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(m)), 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 (T0) and a timepoint X (TX) during testing was defined as Fy = [y (TX) – y (T0)]/y (T0). 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(m) (r = +0.76, p = 0.004; r = +0.78, p = 0.002; respectively). When sCoP was measured at T4h instead of T2h during WLT, to reflect its longer half-life reported in humans, the correlation between FpAVPP800 and FsCoP became excellent (r = +0.90, p < 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.