Venous responses to salt loading in hypertensive subjects.

Abstract

It has been previously suggested that salt loading produces structural changes of the arteries in hypertensive patients who respond to salt loading with a greater rise of blood pressure. This study examined the possibility that salt loading alters venous distensibility in hypertensive patients. Twenty-one patients with essential hypertension were placed on a low-sodium diet (70 meq) for 7 days and then were placed on a high-sodium diet (345 meq) for 7 days. Patients were arbitrarily divided into two groups based on the response of their blood pressure to salt loading: (1) those whose mean blood pressure increased by more than 10% while on the high-salt diet as compared with those on the low-salt diet (salt-responsive patients, n = 8) and (2) those whose mean blood pressure did not increase by more than 10% (salt-nonresponsive patients, n = 13). The venous pressure-volume relationship was determined in the forearm with a water-filled plethysmograph when patients were on the low-and high-salt diet. Venous pressure-volume curves were not different between salt-responsive and salt-nonresponsive patients while on the low-salt diet. High-salt intake shifted the curve toward the pressure axis for salt-responsive patients (p < .05) but not for salt-nonresponsive patients. Phentolamine, 1 mg administered intravenously for 5 min, did not significantly alter venous pressure-volume curves for either group while on the low-or high-salt diet. These results suggest that salt loading decreased venous distensibility in salt-responsive patients, which resulted from nonadrenergic mechanisms: structural changes of the veins could perhaps be included as one of these mechanisms. Circulation 69, No. 1, 50-56, 1984. EPIDEMIOLOGIC STUDIES suggest that an excessive intake of salt contributes to the prevalence of essential hypertension in humans.' However, the mechanisms by which an excessive intake of salt promotes hypertension in humans are not clear.Recent

Impaired microvascular dilatation and capillary rarefaction in young adults with a predisposition to high blood pressure.

“…3), a difference which is similar in magnitude to the 17% rarefaction observed in established hypertension (2), and which could explain the decrease in maximal dermal blood flow. Total peripheral vascular resistance and minimum forearm vascular resistance (principally determined by resistance in skeletal muscle), however, are increased in patients with essential hypertension (16,31) and in their normotensive relatives (41). We found no difference among corners for these variables, albeit that there was a trend towards elevated minimal forearm vascular resistance in nonsmokers in corner OH/PH.…”

Racial and ethnic modifiers of the salt-blood pressure response.

“…Takeshita et al 12 found salt sensitivity in 38% (8/21) of hypertensive Japanese subjects. Salt sensitivity was defined as a rise in mean arterial pressure of greater than 10% after switching from a 70 meq/ day sodium diet to a 345 meq/day sodium diet.…”

Venous distensibility during pregnancy. Comparisons between normal pregnancy and preeclampsia.

“…Previously we have shown that an external pressure of 20 mm Hg was sufficient to collapse the veins under resting conditions. 20 The difference between the pressure within the veins and the external water pressure surrounding them is the distending or transmural pressure. Venous pressure was measured through a polyethylene tube inserted into a superficial vein in the segment of the forearm enclosed in the plethysmograph.…”