AJP - Regulatory, Integrative and Comparative Physiology, Vol 261, Issue 3 603-R608, Copyright © 1991 by American Physiological Society

ARTICLES

Selective effects of sodium and chloride depletion on salt appetite in rats

M. Muntzel, B. Pouzet, B. Lacour, T. Hannedouche and T. Drueke
Institute National de la Sante et de la Recherche Medicale, Department of Nephrology, Hopital Necker, Paris, France.

Findings from hypertension research indicate that dietary sodium chloride (NaCl), Na+, and Cl- independently influence blood pressure, electrolyte metabolism, and hormone secretion. In this context, we examined the effects of NaCl, Na+, and Cl- depletion, respectively, on the development of saline preference (salt appetite) in rats. Male Wistar rats were given a normal diet (1% NaCl) for 15 days and tested for salt appetite using a two-bottle choice test, one bottle containing water and the other 0.3 M saline. The animals were then divided into three groups (n = 11/group): one group received low NaCl, another received a Na(+)-deficient, normal-Cl-diet (low Na+), and a third received a Cl(-)-deficient, normal-Na+ diet (low Cl-). Salt appetite was again tested after 19 days on these diets. Both NaCl and Na+ depletion stimulated saline intake (P less than 0.01), whereas salt appetite did not change in the low-Cl- group. Water intake was not influenced by the regimens. In addition, no alterations were noted for weight, systolic blood pressure, plasma Na+ concentration, or blood pH. Dietary Cl-depletion, however, significantly reduced plasma Cl- concentration (P less than 0.05), and reduced plasma potassium in relation to rats depleted in Na+ (P less than 0.05). Plasma renin activity and urinary aldosterone were elevated in low-NaCl and Na(+)-depleted rats relative to the Cl(-)-depleted group (P less than 0.05). These results suggest that salt appetite is increased by dietary Na+ deficiency but not by Cl- deficiency. Salt appetite may be controlled by central or peripheral systems specifically sensitive to Na+ or by hormonal changes characteristic of Na+ depletion, such as the activation of renin and aldosterone observed in the low-NaCl and low-Na+ groups.