EN05 - Plasma Arginine Vasopressin and Serum Copeptin Concentrations Under Hypo-, Iso- and Hyper-osmolar Conditions

Abstract



Background:  Serum copeptin (sCoP), a glycopeptide comprising the C-terminal part of arginine vasopressin (AVP) prohormone, has mostly replaced the measurement of plasma arginine vasopressin (pAVP) in humans for the clinical investigation of specific polyuria-polydipsia disorders.

Objectives: To investigate sCoP as a potential surrogate of pAVP measurement.

Animals: 9 young adult dogs from a research colony.

Methods: Prospective longitudinal study. Serum CoP and pAVP were measured under iso- (baseline), hypo- (water load test [WLT]), and hyper- (modified water deprivation test [MDWT]) osmolar conditions. In the WLT, 9 dogs were given 44 mL/kg of warmed tap water via nasogastric tube over 30 minutes, followed by 0.3 ug/kg IV CRI of desmopressin acetate over 20 minutes; pAVP was collected 2h after and sCoP 4h after tap water administration. In the MDWT, sCoP and pAVP were measured in 8 dogs after either ≥5% body weight loss or a fasting period ≥48h.

Results: Two dogs were excluded from sCoP analyses since serum samples had marked hemolysis, which interfered with optical density readings. Median pAVP was significantly lower after WLT (19.5 pg/mL) vs. baseline (24.2 pg/mL, p = .004). Mean pAVP was significantly higher after MDWT (53.6 pg/mL) vs. baseline (37.9 pg/mL, p = .012). Similarly, mean sCoP was significantly lower after WLT (230 pg/mL) vs. baseline (299 pg/mL, p = .035) and significantly higher after MDWT (335 pg/mL) vs. baseline (280 pg/mL, p = .029). Correlation between pAVP and sCoP was moderately positive (Pearson r = + .52, p = .019).

Conclusion and clinical importance: Serum CoP has the potential to be a sensitive surrogate for pAVP measurement in dogs.