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Effect of dietary salt restriction on urinary serotonin and 5-hydroxyindoleacetic acid excretion in man
A M Sharma1, U Schorr, H M Thiede
1Department of Internal Medicine, Universitätsklinikum Steglitz, Free University of Berlin, Germany.
Objective:
To determine the effect of dietary salt restriction on urinary excretion of serotonin and its principal metabolite 5-hydroxyindoleacetic acid (5-HIAA) in man.
Design:
We studied 16 healthy male volunteers (age range 20-28 years) who ate a standard diet containing 20 mmol/day NaCl, to which either 220 mmol/day NaCl or placebo was added as a supplement for 1 week each, according to a randomized, single-blind crossover design.
Methods:
Urinary excretion of serotonin, 5-HIAA, noradrenaline and vanillylmandelic acid (VMA) were measured during the low- and high-salt periods using reverse-phase high-performance liquid chromatography.
Results:
During the low-salt diet, 24-h urinary excretion of serotonin increased by 42%, accompanied by a 52% rise in the excretion of 5-HIAA. Salt restriction also increased noradrenaline excretion by 77% and VMA excretion by 40%. Regression analysis revealed a strong positive relationship between the excretion of serotonin and of noradrenaline (r = 0.84, P < 0.001) and between that of 5-HIAA and of VMA (r = 0.74, P < 0.001).
Conclusions:
Salt restriction stimulates the serotonergic system in man. Stimulation of this system, in conjunction with the sympathetic nervous system, may contribute to renal sodium conservation during dietary salt restriction in man.