title: Arginine vasopressin and osmolality in the elderly.
abstract: OBJECTIVE
  To evaluate the influence of age on plasma arginine vasopressin (AVP) concentrations and the relationship between plasma AVP and serum osmolality in younger and older subjects, and in the elderly, to assess the effect of gender on plasma AVP concentration and to determine the impact of prostaglandin blockade on renal responsiveness to AVP.
  
  
  METHODS
  Cross-sectional study; randomized, double-blind, crossover, placebo-controlled study.
  
  
  METHODS
  The Renal Laboratory, Royal North Shore Hospital (younger adults) and Clinical Room, St Vincents Hospital (elderly subjects).
  
  
  METHODS
  45 younger adults (35 +/- 9 years), and 41 elderly subjects (29 males, 12 females; 78 +/- 3 years). All subjects were healthy and non-institutionalized. The elderly subjects were screened to exclude significant pathology (clinical assessment, multiple investigations).
  
  
  METHODS
  Blood samples were drawn from all younger and elderly subjects. The elderly subjects were randomly allocated indomethacin or placebo for 1 month. Following a 1 to 2-week washout, the alternative was administered for a further 1 month.
  
  
  METHODS
  Plasma AVP and serum osmolality and plasma AVP, serum, and urine osmolality at baseline were measured on indomethacin and placebo.
  
  
  RESULTS
  In the elderly subjects, baseline plasma AVP concentration was significantly higher than in the younger subjects studied (4.7 +/- 0.7 vs 2.1 +/- 0.2 pg/mL respectively; P = 0.0003). Plasma AVP was strongly correlated with serum osmolality in the younger subjects (r = 0.76, P = 0.0001) but not in the elderly cohort (r = -0.18, P = 0.26). No difference was found between the sexes in plasma AVP (P = 0.89), and indomethacin treatment did not alter the plasma AVP/urine osmolality ratio (P = 0.85) in the elderly subjects. In addition, changes in plasma AVP with indomethacin therapy did not correlate with changes in serum osmolality (r = 0.16, P = 0.09).
  
  
  CONCLUSIONS
  Aging is accompanied by an increase in plasma AVP concentrations. In healthy, elderly subjects, plasma AVP is not dependent on serum osmolality and is not influenced by gender. Indomethacin has no effect on the renal responsiveness to plasma AVP.
authors.affiliation: Department of Clinical Pharmacology and Toxicology, St Vincents Hospital, Darlinghurst, NSW, Australia.
authors.forename: A G
authors.initials: AG
authors.lastname: Johnson
authors.forename: G A
authors.initials: GA
authors.lastname: Crawford
authors.forename: D
authors.initials: D
authors.lastname: Kelly
authors.forename: T V
authors.initials: TV
authors.lastname: Nguyen
authors.forename: A Z
authors.initials: AZ
authors.lastname: Gyory
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000375:Aging / Q000097:blood* / Q000652:urine; D001127:Arginine Vasopressin / Q000097:blood* / Q000187:drug effects; D003430:Cross-Sectional Studies; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007213:Indomethacin / Q000494:pharmacology; D007668:Kidney / Q000187:drug effects; D008297:Male; D008875:Middle Aged; D009994:Osmolar Concentration; D012737:Sex Factors; D014882:Water-Electrolyte Balance / Q000187:drug effects / Q000502:physiology*
chemical_list: D001127:Arginine Vasopressin; D007213:Indomethacin