Sodium and potassium in essential hypertension

Association of some biochemical parameters and blood pressure among males with hypertension in the camps of Nineveh province-Iraq

BACKGROUND

Hypertension is a significant public health problem that affects people all over the world. Various epidemiologic researches have been conducted to reveal the relationship between hypertension and several biochemical markers. The goal of this project was to investigate the electrolytes, glucose, total protein, and lipid profile in people with normal and high blood pressure.

MATERIALS AND METHODS

Between 2020 and 2022, a case-control study was done. Two hundred and eighteen males, age ranging from 30 to 70, took part in the study. The conventional flame photometric method was used to evaluate serum electrolytes, whereas kits from Biolab Company's kits were used to quantify serum calcium, serum glucose, and lipid profile.

RESULTS

When compared to normotension males, hypertension males had considerably greater salt, chloride, and potassium levels in their blood, but no significant variations in calcium levels. When compared to normotension males, hypertension individuals had considerably higher mean glucose, total cholesterol, low, and high-density lipoprotein cholesterol, and triglycerides. Many amino acids were identified in the blood of male hypertension patients, consisting of leucine, aspartic acid, glutamic acid, asparagine, serine, histidine, glycine, arginine, alanine, methionine, valine, and phenylalanine.

CONCLUSIONS

In this group, hypertension males have a different lipid and electrolyte profile than normotensive males.

The Hyponatremia Epidemic: A Frontier Too Far?

Hyponatremia is the most common electrolyte abnormality and is often neglected, especially in elderly and seemingly terminal patients. Hyponatremia can be asymptomatic or can cause symptoms ranging from nausea and lethargy to convulsions and coma. This condition has become increasingly common over time with a similar time course to the increase in adoption of low salt diets. The popularization of low salt may not be justified in people with normal kidney function in whom the compatible statistically based evidence that salt causes hypertension has been challenged by experimental evidence to the contrary.

Potassium: From Physiology to Clinical Implications

BACKGROUND

Potassium (K(+)) is the major intracellular cation, with 98% of the total pool being located in the cells at a concentration of 140-150 mmol/l, and only 2% in the extracellular fluid, where it ranges between 3.5 and 5 mmol/l. A fine regulation of the intracellular-extracellular gradient is crucial for life, as it is the main determinant of membrane voltage; in fact, acute changes of K(+) plasma levels may have fatal consequences.

SUMMARY

An integrated system including an 'internal' and 'external' control prevents significant fluctuations of plasma levels in conditions of K(+) loading and depletion. The internal control regulates the intra-extracellular shift, a temporary mechanism able to maintain a constant K(+) plasma concentration without changing the total amount of body K(+). The external control is responsible for the excretion of the ingested K(+), and it has the kidney as the major player. The kidney excretes nearly 90% of the daily intake. Along the proximal tubule and the thick ascending limb on Henle's loop, the amount of K(+) reabsorption is quite fixed (about 80-90%); conversely, the distal nephron has the ability to adjust K(+) excretion in accordance with homeostatic needs. The present review analyzes: (1) the main molecular mechanisms mediating K(+) reabsorption and secretion along the nephron; (2) the pathophysiology of the principal K(+) derangements due to renal dysfunction, and (3) the effect of ingested K(+) on blood pressure and renal electrolyte handling.

KEY MESSAGES

Maintaining plasma K(+) levels in a tight range is crucial for life; thus, multiple factors are implicated in K(+) homeostasis, including kidney function. Recent studies have suggested that K(+) plasma levels, in turn, affect renal salt absorption in animal models; this effect may underlie the reduction of blood pressure observed in hypertensive subjects under K(+) supplementation.

The impact of sodium and potassium on hypertension risk

The pathogenic role of sodium surfeit in primary hypertension is widely recognized but that of potassium deficiency usually has been ignored or at best assigned subsidiary status. Weighing the available evidence, we recently proposed that the chief environmental factor in the pathogenesis of primary hypertension and the associated cardiovascular risk is the interaction of the sodium surfeit and potassium deficiency in the body. Here, we present the major evidence highlighting the relationship between high-sodium intake and hypertension. We then examine the blood pressure-lowering effects of potassium in conjunction with the pernicious impact of potassium deficiency on hypertension and cardiovascular risk. We conclude with summarizing recent human trials that have probed the joint effects of sodium and potassium intake on hypertension and its cardiovascular sequelae. The latter studies lend considerable fresh support to the thesis that the interaction of the sodium surfeit and potassium deficiency in the body, rather than either disturbance by itself, is the critical environmental factor in the pathogenesis of hypertension.

Serum Sodium and Potassium Levels in Cerebro-vascular Accident Patients

BACKGROUND

We aim to assess serum sodium and potassium levels in patients with different types of cerebro-vascular accidents (CVA) in comparison to control group.

METHODS

A comparative cross-sectional study conducted on patients admitted to the emergency department from January to August 2012. Control group consisted of patients admitted to emergency department due to common cold, urinary tract infection, low back pain, cluster, and tension headache or migraine. Serum sodium and potassium levels were measured via standard laboratory methods.

RESULTS

There were 77 patients in control group and 78 in CVA group. Forty nine patients from the CVA group had ischemic CVA, 11 had hemorrhagic CVA and 18 suffered a transient ischemic attack (TIA). Serum sodium level in control group was significantly lower than in patients with TIA, ischemic CVA, and hemorrhagic CVA (P < 0.001). Serum potassium level in control group was higher than patients with TIA, ischemic CVA, and hemorrhagic CVA (P < 0.001). Patients with hemorrhagic CVA showed significantly lower serum potassium level than patients with TIA and ischemic CVA (P < 0.001). Correspondingly, it was observed that serum sodium to potassium ratio was higher in patients with TIA, ischemic CVA, and hemorrhagic CVA (P < 0.001). In patients with hemorrhagic CVA serum sodium to potassium ratio was higher when compared to patients with TIA and ischemic CVA (P < 0.001).

