Blood pressure, fluid compartments and utilization of chloride in rats fed various chloride diets

The effects of various levels and types of dietary chloride salts on blood pressure were examined in three studies. Weanling Sprague-Dawley rats were fed semipurified diets that contained moderate (1.9 mg Cl/g diet) and supplemental (15.6 mg Cl/g diet) chloride as NaCl, KCl, lysine monohydrochloride with or without CaCO3, or MgCl2 for 56 or 119 d. Rats fed excess chloride excreted more than 84% of the chloride in urine, excreted increased urine volumes (from 3 to 7 wk), tended to consume more fluids (especially if NaCl was fed), had significantly increased blood pressure (7 and 13 wk), had hypertrophied kidneys (8 and 17 wk) and had altered levels of sodium and potassium in their kidneys (17 wk), but experienced no changes in the size of fluid compartments, such as plasma volume or bromine space. Altogether, 56% of the variance in blood pressure measurements at wk 7 could be predicted on the basis of urinary chloride excretion during wk 7 and kidney weight as a percentage of body weight and kidney sodium concentration, but only 30% of the variance in blood pressure measurements at wk 16 could be predicted on the basis of urinary chloride excretion during wk 16 and kidney sodium concentrations.