title: Glucocorticoid receptor density and binding affinity in healthy horses and horses with systemic inflammatory response syndrome.
abstract: BACKGROUND
  Dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis occurs in horses with systemic inflammatory response syndrome (SIRS). Peripheral resistance to glucocorticoids has not been investigated in horses.
  
  
  OBJECTIVE
  To determine if glucocorticoid receptor (GR) function in horses can be measured using flow cytometry, and to use this information to evaluate HPA axis dynamics.
  
  
  METHODS
  Eleven healthy adult horses in parts 1 and 2. Ten horses with SIRS and 10 age and sex matched controls in part 3.
  
  
  METHODS
  Flow cytometry was used to evaluate GR density and binding affinity (BA) in 3 healthy horses in part 1. In part 2, exogenous ACTH was administered to eight healthy horses. Their cortisol response and GR properties were measured. In part 3, CBC, serum biochemistry, cortisol and ACTH, and GR properties were compared between controls without SIRS (n = 10) and horses with SIRS (n = 10), and between survivors and nonsurvivors (n = 4 and n = 6 respectively).
  
  
  RESULTS
  Flow cytometry can be used to measure GR properties in equine PBMCs. No correlation was observed between plasma cortisol concentration and GR density or BA in healthy horses (r = -0.145, P = .428 and r = 0.046, P = .802 respectively). Nonsurvivors with SIRS had significantly decreased GR BA (P = .008). Horses with triglyceride concentration > 28.5 mg/dL had increased odds of nonsurvival (OR=117; 95% CI, 1.94-7,060). GR BA <35.79% was associated with nonsurvival (OR = 30.33; 95% CI, 0.96-960.5).
  
  
  CONCLUSIONS
  Tissue resistance to glucocorticoids contributes to HPA axis dysfunction in adult horses with SIRS. These horses might benefit from treatment with exogenous glucocorticoids.
authors.affiliation: Marion duPont Scott Equine Medical Center, Virginia/Maryland Regional College of Veterinary Medicine, Leesburg, VA.
authors.forename: C J
authors.initials: CJ
authors.lastname: Hoffman
authors.forename: H C
authors.initials: HC
authors.lastname: McKenzie
authors.forename: M O
authors.initials: MO
authors.lastname: Furr
authors.forename: A
authors.initials: A
authors.lastname: Desrochers
mesh_terms: D000324:Adrenocorticotropic Hormone / Q000494:pharmacology; D000818:Animals; D016638:Critical Illness; D005434:Flow Cytometry; D006734:Horse Diseases / Q000378:metabolism*; D006736:Horses; D006854:Hydrocortisone / Q000378:metabolism; D007030:Hypothalamo-Hypophyseal System / Q000502:physiology; D007963:Leukocytes, Mononuclear / Q000378:metabolism*; D010913:Pituitary-Adrenal System / Q000502:physiology; D011485:Protein Binding; D011965:Receptors, Glucocorticoid / Q000235:genetics / Q000378:metabolism*; D018746:Systemic Inflammatory Response Syndrome / Q000378:metabolism / Q000662:veterinary*
chemical_list: D011965:Receptors, Glucocorticoid; D000324:Adrenocorticotropic Hormone; D006854:Hydrocortisone
keywords: Cortisol; Critical illness-related corticosteroid insufficiency; Equine; Glucocorticoid receptor; Systemic inflammatory response syndrome
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