000311:Adrenal Glands / Q000378:metabolism; D000324:Adrenocorticotropic Hormone / Q000502:physiology*; D000818:Animals; D001127:Arginine Vasopressin / Q000378:metabolism; D003346:Corticotropin-Releasing Hormone / Q000378:metabolism; D005260:Female; D006854:Hydrocortisone / Q000097:blood / Q000378:metabolism*; D007030:Hypothalamo-Hypophyseal System / Q000502:physiology*; D009765:Obesity / Q000209:etiology*; D010121:Oxytocin / Q000378:metabolism; D010913:Pituitary-Adrenal System / Q000502:physiology*; D011333:Pro-Opiomelanocortin / Q000378:metabolism; D011965:Receptors, Glucocorticoid / Q000378:metabolism; D018161:Receptors, Mineralocorticoid / Q000378:metabolism; D012756:Sheep
chemical_list: D011965:Receptors, Glucocorticoid; D018161:Receptors, Mineralocorticoid; D001127:Arginine Vasopressin; D010121:Oxytocin; D011333:Pro-Opiomelanocortin; D000324:Adrenocorticotropic Hormone; D003346:Corticotropin-Releasing Hormone; D006854:Hydrocortisone