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

Abstract

The mechanisms by which high salt intake increases vascular resistance in hypertensive humans are not clear. The possibility that salt-loading produces structural changes of the forearm resistance vessels in hypertensive patients was examined. Patients (17) with essential hypertension were given 7 days of 70 meq and 345 meq Na diet. Patients were arbitrarily divided into 2 groups based on blood pressure response to salt-loading: those whose mean blood pressure increased by > 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 > 10% (salt-nonresponsive patients, n = 9). To determine whether there were structural vascular changes of the forearm resistance vessels during salt-loading, maximal vasodilator capacity of the forearm resistance vessels was examined during low and high salt diets by measuring minimal forearm vascular resistance during peak reactive hyperemia following 10 min of arterial occlusion. Salt-loading increased forearm vascular resistance (P < 0.01) and decreased maximal vasodilator capacity (P < 0.01) in salt-responsive patients but did not alter them in salt-nonresponsive patients. Forearm vascular responses to ice on the forehead or to i.v. 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). Apparently, 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 salt-induced increase in forearm vascular resistance.