Plasma Arginine Vasopressin and Serum Copeptin Concentrations at Rest and After Osmotic- and Non-Osmotic-Based Stimulation Tests in Dogs.

Abstract

BACKGROUND: Serum copeptin (sCoP) is used as a surrogate for plasma arginine vasopressin (pAVP) measurement in humans. OBJECTIVE: To measure pAVP and sCoP at rest and after osmotic- and non-osmotic stimulation testing in dogs. ANIMALS: Eight young castrated/spayed healthy research Beagles, eight young intact dogs, and eight old neutered healthy client-owned dogs. METHODS: In this prospective longitudinal study, pAVP and sCoP were measured under iso-(baseline), hypo-(water load followed by intravenous administration of desmopressin [WLT]), and hyper-(water deprivation test [WDT]) osmolar conditions assessed by measured plasma osmolality (pOsm), and after administration of arginine (AST), IV, and Bovril (BST), PO. The fraction of change (F) in a variable y (e.g., pAVP) between baseline (T) and a timepoint X (T) during testing was defined as Fy&#x2009;=&#x2009;[y (T)&#x2009;-&#x2009;y (T)]/y (T). RESULTS: Baseline sCoP had wide inter-individual variations. Mean [range] FpAVP and FsCoP at the end of WDT were +110% [+80; +142] and +18% [+0.4; +38] compared to baseline, respectively. Mean [range] FpAVP after water load and FsCoP after water load followed by desmopressin administration were -22% [-48; -0.5] and -29% [-39; -14] compared to baseline, respectively. Both FpAVP and FsCoP were strongly correlated to FpOsm(r&#x2009;=&#x2009;+0.76, p&#x2009;=&#x2009;0.004; r&#x2009;=&#x2009;+0.78, p&#x2009;=&#x2009;0.002; respectively). When sCoP was measured at Tinstead of Tduring WLT, to reflect its longer half-life reported in humans, the correlation between FpAVPand FsCoP became excellent (r&#x2009;=&#x2009;+0.90, p&#x2009;<&#x2009;0.001). No stimulation of sCoP secretion occurred during AST or BST. CONCLUSION AND CLINICAL IMPORTANCE: Serum CoP could be used as a surrogate for pAVP measurement in healthy dogs.