CONCLUSION

This study shows that higher serum sodium and lower serum potassium level may be associated with higher incidence of CVA. Further studies are paramount to elucidate the role of serum electrolyte levels in vascular events.

The importance of potassium in managing hypertension

Dietary potassium intake has been demonstrated to significantly lower blood pressure (BP) in a dose-responsive manner in both hypertensive and nonhypertensive patients in observational studies, clinical trials, and several meta-analyses. In hypertensive patients, the linear dose-response relationship is a 1.0 mm Hg reduction in systolic BP and a 0.52 mm Hg reduction in diastolic BP per 0.6 g per day increase in dietary potassium intake that is independent of baseline potassium deficiency. The average reduction in BP with 4.7 g (120 mmol) of dietary potassium per day is 8.0/4.1 mm Hg, depending race and on the relative intakes of other minerals such as sodium, magnesium, and calcium. If the dietary sodium chloride intake is high, there is a greater BP reduction with an increased intake of dietary potassium. Blacks have a greater decrease in BP than Caucasians with an equal potassium intake. Potassium-induced reduction in BP significantly lowers the incidence of stroke (cerebrovascular accident, CVA), coronary heart disease, myocardial infarction, and other cardiovascular events. However, potassium also reduces the risk of CVA independent of BP reductions. Increasing consumption of potassium to 4.7 g per day predicts lower event rates for future cardiovascular disease, with estimated decreases of 8% to 15% in CVA and 6% to 11% in myocardial infarction.

Both high and low maternal salt intake in pregnancy alter kidney development in the offspring

In humans, low glomerular numbers are related to hypertension, cardiovascular, and renal disease in adult life. The present study was designed 1) to explore whether above- or below-normal dietary salt intake during pregnancy influences nephron number and blood pressure in the offspring and 2) to identify potential mechanisms in kidney development modified by maternal sodium intake. Sprague-Dawley rats were fed low (0.07%)-, intermediate (0.51%)-, or high (3.0%)-sodium diets during pregnancy and lactation. The offspring were weaned at 4 wk and subsequently kept on a 0.51% sodium diet. The kidney structure was assessed at postnatal weeks 1 and 12 and the expression of proteins of interest at term and at week 1. Blood pressure was measured in male offspring by telemetry from postnatal month 2 to postnatal month 9. The numbers of glomeruli at weeks 1 and 12 were significantly lower and, in males, telemetrically measured mean arterial blood pressure after month 5 was higher in offspring of dams on a high- or low- compared with intermediate-sodium diet. A high-salt diet was paralleled by higher concentrations of marinobufagenin in the amniotic fluid and an increase in the expression of both sprouty-1 and glial cell-derived neutrophic factor in the offspring's kidney. The expression of FGF-10 was lower in offspring of dams on a low-sodium diet, and the expression of Pax-2 and FGF-2 was lower in offspring of dams on a high-sodium diet. Both excessively high and excessively low sodium intakes during pregnancy modify protein expression in offspring kidneys and reduce the final number of glomeruli, predisposing the risk of hypertension later in life.

Decreased 45calcium uptake in red cells of patients with essential hypertension

Decreased 45calcium uptake was observed in red cells of 20 patients with essential hypertension. Equilibration of extracellular 45calcium with intracellular calcium was not achieved within 60 min in red cells of either hypertensive patients or control subjects. By introducing the ionophore A23187, equilibrium conditions were attained for red cells of both categories of individuals. Still the discrepancy in 45calcium uptake was preserved between them. These results support the view that red cells of hypertensive patients have an altered membrane permeability to calcium, possibly reflecting also a greater exchangeable pool of cytosolic free calcium.

Sodium elimination rate and blood pressure during normal and high salt intake in subjects with and without familial predisposition to hypertension

We have assessed the elimination rate of 22Na (ER-22Na), total exchangeable sodium (NaE), blood pressure, plasma volume (PV), haematocrit, urinary noradrenaline (U-NA) and urinary 3-methoxy-4-hydroxymandelic acid (U-VMA) in normotensive men with (n = 17) and without (n = 15) familial predisposition to hypertension. All measurements were done during habitual salt intake and after four weeks of increased salt intake (ordinary intake + 12 g NaCl/daily). On ordinary salt intake, ER-22Na, NaE, blood pressure, PV, haematocrit, U-NA and U-VMA did not differ between the groups thus indicating a normal sodium turnover in both groups and a comparable activity of the sympathetic nervous system. After 10 days of high salt intake those without familial predisposition showed signs of volume expansion and decreased sympathetic activity and those with such predisposition showed insignificant changes in the same direction. After four weeks of increased salt intake, ER-22Na had increased significantly and equally in both groups, while blood pressure and NaE remained unchanged. This indicates that the predisposed individuals had a normal ability to cope with a prolonged increase in salt intake.

Diet and arterial hypertension: is the sodium ion alone important?

Hypertension is a widespread phenomenon whose ultimate cause is still unknown. Many factors contribute to this disease, and partially for this reason, hypertension responds to different treatments in different individuals. It is difficult to generalize about therapies for general populations. In particular, the role of electrolytes in hypertension varies widely across individuals. This review focuses its attention on sodium, potassium, calcium, and magnesium ions in order to investigate whether these electrolytes play a role in the pathogenesis of arterial hypertension and its treatment. Some individuals are especially sensitive to sodium, and changing their intake of dietary sodium may lead to variations in the levels of the other electrolytes. These changes in electrolyte levels can complicate treatments for arterial hypertension in some patients.

Increased sodium concentrations in drinking water increase blood pressure in neonates

BACKGROUND

In a previous study, we found that increased sodium concentrations in the drinking water led to an increase in mean arterial pressure (MAP) and systolic blood pressure (SBP) in fourth- and fifth-grade school children. Milk powder formulae have a low content of sodium, almost identical to that of breast milk. However, the final sodium concentration in the milk formula depends upon the concentration of sodium in the diluting water, which varies remarkably.

