Characteristics of responses to salt loading and deprivation in hypertensive subjects.

The mechanisms by which high salt intake increases vascular resistance in hypertensive humans are not clear. This study examined the possibility that salt loading produces structural changes of the forearm resistance vessels in hypertensive patients. Seventeen patients with essential hypertension were given 7 days of 70 mEq and 345 mEq sodium diet. Patients were arbitrarily divided into two groups based on blood pressure response to salt loading: those whose mean blood pressure increased by more than 10% during high salt diet as compared to those on a low salt diet (salt-responsive patients, n = 8) and those who did not increase by more than 10% (salt-nonresponsive patients, n = 9). To determine whether there were structural vascular changes of the forearm resistance vessels during salt loading, we examined maximal vasodilator capacity of the forearm resistance vessels during low and high salt diets by measuring minimal forearm vascular resistance during peak reactive hyperemia following 10 minutes of arterial occlusion. Salt loading increased forearm vascular resistance (P < 0.01) and decreased maximal vasodilator capacity (P < 0.01) in saltresponsive patients but did not alter them in salt-nonresponsive patients. Forearm vascular responses to ice on the forehead or to intravenous phentolamine (10 mg) were augmented (P < 0.01) during the high salt diet in both groups, but more in salt-responsive patients than in salt-nonresponsive patients (P < 0.01). These results are consistent with the view that, in hypertensive patients who responded to salt loading with a greater rise of blood pressure, salt loading produced structural changes of the forearm resistance vessels and structural vascular changes contributed to the saltinduced increase in forearm vascular resistance. (Circ Res 51: 457-464, 1982)