title: Sodium kinetics in salt-sensitive and salt-resistant normotensive and hypertensive subjects.
abstract: OBJECTIVE
  To test the hypotheses that sodium kinetics are not affected by blood pressure, salt sensitivity, salt resistance or race, and that the kinetics of sodium balance are not a first-order process. DESIGN, PARTICIPANTS AND INTERVENTIONS: Two studies were conducted. In the first, 18 normotensive and 36 hypertensive men and women were given sodium at 120 mmol/day for 6 days, followed by 10 mmol/day for 8 days, then 400 mmol/day for 8 more days. Salt sensitivity was defined as an increase in diastolic blood pressure from the 10 to the 400 mmol/day intake. Salt resistance was defined as no increase, or a decrease in diastolic blood pressure with the increased sodium intake. In the second study, 12 white and 12 black normotensive men ingested sodium at 10, 200 or 400 mmol/day in random order, each for 7 days. All urine was collected in both protocols.
  
  
  METHODS
  Metabolic ward at the University of Greifswald (Greifswald, Germany; study 1), and Clinical Research Center (Indiana University, Indianapolis, Indiana, USA; study 2).
  
  
  METHODS
  In addition to conventional statistics, a pharmacokinetic analysis was carried out to determine the elimination rate constant and half-life.
  
  
  RESULTS
  In the Greifswald study, when the sodium intake was decreased, a longer half-life was determined for the salt-sensitive than the salt-resistant hypertensive subjects. The half-life for the normotensive salt-sensitive and salt-resistant subjects did not differ. When the sodium intake was decreased, a monoexponential equation fitted the data for all subjects; when the sodium intake was increased, only data for half the subjects could be fitted to the same equation. In the Indianapolis study, black race had a significant influence upon urinary sodium excretion. Furthermore, the half-life for sodium elimination was dependent upon sodium intake; namely, the greater the intake, the longer the elimination half-life.
  
  
  CONCLUSIONS
  The time required to reach sodium balance may increase following salt-sensitive increases in blood pressure rather than precede them. Race influences the time required to achieve salt balance. Sodium kinetics are not a first-order process.
authors.affiliation: Department of Internal Medicine, Ernst-Moritz-Arndt University, Greifswald, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Wedler
authors.forename: M E
authors.initials: ME
authors.lastname: Brier
authors.forename: M
authors.initials: M
authors.lastname: Wiersbitzky
authors.forename: S
authors.initials: S
authors.lastname: Gruska
authors.forename: E
authors.initials: E
authors.lastname: Wolf
authors.forename: R
authors.initials: R
authors.lastname: Kallwellis
authors.forename: G R
authors.initials: GR
authors.lastname: Aronoff
authors.forename: F C
authors.initials: FC
authors.lastname: Luft
mesh_terms: D000328:Adult; D044383:Black People; D001794:Blood Pressure / Q000502:physiology; D005260:Female; D006207:Half-Life; D006801:Humans; D006973:Hypertension / Q000208:ethnology / Q000378:metabolism*; D008297:Male; D009318:Natriuresis; D012982:Sodium, Dietary / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000494:pharmacology; D013997:Time Factors
chemical_list: D012982:Sodium, Dietary