OBJECTIVE

To evaluate changes in blood pressure during the first 2 months of life in neonates receiving low-sodium mineral water (LSMW), high-sodium tap water (HSTW), or breast milk.

DESIGN

A randomized, prospective study in a teaching hospital.

METHODS

Fifty-eight Jewish term infants maintained on milk formula were randomly assigned to two groups. Group 1 consisted of 25 infants whose formula was diluted with LSMW (Eden Spring Mineral Water) having a sodium concentration of 32 mg/l (1.4 mmol/l). Group 2 contained 33 infants whose formula was diluted with HSTW having a sodium concentration of 196 mg/l (8.5 mmol/l). Fifteen breastfed babies served as the control group (group 3). Weekly weight, height, head circumference, heart rate, and systolic (SBP), diastolic (DBP) and mean (MAP) blood pressures were recorded for each infant for 8 consecutive weeks after birth. After 8 weeks, group 1 reverted to a diet similar to that of group 2. At 6 months of age (week 24), a follow-up blood pressure measurement was performed in 11, 20 and seven infants in groups 1, 2 and 3, respectively. Blood pressure was measured during sleep. Urinary sodium : creatinine ratio was determined monthly during the initial 2 months.

RESULTS

Increases in weight and height were equal in all groups. Heart rate did not differ between groups during the entire study period. From the age of 6 weeks until week 8, MAP, SBP and DBP were found to be significantly greater in the group 2 (HSTW). In parallel, the urinary sodium : creatinine ratio was significantly greater in this group. At week 24, blood pressure values in group 1 increased towards those of group 2.

CONCLUSIONS

Diluting milk formula with tap water containing a high concentration of sodium will result in the infant being fed a high-salt diet. To equilibrate with breast milk, formula should be diluted with low-salt water. Blood pressure in the neonate is increased by a high sodium intake via drinking water.

Lifestyle modifications to prevent and control hypertension. 6. Recommendations on potassium, magnesium and calcium. Canadian Hypertension Society, Canadian Coalition for High Blood Pressure Prevention and Control, Laboratory Centre for Disease Control at Health Canada, Heart and Stroke Foundation of Canada

OBJECTIVE

To provide updated, evidence-based recommendations on the consumption, through diet, and supplementation of the cations potassium, magnesium and calcium for the prevention and treatment of hypertension in otherwise healthy adults (except pregnant women).

OPTIONS

Dietary supplementation with cations has been suggested as an alternative or adjunctive therapy to antihypertensive medications. Other options include other nonpharmacologic treatments for hypertension.

OUTCOMES

The health outcomes considered were changes in blood pressure and in morbidity and mortality rates. Because of insufficient evidence, no economic outcomes were considered.

EVIDENCE

A MEDLINE search was conducted for the period 1966-1996 with the terms hypertension and potassium, magnesium and calcium. Reports of trials, meta-analyses and review articles were obtained. Other relevant evidence was obtained from the reference lists of articles identified, from the personal files of the authors and through contacts with experts. The articles were reviewed, classified according to study design, and graded according to the level of evidence.

VALUES

A high value was placed on the avoidance of cardiovascular morbidity and premature death caused by untreated hypertension.

BENEFITS, HARMS AND COSTS

The weight of the evidence from randomized controlled trials indicates that increasing intake of or supplementing the diet with potassium, magnesium or calcium is not associated with prevention of hypertension, nor is it effective in reducing high blood pressure. Potassium supplementation may be effective in reducing blood pressure in patients with hypokalemia during diuretic therapy.

RECOMMENDATIONS

For the prevention of hypertension, the following recommendations are made: (1) The daily dietary intake of potassium should be 60 mmol or more, because this level of intake has been associated with a reduced risk of stroke-related mortality. (2) For normotensive people obtaining on average 60 mmol of potassium daily through dietary intake, potassium supplementation is not recommended as a means of preventing an increase in blood pressure. (3) For normotensive people, magnesium supplementation is not recommended as a means of preventing an increase in blood pressure. (4) For normotensive people, calcium supplementation above the recommended daily intake is not recommended as a means of preventing an increase in blood pressure. For the treatment of hypertension, the following recommendations are made. (5) Potassium supplementation above the recommended daily dietary intake of 60 mmol is not recommended as a treatment for hypertension. (6) Magnesium supplementation is not recommended as a treatment for hypertension. (7) Calcium supplementation above the recommended daily dietary intake is not recommended as a treatment for hypertension.

VALIDATION

These guidelines are consistent with the results of meta-analyses and recommendations made by other organizations. They have not been clinically tested.

SPONSORS

The Canadian Hypertension Society, the Canadian Coalition for High Blood Pressure Prevention and Control, the Laboratory Centre for Disease Control at Health Canada, and the Heart and Stroke Foundation of Canada.

Nifedipine effectively lowers salt-induced high blood pressure in diabetic rats

This study examined the antihypertensive efficacy of nifedipine (a calcium channel blocker) in salt-loaded alloxan-diabetic rats. Significant increases in basal mean arterial blood pressures were observed after six weeks of high salt (8% NaCl) feeding in both diabetic (p < 0.05) and nondiabetic (p < 0.05) rats. The values were 129.95+/-3.14 mmHg for control (C); 149.22+/-8.83 mmHg for nondiabetic salt-fed (N-SF) and 150.60+/-8.01 mmHg for diabetic salt-fed (D-SF) groups. The non-salt-fed diabetic group (D) had a pressure of 136.75+/-6.66 mmHg. The maximum mean arterial blood pressures in response to noradrenaline (10(-9)-10(-5) M) infusion were significantly (p < 0.05) higher in the N-SF and D-SF groups than in the control. Nifedipine (100 microg/Kg) reduced significantly the pressures (both before and following noradrenaline infusion) in the salt-fed groups (p < 0.001). The inhibitory effect of nifedipine was more marked (p < 0.01) in the diabetic salt-fed than in the nondiabetic salt-fed. It is therefore suggested that nifedipine is effective in lowering salt-induced high blood pressure in diabetic rats.

