The effect of long-term oral
sodium loading on blood pressure and on stress-induced cardiovascular response was studied in normotensive and marginally hypertensive young adults. The 121 subjects, 18-23 years old, included 38 whites and 83 blacks. Blood pressure and heart rate response to the stress of mental arithmetic was measured before and after 14 days of
sodium load, which consisted of 10 g NaCl/day added to the usual diet. A
sodium-sensitive response to
sodium load occurred in 18.4% of whites and 37.3% of blacks.
Sodium-insensitive subjects had a higher rate of
sodium excretion (p less than 0.001).
Sodium-sensitive hypertensive subjects had a significantly greater
weight gain (p less than 0.001). A significant correlation between blood pressure change and
sodium excretion (r = -0.28, p less than 0.01) occurred in the
sodium-sensitive group. The high
sodium intake did not augment the blood pressure or heart rate response to the beta-
adrenergic-mediated stimulus of mental arithmetic in the population when grouped by blood pressure, race, or
sodium sensitivity. These results suggest that blood pressure increase in response to
sodium load, particularly in blacks, is related to functional changes in peripheral vascular resistance.