SELF-SELECTION OF SALT SOLUTIONS AND WATER BY NORMAL AND HYPERTENSIVE RATS

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Abstract
Rats made hypertensive by enclosing their kidneys in latex rubber capsules were offered water and 0.17 [image] solns. of various salts to determine whether or not the hypertensive state was associated with any change of appetite for specific salts, and whether or not existing hypertension could be modified by self-selection of salts. The mild polydipsia of hypertensive rats was confirmed. When offered "free choice" of various solns., including solns. of NaCl and NaHCO3, hypertensive rats elected to take only 1/3-1/2 as much NaCl and NaHCO3 as did normal rats tested concurrently. This restriction of intake was more striking in moderately hypertensive rats than in those with severe hypertension, but was not complete enough to restore blood pressure to normal. The intakes of Na citrate, Na2SO4, Na2HPO4, KC1, CaCl2 and MgCl2 were quite small and were not detectably different in normal and hypertensive animals. Minute differences in appetite for these salts cannot be excluded, however, due to a "tasting error" when relatively concentrated solns. are offered. Hypertensive rats showed no special appetite for certain salts which have been described as producing temporary alleviation of hypertension, viz., NaSCN, NaNO2, NaI and NH4Cl. All these salts were taken equally and in small amts. by normal and hypertensive rats with no change of blood pressure. NaBr was taken in greater amt. by a few moderately hypertensive rats with lowering of blood pressure secondary to torpor and reduced food intake, but the results were not consistent enough to be really significant. Salts of certain "trace" elements, viz., B, Mn, Co, Li, Sr and Cd were taken in small and approx. equal amts. by normal and hypertensive rats, without significant effects on blood pressure. The consistent and significant reduction of NaCl and NaHCO3 intake by hypertensive rats adds another item of evidence in favor of some as yet unexplained relation between the hypertensive state and Na metabolism. The feasibility of using the self-selection technique in exploring possible metabolic disorders associated with hypertension is discussed.

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