Elemental analysis of blood of Nigerian hypertensive subjects

Proton-induced X-ray emission (PIXE) has been used to obtain the concentrations of 11 elements (P, S, Cl, K, Ca, Fe, Cu, Zn, Br, Rb, and Cd) in whole-blood samples of 16 hypertensive subjects (mean age: 52.5 +/- 0.5 yr) and 18 age-matched controls (mean age: 51.5 +/- 0.5 yr) in a Nigerian population. The results of the study indicate that the hypertensive subjects have significantly higher mean concentration of Cl, Cd, Cu, and Zn when compared with the controls, and the mean concentration of P, K, and Ca was found to be significantly lower in the hypertensive group in comparison to the controls. Furthermore, the Zn:Cd ratio was found to be significantly higher in the controls than in the hypertensives, and the Cu:Zn ratio was significantly higher in the hypertensives.

Renal function in the elderly: impact of hypertension and cardiac function

In senescence renal function is thought to decline markedly even in the absence of renal disease. It has also been proposed that the changes in renal function with age are not uniform and that confounding factors such as hypertension or atherosclerosis may play a role. We performed a comprehensive study to compare several aspects of renal function in four groups: (i) young healthy normotensive subjects (N = 24; 13 males; mean age 26 +/- 3 years); (ii) elderly healthy normotensive subjects (elderly NT; N = 29; 13 males; 68 +/- 7 years); (iii) elderly treated and untreated hypertensive patients (elderly HT; N = 25; 13 males; 70 +/- 6 years); and (iv) elderly patients with compensated mild to moderate heart failure (elderly HF; N = 14; 6 males; 69 +/- 6 years). Compared to young subjects mean GFR (C(In)) and ERPF (C(PAH)) were significantly lower in the elderly, despite similar mean plasma creatinine levels (young, 121 +/- 11, 650 +/- 85 ml/min/1.73 m2; elderly NT, 103 +/- 11, 486 +/- 102; elderly HT, 103 +/- 13, 427 +/- 55; elderly HF, 92 +/- 14, 377 +/- 103). Nevertheless, GFR was within the normal range in the majority of elderly NT and HT, but not in elderly HF. ERPF was significantly lower in elderly HT as compared with elderly NT, and still lower in elderly HF. Mean renovascular resistance and filtration fraction were significantly higher in the elderly, particularly in elderly HT and HF as compared with the young. Mean fractional excretion of Na+ was similar in all groups studied, but the lithium clearance was significantly lower in the elderly, suggesting a greater proximal and less distal sodium reabsorption in senescence. In the elderly, mean PTH concentration and urinary excretion of pyridoline cross-links were significantly higher and mean 25-(OH)D3, calcitriol and phosphate concentrations significantly lower; the correlation between PTH and GFR was significant (r = -0.432, P < 0.001). The results document that the decrease in renal hemodynamics with senescence is less marked than suggested by some studies using less stringent methodology and inclusion criteria. Comorbid conditions confound renal function in the elderly. Age-associated changes in renal hemodynamics are accompanied by significant alterations of renal hormones and of renal sodium handling.

The effect of potassium supplementation in persons with a high-normal blood pressure. Results from phase I of the Trials of Hypertension Prevention (TOHP). Trials of Hypertension Prevention (TOHP) Collaborative Research Group

We conducted a randomized, double-blind, placebo-controlled trial of oral potassium chloride supplementation (60 mmol/d) in 353 men and women with an initial average diastolic blood pressure between 80 and 89 mm Hg. In the active (n = 178) compared to the placebo (n = 175) treatment group, the urinary potassium level was significantly (p < 0.001) increased by an average of 44.0 and 42.3 mmol/24 h following 3 and 6 months of therapy, respectively. Compared to placebo, active treatment was associated with a small (mean = 1.8 mm Hg) but significant (p = 0.04) reduction in diastolic blood pressure following 3 months of therapy. Following 6 months, however, this apparent treatment effect had virtually disappeared (mean reduction in diastolic blood pressure = 0.3 mm Hg). There was no significant effect of potassium supplementation on systolic blood pressure at either follow-up visit. There was a significant, independent, dose-response relationship between change in both 24-hour urinary potassium excretion and urinary sodium-potassium ratio and the corresponding change in diastolic blood pressure (-1.49 mm Hg for the highest versus the lowest quartile of change in urinary potassium excretion.

Direct effect of insulin on 45calcium uptake in human erythrocytes

OBJECTIVE

High blood pressure is prevalent in obesity and non-insulin dependent diabetes mellitus; both conditions, with insulin resistance and essential hypertension, have been associated with increasing intra-erythrocytic levels of calcium ions. We tested the hypothesis of whether insulin itself might be responsible for the abnormal red cell cytosolic free calcium.

DESIGN

The ionic effects of insulin were studied on the kinetics of 45calcium uptake in vitro in normal human erythrocytes.

SETTING

The study was performed in the outpatient clinic of a central hospital.

SUBJECTS

Sixteen healthy, normotensive individuals with normal body mass index were recruited for the study.

MAIN OUTCOME MEASURES

Blood from eight individuals was used for time-dependent studies of 45calcium uptake in erythrocytes and blood from another eight individuals was used for dose-dependent studies of insulin effect.

RESULTS

The rate of 45calcium influx in red blood cells has two components, a fast component (0-10 min), which measures the initial rate of 45calcium influx, and a slow component (10-60 min) probably reflecting a relatively large backflux of calcium (calcium efflux), which accordingly determines an apparent low rate of 45calcium influx between 10-60 min. The uptake was linear with time between 10-120 min regardless of insulin being present or not. Insulin at a concentration of 120 mU L-1 significantly decreased the 45calcium uptake in a time-dependent fashion between 10-120 min. The uptake was 508 (+/- 59) at 60 min in the presence of insulin vs. a control value of 529 (+/- 59) pmol mL red blood cells-1 (P < 0.001). The corresponding figures at 120 min were 742 (+/- 109) and 767 (+/- 127), respectively (P = 0.02). Inconsistent results were obtained on 45calcium uptake at 60 min by varying insulin concentrations from 40-640 mU L-1 and a dual effect of insulin on 45calcium uptake could not be excluded, one at a fairly low concentration of insulin (40-120 mU L-1) and another at a high concentration (160-640 mU L-1).

