title: Changes in plasma copeptin, the c-terminal portion of arginine vasopressin during water deprivation and excess in healthy subjects.
abstract: BACKGROUND
  The measurement of arginine vasopressin (AVP) is often cumbersome because it is unstable with a short half-life time. AVP is derived from a larger precursor peptide along with the more stable peptide copeptin. Copeptin is the C-terminal part of provasopressin and has been shown to be a useful tool to indicate AVP concentration in critically ill patients.
  
  
  OBJECTIVE
  The objective of the study was to evaluate the clinical usefulness of copeptin as a new marker in disordered states of blood volume and plasma osmolality.
  
  
  METHODS
  This was a prospective observational study in a university hospital.
  
  
  METHODS
  Three techniques with respective control studies were used in 24 healthy adults to produce changes in plasma osmolality and/or volume: 1) a 28-h water deprivation, 2) a 17-h hypertonic saline infusion combined with thirsting, and 3) a hypotonic saline infusion with iv desmopressin administration during free water intake.
  
  
  RESULTS
  Water deprivation produced a weight loss of 1.7 kg, an increase in plasma osmolality to 294.8 +/- 4.3 mosmol/kg, and an increase of copeptin from 4.6 +/- 1.7 pmol/liter to 9.2 +/- 5.2 pmol/liter (P < 0.0001). During hypertonic saline infusion and thirsting with a raise of plasma osmolality to 296.1 +/- 3.4 mosmol/kg, copeptin increased from 4.9 +/- 3.0 pmol/liter to 19.9 +/- 4.8 pmol/liter (P < 0.0001). Conversely, during hypotonic saline infusion, plasma osmolality decreased to 271.3 +/- 4.1 mosmol/kg, and copeptin decreased from 6.2 +/- 2.4 pmol/liter to 2.4 +/- 2.1 pmol/liter (P < 0.01).
  
  
  CONCLUSIONS
  Copeptin shows identical changes during disordered water states as previously shown for AVP. It might be a reliable marker of AVP secretion and substitute for the measurement of circulating AVP levels in clinical routine.
authors.affiliation: Division of Endocrinology, Diabetology, and Clinical Nutrition, University Hospital, CH-4031 Basel, Switzerland. gabor.szinnai@unibas.ch
authors.forename: Gabor
authors.initials: G
authors.lastname: Szinnai
authors.forename: Nils G
authors.initials: NG
authors.lastname: Morgenthaler
authors.forename: Kaspar
authors.initials: K
authors.lastname: Berneis
authors.forename: Joachim
authors.initials: J
authors.lastname: Struck
authors.forename: Beat
authors.initials: B
authors.lastname: Müller
authors.forename: Ulrich
authors.initials: U
authors.lastname: Keller
authors.forename: Mirjam
authors.initials: M
authors.lastname: Christ-Crain
mesh_terms: D000328:Adult; D001127:Arginine Vasopressin / Q000097:blood / Q000737:chemistry; D015415:Biomarkers / Q000097:blood*; D001810:Blood Volume / Q000502:physiology; D002624:Chemistry, Clinical / Q000379:methods* / Q000592:standards; D004326:Drinking / Q000502:physiology*; D005260:Female; D006020:Glycopeptides / Q000097:blood*; D006801:Humans; D020896:Hypovolemia / Q000097:blood; D008297:Male; D009994:Osmolar Concentration; D017434:Protein Structure, Tertiary; D015203:Reproducibility of Results; D012964:Sodium / Q000097:blood; D014868:Water Deprivation / Q000502:physiology*
chemical_list: D015415:Biomarkers; D006020:Glycopeptides; C048197:copeptins; D001127:Arginine Vasopressin; D012964:Sodium