CHANGE IN BLOOD-PRESSURE DURING ALTERED SODIUM-INTAKE IS NOT ASSOCIATED WITH CALCIOTROPIC HORMONE LEVEL

1. We evaluated the effects of the dietary restriction of sodium chlor ide on blood pressure and systemic calcium metabolism in 19 in-patient s with essential hypertension (11 men and 8 women, mean age 49.9 +/- 1 2.1 years). 2. All patients received a high-sodium diet (250 mmol/day) for 1 week, followed by a low-sodium diet (10 mmol/day) for another w eek. Intake of potassium (100 mmol/day) and of calcium (15 mmol/day) w ere kept constant throughout the study. 3. Sodium restriction signific antly reduced the mean blood pressure (from 114.0+/-1.9 to 105.0+/- 13 .7 mmHg, P<0.01). Urinary calcium excretion was significantly reduced (from 5.1 +/- 2.4 to 2.2 +/- 1.0 mmol/day, P < 0.01). 4. The change in mean blood pressure after sodium restriction was not correlated with a change in any parameter of calcium metabolism [whole blood ionized c alcium, plasma intact parathyroid hormone, or 1,25-(OH)(2) vitamin D-3 ]. 5. Plasma renin activity during a regular sodium diet, an index of renin status, was significantly and inversely correlated with the chan ge in blood pressure during sodium restriction, but not with any chang e in the parameters of calcium metabolism. 6. We conclude that sodium restriction reduces blood pressure and decreases urinary calcium excre tion, However, we observed no significant role of extracellular calciu m concentration or of calciotropic hormone concentration in the mechan ism of sodium sensitivity.