CONCLUSION

The data indicate a direct role of insulin in the transport process of calcium into normal human erythrocytes.

Potassium inhibits free radical formation

We conducted this study to determine whether physiological changes in potassium concentration affect free radical formation by vascular cells. We assessed the effects of potassium on reactive oxygen species formed by cultured endothelial and monocyte/macrophage cells or freshly isolated human white blood cells by cytochrome c reduction or luminol chemiluminescence, respectively. Reducing potassium concentration of endothelial cell media (normally 5.1 to 6.1 mmol/L) to 3.0 mmol/L exponentially increased the rate of cytochrome c reduction, up to 8.4-fold at 2 hours; raising potassium concentration to 5.5 or 7.0 mmol/L at 1 hour reduced the maximal rate of cytochrome c reduction by 86% or 93%. Subsequent studies were done 30 to 75 minutes after media change. Potassium reduced the rate of cytochrome c reduction by 49% (endothelial cells) to 55% (monocytes/macrophages) between 3.0 and 7.0 mmol/L; the greatest decrement (20% to 26%) occurred between 3.0 and 4.0 mmol/L. Superoxide dismutase reduced the rate of cytochrome c reduction by 62% or 50% in endothelial or monocyte/macrophage cells. Potassium had no effect on the rate of cytochrome c reduction in the presence of superoxide dismutase. Increasing potassium concentration from 1.48 to 4.77 or 7.94 mmol/L also reduced luminol chemiluminescence in human white blood cells challenged by 1 to 10 mg/mL zymosan. We conclude that physiological increases in potassium concentration inhibit the rate of superoxide anion formation by cell lines derived from endothelium and from monocytes/macrophages and reactive oxygen species formation by human white blood cells.

Insulin resistance--not hyperinsulinemia--is pathogenic in essential hypertension

A correlation between essential hypertension and insulin resistance/hyperinsulinemia is well documented, and there is adequate reason to believe that this association is causal. The common presumption that hyperinsulinemia mediates this connection is based on studies demonstrating various pressor effects of insulin, such as sodium retention, activation of the sympathetic nervous system, and stimulation of renin output. However, a consideration of physiological parameters in essential hypertensives indicates that these insulin-mediated pressor effects are unlikely to play a crucial pathogenic role in most cases of essential hypertension. Moreover, physiological elevation of insulin following a meal is typically associated with a reduction of blood pressure in hypertensives and the elderly. Euglycemic insulin clamps tend to reduce blood pressure in elderly subjects, and prolonged maintenance of hyperinsulinemia in animals does not raise blood pressure. In fact, insulin has long been known to have direct vasodilatory or antipressor effects on resistance vessels, and there is recent evidence that insulin reduces vascular resistance in skeletal muscles to facilitate glycogen storage after a meal. I propose that essential hypertensives experience a net deficit of insulin activity in vascular muscle, and that, in conjunction with other genetic or acquired defects of electrolyte transport, this leads to an increase in basal vascular tone and a hypersensitivity to pressor agents. Correction of insulin resistance usually aids blood pressure control, and in addition may mitigate the excess cardiovascular risk associated with hypertension.

Relationship between self-monitoring of diet and exercise change and subsequent risk factor changes in children and adults

Self-monitoring is often used in health behaviour change programs; but it is not known to what extent self-monitoring data are valid and useful in predicting changes in cardiovascular disease (CVD) risk. Subjects included 72 Anglo adults, 68 Anglo children, 80 Mexican-American adults and 94 Mexican-American children. Subjects were families with fifth and sixth grade children who participated in an 18-session family-based diet and exercise change program designed to reduce CVD risk. During the intervention, each participant self-monitored diet and aerobic physical activity. Families were measured at baseline, 3, 12, and 24 months. For adults, self-monitored changes in diet correlated with changes in body mass index, systolic blood pressure, total cholesterol and LDL 1 and 2 years later. Correlations between self-monitored diet and diet-related risk factor changes were not observed among children. Correlations between self-monitored exercise and subsequent risk factor changes were not observed among adults. For children, self monitored changes in aerobic physical activity correlated significantly with changes in VO2Max and HDL/LDL ratio 1 and 2 years later. Thus, this study provides some support for the predictive validity of diet self-monitoring in adults and exercise self-monitoring in children.

Hypertension and the kidney--an overview

The kidney plays a major role in the genesis of any type of hypertension, as demonstrated by experiments which show that hypertension can be "transplanted" when the kidney itself is transplanted. Hypertension is common in patients with renal disease, and may occur even at normal glomerular filtration rates. The mechanisms that promote hypertension and are involved in renal disease comprise both activation of pressor mechanisms and failure of depressor mechanisms, the latter having been considerably less well studied. The major pressor mechanisms are an abnormal pressure-natriuresis relationship and inappropriate activity of the renin-angiotensin system.

Neuroendocrine mechanisms and cardiovascular homeostasis in the elderly

Reduced homeostatic capacity is typical of the aging process and is particularly apparent in changes in the neuroendocrine control of cardiovascular homeostasis. Not only is there reduced beta-adrenoceptor responsiveness, but reduced baroreflex function also occurs with age. These result in increased sensitivity to the therapeutic and postural hypotensive effects of diuretics and vasodilators. Increased total body sodium and reduced activity of the renin-angiotensin-aldosterone system may also contribute to the therapeutic effect of diuretics and salt restriction in elderly hypertensives. In addition, atrial natriuretic peptide levels are increased in the elderly and may in part be responsible for the suppressed renin and aldosterone levels found in older groups. Vasopressin secretion and thirst are also disturbed with age, and may act in concert with declining renal function to predispose the elderly to disturbances of water balance. An understanding of these neuroendocrine changes with age is important to maximize therapeutic benefit and to minimize adverse effects in the treatment of hypertension in the elderly.

