Sodium and potassium intake and blood pressure.

Sodium and potassium intakes were increased in normotensive volunteers to assess the effects on their blood pressures. An approximately threefold increase in sodium intake for eight days had no effect on the blood pressures of seven volunteers, while a two-stage increase in potassium intake, by about 40% for eight days and a further 55% for 14 days, had no effect on the blood pressures of 21 volunteers. Renal electrolyte excretions and the blood pressures of all 28 subjects showed no statistically significant correlations between either sodium or potassium excretion and blood pressure. A weak negative correlation was found between the sodium: potassium ratio and systolic pressure. The small reductions in sodium intake and increases in potassium intake that might be achieved through propaganda and changes in food processing are unlikely to lower mean blood pressure in Western societies.     

Sodium intake influences the effects of atriopeptin on blood pressure and transcapillary fluid shift in the rat

The influence of chronic changes in sodium intake on the acute effects of atrial natriuretic peptide (ANP) on arterial pressure and fluid translocation was assessed in acutely binephrectomized rats. After 3 weeks of either low sodium or high sodium diet, animals were administered ANP at doses of 0.1 and 1 microgram/kg/min. A marked and irreversible hypotensive response to ANP was observed with the higher infusion rate in the low sodium group, whereas blood pressure did not change significantly in the other groups. The effect of ANP on plasma protein concentration was less marked than that on hematocrit in all groups and was not significantly affected by sodium intake. The effect of both doses of ANP on hematocrit was enhanced in the high sodium group, indicating that the fluid shift out of the intravascular compartment was magnified by high sodium intake.     

Role of potassium in regulating blood flow and blood pressure

Unlike sodium, potassium is vasoactive; for example, when infused into the arterial supply of a vascular bed, blood flow increases. The vasodilation results from hyperpolarization of the vascular smooth muscle cell subsequent to potassium stimulation by the ion of the electrogenic Na+-K+ pump and/or activating the inwardly rectifying Kir channels. In the case of skeletal muscle and brain, the increased flow sustains the augmented metabolic needs of the tissues. Potassium ions are also released by the endothelial cells in response to neurohumoral mediators and physical forces (such as shear stress) and contribute to the endothelium-dependent relaxations, being a component of endothelium-derived hyperpolarization factor-mediated responses. Dietary supplementation of potassium can lower blood pressure in normal and some hypertensive patients. Again, in contrast to NaCl restriction, the response to potassium supplementation is slow to appear, taking approximately 4 wk. Such supplementation reduces the need for antihypertensive medication. "Salt-sensitive" hypertension responds particularly well, perhaps, in part, because supplementation with potassium increases the urinary excretion of sodium chloride. Potassium supplementation may even reduce organ system complications (e.g., stroke).     

Sodium and potassium in essential hypertension.

A study was carried out of arterial pressure and body content of electrolytes in 91 patients with essential hypertension and 121 normal controls. Exchangeable sodium was found to be positively correlated with arterial pressure in the patients, the correlation being closest in older patients; values of exchangeable sodium were subnormal in young patients; and plasma, exchangeable, and total body potassium correlated inversely with arterial pressure in the patients, the correlations being closest in young patients. Three hypotheses were proposed to explain the mechanisms relating electrolytes and arterial pressure in essential hypertension--namely, a cell-salt hypothesis, a dietary salt hypothesis, and a kidney-salt hypothesis. It was concluded that two mechanisms probably operate in essential hypertension. In the early stages of the disease blood pressure is raised by an abnormal process related more closely to potassium than to sodium. A renal lesion develops later, possibly as a consequence of the hypertension. This lesion is characterised by resetting of pressure natriuresis and is manifest by an abnormal relation between body sodium and arterial pressure and by susceptibility to increased dietary sodium intake.     

Chronobiology of blood pressure in childhood: implications for tracking

Chronobiology, in its methodological evolution, developed data series analyses paying particular attention to blood pressure (BP), because of the importance of this biorhythmic variable for assessing the risk of developing hypertension. An example of the potentiality of the chronobiologic procedures is given in the present report which deals with the inferential analysis of the BP 24-h patterns in 3-12 year-old children. By using the chronobiologic methodology, time-qualified standards for BP are calculated. Rhythmometric parameters for circadian rhythm of systolic and diastolic components of BP are also computed. Data presented are a tangible outcome for emphasizing the introduction of chronobiology in epidemiology and pediatrics in order to optimize the primary prevention and care of hypertension taking as reference the chronobiologic standards of BP.     

