DIETARY NU-INTRAVENOUS SALT LOADING FOR THE ASSESSMENT OF SALT SENSITIVITY IN NORMOTENSIVE MEN

The purpose of this study was to compare the blood pressure response t o two commonly used protocols for the assessment of salt sensitivity i n normotensive men, involving either the rapid intravenous administrat ion of a saline load followed by diuretic-induced salt depletion, or t he more physiologic but time-consuming approach involving dietary salt depletion and repletion. Twenty-two healthy male volunteers (22-35 ye ars old) were given a saline load (2 L of 0.9% NaCl over 4 h, iv), 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 assess ed 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 (2 0 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 var iable (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 t he 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 in dividual subjects, blood pressure response to the intravenous protocol did not uniformly predict the blood pressure response to the dietary protocol. Thus, despite a modest correlation between the changes in bl ood pressure induced by the two protocols, the value of the infusion p rotocol for the identification of individuals who respond with a chang e in blood pressure to dietary salt restriction appears limited.