Potassium and blood pressure

The relationships between serum potassium and urinary excretion of potassium and blood pressure were determined in an unmedicated adult population with a wide range of blood pressure (mean arterial blood pressure 100-130 mm Hg, n = 71). Inverse correlations between both serum potassium concentration and urinary excretion of potassium and standing (but not supine) mean blood pressure were seen (r = -0.41, p less than 0.005 and r = -0.33, p less than 0.01 respectively). These relationships persisted also when the influences of age, sex, obesity and kidney function were taken into account in a multiple regression analysis. The present observation is in accordance with previous reports of an association between potassium metabolism and blood pressure.

Sodium and potassium intake and blood pressure change in childhood

OBJECTIVE

To assess the association between sodium and potassium intake and the rise in blood pressure in childhood.

DESIGN

Longitudinal study of a cohort of children with annual measurements during an average follow up period of seven years.

SETTING

Epidemiological survey of the population of a suburban town in western Netherlands.

SUBJECTS

Cohort of 233 children aged 5-17 drawn at random from participants in the population survey.

MAIN OUTCOME MEASURES

At least six annual timed overnight urine samples were obtained. The mean 24 hour sodium and potassium excretion during the follow up period was estimated for each participant and the sodium to potassium ratio calculated. Individual slopes of blood pressure over time were calculated by linear regression analysis.

RESULTS

No significant association was observed between sodium excretion and the change in blood pressure over time. The mean systolic blood pressure slopes, however, were lower when potassium intake was higher (coefficient of linear regression -0.045 mm Hg/year/mmol; 95% confidence interval -0.069 to -0.020), and the change in systolic pressure was greater when the urinary sodium to potassium ratio was higher (0.356 mm Hg/year/unit; 95% confidence interval 0.069 to 0.642). In relation to potassium this was interpreted as a rise in blood pressure that was on average 1.0 mm Hg (95% confidence interval -1.65 to -0.35) lower in children in the upper part of the distribution of intake compared with those in the lower part. The mean yearly rise in systolic blood pressure for the group as a whole was 1.95 mm Hg. Urinary electrolyte excretion was not associated with diastolic blood pressure.

CONCLUSION

Dietary potassium and the dietary sodium to potassium ratio are related to the rise in blood pressure in childhood and may be important in the early pathogenesis of primary hypertension.

Effect of dietary potassium on blood pressure, renal function, muscle sympathetic nerve activity, and forearm vascular resistance and flow in normotensive and borderline hypertensive humans

We evaluated the effect of a low potassium diet on blood pressure in normotensive (NT) and in borderline hypertensive subjects (BHT). There were 11 BHT men (age, 24.6 +/- 1.2 years) and 10 NT men (age, 23.5 +/- 1.0 years). Subjects were studied while on both low potassium, high sodium (30 meq/day, 400 meq/day) diets and high potassium, high sodium (100 meq/day, 400 meq/day) diets, each taken for 6 days. During the low potassium diet, daytime ambulatory systolic blood pressure increased in both NT (123 +/- 5 mm Hg, low potassium, vs. 116 +/- 4 mm Hg, high potassium, p less than 0.01) and BHT groups (134 +/- 3, low potassium, vs. 124 +/- 3, high potassium, p less than 0.001). Mean blood pressure was not different in NT during the two diets but was significantly higher during the low potassium diet in BHT subjects (97 +/- 2 mm Hg low potassium, vs. 92 +/- 1 mm Hg, high potassium, p less than 0.05) without change in heart rate in BHT subjects during the two diets. Low potassium diet increased the postural rise in diastolic blood pressure when subjects changed from the supine position to quiet standing (standing diastolic blood pressure for NT: low potassium, 79 +/- 2 mm Hg vs. high potassium, 72 +/- 2 mm Hg; for BHT: low potassium, 89 +/- 2 mm Hg vs. high potassium diet, 83 +/- 2 mm Hg, p less than 0.01). The effects of low potassium diet on blood pressure were not related to marked changes in renal hemodynamics, in plasma renin activity, in aldosterone, or in norepinephrine, nor to increases in forearm vascular resistance or in muscle sympathetic nerve activity. In fact, muscle sympathetic nerve activity decreased in the BHT group during low potassium compared with high potassium diets (p less than 0.001) and did not change in the NT group. Sympathetic nerve activity was also higher in BHT compared with the NT group during high potassium and low potassium diets, p less than 0.001. In the NT group, the low potassium diet was associated with lower hematocrit levels, weight gain, and increased 24 hour urinary calcium levels. After the low potassium diet, serum potassium fell in both groups, and serum phosphorus fell significantly in the BHT group.(ABSTRACT TRUNCATED AT 400 WORDS)

Non-pharmacologic measures for lowering blood pressure

Nondrug measures have proven effective, to some extent, in lowering blood pressure, especially in mild hypertensives, in many well-controlled studies. The proven measures are reduction of a) salt (less than 5 g/day), b) alcohol (less than 30 ml/day) intake, and c) obesity, and d) regular physical exercise (30-60 minutes/day) and e) mental relaxation. The reported effectiveness of each of these measures ranges from one third to two thirds in mild hypertensives. Should all these nondrug measures, together with cessation of smoking, be applied in all mild hypertensives, it might help prevent their progression to moderate or even severe hypertension with complications, such as coronary heart disease in particular, thereby solving most of the problems that antihypertensive drugs have left behind.

