Dietary v intravenous salt loading for the assessment of salt sensitivity in normotensive men

The purpose of this study was to compare the blood pressure response to two commonly used protocols for the assessment of salt sensitivity in normotensive men, involving either the rapid intravenous administration of a saline load followed by diuretic-induced salt depletion, or the more physiologic but time-consuming approach involving dietary salt depletion and repletion. Twenty-two healthy male volunteers (22-35 years old) were given a saline load (2 L of 0.9% NaCl over 4 h, i.v.), and on the following day, a low-salt diet (20 mmol NaCl) and furosemide (3 x 40 mg, po). Resting mean arterial blood pressure (MABP) was assessed after the saline load and on the morning following salt depletion. After a 2-week wash-out period, subjects were given a low-salt diet (20 mmol/day NaCl) for 2 weeks, supplemented by either 220 mmol/day NaCl or placebo for 1 week each. At the end of each week, resting MABP was assessed in the supine subjects. Although MABP changes were quite variable (iv, mean -2.1 mm Hg; range, -9.1 to +5.6; diet, mean -2.0 mm Hg; range, -14.3 to +7.2), there was a significant correlation between the salt-induced changes in MABP (r = 0.56, P < .01) and diastolic blood pressure (r = 0.56, P < .01) between the two protocols. However, in individual subjects, blood pressure response to the intravenous protocol did not uniformly predict the blood pressure response to the dietary protocol.(ABSTRACT TRUNCATED AT 250 WORDS)