Kinetics of renal sodium excretion during changes in dietary sodium intake in man--an exponential process?
The kinetics of urinary sodium excretion was studied during sodium restriction and sodium supplementation in normal subjects. Eight were studied on a normal sodium intake (24 h urinary sodium: 133.3 + 9.6 mmol) and then during 6 days on a low sodium intake of 10 mmol/day. Six other subjects were studied after equilibration on the low sodium intake for 7 days and then during 5 days on a high sodium intake of 350 mmol/day. 24 h urinary sodium excretion during sodium restriction was consistent with a first-order exponential process with an estimated half-life of 21.8 + 2.4 hours. During sodium supplementation there were corresponding increases in urinary sodium excretion reaching the new steady-state within 3 days but the behaviour of the urinary sodium excretion during the transition period was not consistent with a mono-exponential process. These observations support the concept that the control of sodium balance, during sodium restriction at least, is consistent with a first order proportional feed-back system. This kinetic approach should provide a useful framework for further studies on the dynamics of sodium excretion.
Sagnella
G A
GA
Department of Medicine, Charing Cross & Westminster Medical School, London.
Markandu
N D
ND
Singer
D R
DR
MacGregor
G A
GA
D000293:Adolescent; D000328:Adult; D004039:Diet, Sodium-Restricted; D004305:Dose-Response Relationship, Drug; D005260:Female; D006207:Half-Life; D006801:Humans; D007668:Kidney / Q000378:metabolism*; D008297:Male; D009318:Natriuresis / Q000502:physiology*; D012982:Sodium, Dietary / Q000008:administration & dosage / Q000378:metabolism*
D012982:Sodium, Dietary