Total body electrolyte composition in patients with heart failure: a comparison with normal subjects and patients with untreated hypertension

Total body elemental composition was measured in 40 patients with well documented heart failure who were oedema-free on digoxin and diuretics. The results were compared with values for 20 patients with untreated essential hypertension matched for height, weight, age, and sex. Total body potassium alone was also measured in 20 normal subjects also matched for anthropomorphic measurements. Patients with hypertension had a very similar total body potassium content to that of normal subjects, but patients with heart failure had significantly reduced total body potassium. This could not be explained by muscle wasting because total body nitrogen, largely present in muscle tissue, was well maintained. When total body potassium was expressed as a ratio of potassium to nitrogen mass a consistent depletion of potassium was revealed in the group with heart failure. Potassium depletion was poorly related to diuretic dose, severity of heart failure, age, or renal function. Activation of the renin-angiotensin-aldosterone system was, however, related to hypokalaemia and potassium depletion. Such patients also had significantly lower concentrations of serum sodium and blood pressure. Serum potassium was related directly to total body potassium. Despite the absence of clinically apparent oedema total body chlorine was not consistently increased in heart failure, but the calculated extracellular fluid volume remained expanded in the heart failure group. Total body sodium was significantly increased in patients with heart failure, but less than half of this increase could be accounted for by extracellular fluid volume expansion. Potassium depletion in heart failure may account in part for the high frequency of arrhythmias and sudden death in this condition.

Cations and hypertension: sodium, potassium, calcium, and magnesium

The association between sodium intake and hypertension has been studied for almost a century. More recently, it has been suggested that abnormalities in dietary intake of potassium, calcium, and magnesium may play a major role in the pathogenesis of hypertension. A critical analysis of selected data from animal and human studies is discussed.

'Sodium sensitivity' in man

Increased cell membrane permeability to sodium is proposed as the initial event leading to high blood pressure in susceptible subjects when sodium intake is increased. All cells, including circulating cells, would be affected, but a key role for endothelial cells in the pathophysiology of the diastolic blood pressure elevation is proposed. Involvement of capillary endothelium could increase capillary permeability to proteins, and thereby would contribute to the altered fluid distribution on the high sodium diet which has been observed. If movement of fluid into the interstitium raised interstitial fluid pressure, venous capacitance would fall and right atrial pressure would rise. Several mechanisms would cause vascular smooth muscle tone to increase. Altered fluid distribution correlates with the rise in diastolic blood pressure from reduced sodium to high sodium diet, but arteriolar constriction would reduce capillary flow so altered fluid distribution occurs first. Arteriolar constriction could serve as a negative feedback to the raised atrial filling pressure by reducing raised capillary flow, which would decrease both altered fluid distribution and interstitial fluid pressure rise. Consequently, diastolic blood pressure would be chronically raised in 'sodium sensitive' subjects taking increased amounts of sodium in the diet. The relationship of the findings to "essential" hypertension and to premorbid cardiovascular sequelae, and the key role of capillary endothelium in the development of "essential" hypertension is discussed.

Effects of age on renal sodium homeostasis and its relevance to sodium sensitivity

Age-related changes in blood pressure, renal function, and sodium homeostasis suggest that sodium sensitivity of blood pressure may also be influenced by age. Blood pressure was measured in 378 normal volunteers and 198 patients with essential hypertension after an intravenous infusion of normal saline and after sodium and volume depletion. Those whose mean arterial blood pressure decreased more than 10 mm Hg after sodium and volume depletion were considered sodium-sensitive, whereas those with a decrease of less than 5 mm Hg were considered sodium resistant. The normal and hypertensive subjects were divided into groups of those above and those below 40 years of age. The blood pressure responses of both older and younger groups were normally distributed, indicating that blood pressure could either decrease or increase following volume depletion. Older hypertensive and normotensive subjects are more likely to be sodium sensitive. They usually have lower renin values than do younger subjects, but substantial heterogeneity is found. Age and renin status do not reliably predict sodium sensitivity. Volume contraction and dietary sodium restriction are more likely to decrease blood pressure in older than in younger subjects, but regimens must be tailored individually.

Potassium depletion ameliorates hypertension in spontaneously hypertensive rats

The hemodynamic effect of moderate K+ depletion in hypertension is unknown. Since severe K+ depletion reduces systemic vascular resistance in normotensive rats, we determined the effect of K+ depletion on the natural history of hypertension in spontaneously hypertensive rats (SHR). Wistar-Kyoto rats (WKY) and SHR were fed a K+-replete, a moderately K+-depleted, or a severely K+-depleted diet. After 6 weeks, systemic vascular resistance was reduced by 25% in WKY on the severely K+-depleted diet while mean arterial pressure and systemic vascular resistance were comparable in WKY on the other two diets. In SHR on the severely K+-depleted diet for 6 weeks, muscle K+ was reduced by 23% and growth rate by 65%. In SHR on the moderately K+-depleted diet, growth rate was reduced by 23% after 3 weeks. By 6 weeks, however, muscle K+ was reduced by 5 to 6% and growth rate was comparable to that in SHR receiving the K+-replete diet. The administration of either K+-depleted diet prevented the development of hypertension (systolic blood pressure: severely depleted, 116 +/- 4; moderately depleted, 122 +/- 3; K+-replete, 155 +/- 5 mm Hg; p less than 0.001 compared with both K+-depleted groups) and reversed established hypertension (systolic blood pressure: severely depleted, 116 +/- 4; moderately depleted, 128 +/- 3; K+-replete, 171 +/- 5 mm Hg; p less than 0.001 compared with both K+-depleted groups). The protective effect of K+ depletion was mediated by a 40% reduction in systemic vascular resistance. These results suggest that K+ depletion has a potent antihypertensive effect in SHR.(ABSTRACT TRUNCATED AT 250 WORDS)

[Salt and blood pressure]

Current information on the relationship between sodium and blood-pressure regulation is reviewed from the point of view of epidemiological, clinical and experimental research, as well as evidence from intervention studies. Among other cations, calcium also has an influence on blood pressure. Epidemiological studies in particular are handicapped by the difficulties inherent in measuring salt intake in individuals with adequate accuracy. Despite remaining uncertainties and the need for further investigation, available data from different sources and a considerable number of studies justify the recommendation that the average daily salt intake of the population should not exceed 5 g (NaCl), corresponding to 85 meq or mmol of sodium (Na). This is a goal which should be approached gradually, paying simultaneous attention to other factors likely to be involved in the primary prevention of hypertension, especially overweight, and the maintenance of a sufficient supply of iodine and fluor for which salt is used as a vehicle in many countries.