Sodium and potassium content and membrane transport properties in red blood cells from newborn puppies

The intracellular sodium and potassium concentrations and membrane transport properties for these ions were investigated in red blood cells from newborn puppies and adult dogs. At birth the intracellular concentrations of sodium and potassium are much higher than those found in adult dog red cells. During the first few weeks of life the intracellular concentrations of these ions gradually decrease until the adult level is reached. Changes in the membrane transport properties develop concurrently. The rate of active potassium influx, as measured by ouabain-sensitivity, and the pump to leak ratio are greater in red cells from newborn puppies than in those from adult animals. No ouabain-sensitive sodium efflux could be demonstrated in red cells from older puppies or adult dogs. When either puppy or adult dog red cells are depleted of ATP (by incubation at 37°C with no substrate), potassium permeability increases, and the permeability of the membrane to sodium decreases. The addition of adenosine reverses the effect of depletion.     

Does change in blood pressure predict heart disease?

Whether a change in blood pressure is related to the occurrence of cardiovascular disease, independent of blood pressure level, was investigated using data collected in the Framingham heart study on 5209 subjects. The follow up period of 26 years was divided into a first period of 12 years in which the blood pressure change was computed for each individual and a subsequent period of 14 years in which the risk of cardiovascular disease was determined. Blood pressure change was positively related to risk of cardiovascular disease. This association remained when blood pressure level at the start of the study was taken into account but disappeared when the level attained after the first 12 years was taken into consideration. For the clinician this suggests that the decision to treat high blood pressure is best guided by the actual level of pressure and not by its long term trend in the past.     

High-sodium intake prevents pregnancy-induced decrease of blood pressure in the rat

Despite an increase of circulatory volume and of renin-angiotensin-aldosterone system (RAAS) activity, pregnancy is paradoxically accompanied by a decrease in blood pressure. We have reported that the decrease in blood pressure was maintained in pregnant rats despite overactivation of RAAS following reduction in sodium intake. The purpose of this study was to evaluate the impact of the opposite condition, e.g., decreased activation of RAAS during pregnancy in the rat. To do so, 0.9% or 1.8% NaCl in drinking water was given to nonpregnant and pregnant Sprague-Dawley rats for 7 days (last week of gestation). Increased sodium intakes (between 10- and 20-fold) produced reduction of plasma renin activity and aldosterone in both nonpregnant and pregnant rats. Systolic blood pressure was not affected in nonpregnant rats. However, in pregnant rats, 0.9% sodium supplement prevented the decreased blood pressure. Moreover, an increase of systolic blood pressure was obtained in pregnant rats receiving 1.8% NaCl. The 0.9% sodium supplement did not affect plasma and fetal parameters. However, 1.8% NaCl supplement has larger effects during gestation as shown by increased plasma sodium concentration, hematocrit level, negative water balance, proteinuria, and intrauterine growth restriction. With both sodium supplements, decreased AT1 mRNA levels in the kidney and in the placenta were observed. Our results showed that a high-sodium intake prevents the pregnancy-induced decrease of blood pressure in rats. Nonpregnant rats were able to maintain homeostasis but not the pregnant ones in response to sodium load. Furthermore, pregnant rats on a high-sodium intake (1.8% NaCl) showed some physiological responses that resemble manifestations observed in preeclampsia.     

The effects of protein intake on blood pressure and cardiovascular disease

PURPOSE OF REVIEW: Investigators, especially those from western countries, have commonly assumed that there is either no association or a direct association of protein intake with elevated blood pressure and atherosclerosis. In contrast, recent observational studies and clinical trials have suggested that increased protein intake, particularly protein from plant sources, might actually reduce blood pressure and prevent cardiovascular disease. RECENT FINDINGS: In epidemiological studies, an increased intake of protein has been associated with lower blood pressure and an attenuated increase in blood pressure over time. Furthermore, such studies also suggest that the beneficial effects of increased protein intake result from an increased consumption of protein from plant rather than animal sources. In several predominantly small trials, an increased intake of soy protein lowered blood pressure. With respect to clinical outcomes, reports from large cohort studies suggest that increased protein intake is associated with a reduced risk of ischemic heart disease and perhaps intraparenchymal hemorrhage. In other reports, a higher protein intake is one characteristic of a dietary pattern associated with a reduced risk of ischemic heart disease. The mechanisms by which protein could exert its beneficial effects include an increased intake of biologically active amino acids, peptides, or highly correlated nutrients. SUMMARY: Recent evidence suggests that an increased intake of protein, particularly plant protein, may lower blood pressure and reduce the risk of cardiovascular disease. However, the data are not sufficiently compelling to advocate an increased consumption of protein.