Nutritional contributors to cardiovascular disease in the elderly

Cardiovascular disease, so common in the elderly, has become an urgent public health concern. Major contributing factors include hypertension, dyslipidemia, impaired glucose tolerance, physical indolence, and cigarette smoking. Diet plays a major role in atherogenesis by its influence in blood lipids, blood pressure, and glucose tolerance, although its impact in the elderly is speculative owing to a paucity of direct evidence. But a rationale exists. Most cardiovascular risk factors are more prevalent in the elderly than in the young adult. The rise in blood pressure and blood lipids with advancing age is not inevitable. Diet may contribute to hypertension through an excess of calories, saturated fat, cholesterol, or salt and a deficiency of potassium, calcium, and magnesium. Antiatherogenic diets low in saturated fat and cholesterol, rich in fiber, and with substitution of polyunsaturated fat and restricted calories tend to normalize serum lipids and to cause lesions to involute. Emphasis on vegetable protein and fiber-rich food has merit because they provide more fiber, polyunsaturated fatty acids, magnesium, selenium, complex carbohydrate, potassium, and copper, and less cholesterol, saturated fat, and sodium. The recommended fat-modified diets are adequate in protein, vitamins, and minerals and need not be deficient in any nutrient or economically nonfeasible. The accelerating decline in cardiovascular mortality, which has included the elderly, indicates that such disease is controllable and not inevitable, even in the elderly. The decrease has occurred concurrently with reduced consumption of saturated fat and cholesterol, increased use of vegetable oils, and improved levels of cardiovascular risk factors.

Effects of volume expansion and contraction on potassium homeostasis in normal and hypertensive humans

To investigate the role of potassium on blood pressure we measured serum potassium, urinary excretion of potassium and sodium, fractional excretion of potassium, urinary sodium:potassium ratio, plasma renin activity, aldosterone, and norepinephrine during dynamic maneuvers in normotensive and hypertensive subjects. After baseline measurements, we expanded intravascular volume with infusion of intravenous saline and then induced sodium and volume depletion by diuretic administration during a low sodium salt diet. These studies were performed in 431 normotensive and 478 hypertensive subjects enabling evaluation of the effects of age, race, and sex, as well as blood pressure, on the results. Among normotensives, we found that white subjects had significantly P less than 0.05) higher levels of serum and urine potassium, fractional potassium excretion and lower urinary sodium:potassium ratios than black subjects and that males had the same patterns of differences compared to females. Similar, but less consistent racial differences were seen among the hypertensive subjects. We also observed significant (P less than .05) correlations between urinary potassium excretion and body weight in both normal and hypertensive groups. In normal subjects, a significant correlation was observed between the urinary sodium:potassium ratio and blood pressure that was not seen in the hypertensives. The latter, however, displayed a significant (P less than .05) inverse relationship between serum potassium and blood pressure. Multiple regression analysis revealed that urinary potassium excretion was influenced by age, race, sex, body weight, blood pressure, creatinine clearance, renin, and aldosterone. These observations reveal important relationships between potassium homeostasis and blood pressure control that deserve further study.

Dietary sodium and arterial blood pressure: evidence against genetic susceptibility

Thirty five subjects with both parents in the top third of their age specific blood pressure distributions and 31 subjects with both parents in the bottom third of their blood pressure distributions restricted their intake of sodium for eight weeks while taking part in a double blind, randomised crossover trial of supplements of sodium and placebo. A comparison of two periods of four weeks at different intakes of sodium showed no differences in blood pressure in either the groups as a whole or the subgroups who complied best with the diet and tablets. In the compliant subgroups mean urinary sodium excretions were above 120 mmol(mEq) and below 50 mmol/day. The study provides evidence against the hypothesis that people with a family history of high blood pressure are more susceptible in their blood pressure response to dietary sodium.

Effect of potassium depletion on two-kidney, one-clip renovascular hypertension in the rat

There is considerable controversy about the hemodynamic effect of potassium in hypertension. To determine if K depletion could alter the control of blood pressure, studies were performed in rats with 2-kidney, 1-clip renovascular hypertension (RVH) after 3 to 6 wks of severe and moderate K depletion. After application of a 0.23 mm clip to the left renal artery, rats were placed on a K-replete (KR) (240 mEq/kg), a moderately K-depleted (KDM) (59 mEq/kg), or a severely K-depleted (KDS) (5 mEq/kg) diet. After 3 wks, mean arterial pressure (MAP) reached 154 +/- 3 in KR but only 121 +/- 2 in KDM (P less than 0.01) and 106 +/- 4 mm Hg in KDS (P less than 0.001). After 6 wks, MAP was 160 +/- 8 in KR, but only 132 +/- 5 in KDM (P less than 0.01) and 129 +/- mm Hg in KDS (P less than 0.01). Plasma K at 3 wks was 4.1 +/- .1 in KR, but only 3.5 +/- .1 in KDM (P less than 0.05) and 2.3 +/- .1 mEq/liter in KDS (P less than 0.001). This was associated with an 8% decrease in muscle K in KDM and a 16% decrease in muscle K in KDS. Although KDS animals did not grow during the 6 wks of study, KDM rats gained 60% as much weight at 3 wks, and, by 6 wks, weight gain was comparable in KDM (101 +/- 9) and KR (110 +/- 9 g) animals (P = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Monovalent and divalent cations in hypertension

The relationship of four cations (sodium, potassium, calcium, magnesium) to hypertension is reviewed. It seems reasonable to advise some reduction in sodium intake, and an initial goal of a mean intake of 120 mmole per day for men and 90-100 mmole per day for women is suggested. Some increase in potassium intake may well be justifiable but is better achieved through potassium-containing foods than by any artificial supplements. The data for calcium and magnesium are not sufficiently strong to warrant any recommendation for a change in intake at present.