An epidemiological study of potassium status, hypertension and diabetes in Barbados

The relationships between hypertension, diabetes, potassium status and other factors were examined in a population-based sample of 464 Barbadians. A stratified random sample by gender and age (40-79 years) was obtained from enumeration registers and investigated over a three month period. The previously reported low potassium range for Barbadians was confirmed (2.9-4.7 mmol/l). Within-subject correlation of plasma potassium and 24-hour urine potassium was demonstrated by repeat investigation in 70 subjects one year later. A high prevalence of obesity, hypertension and diabetes was confirmed in this population with relatively good health care. The prevalence of hypertension (by history) was 36 percent in the whole sample. Twenty-six percent of subjects were receiving antihypertensives, yet a diastolic BP of >90 mmHg was found in 17 percent of the whole sample. Six percent of subjects had a fasting plasma glucose greater than that cited by WHO. Subjects not on thiazides, compared to those on thiazides did not show a significant difference in fasting glucose or potassium values, but did show higher uric acid and cholesterol values. Dietary analyses confirmed the traditional high starch, low fruit Barbadian diet. The major risk factors for hypertension were female gender, obesity in females and positive family history. In this study a high prevalence of hypokalemia and moderately low dietary potassium has been demonstrated, but neither potassium deficiency nor thiazide use appeared to be definitely linked to diabetes or hypertension.

Reduction in vitro of red cell glutathione reproduces defects of cellular sodium transport seen in oedematous malnutrition

Red cells in oedematous malnutrition (kwashiorkor) have an increased sodium content, 'leakiness' to sodium and enhanced sodium pumping. In non-oedematous malnutrition (marasmus) there is a reduction in the sodium pump activity. The explanation has hitherto been unknown but the glutathione content of red cells is low in kwashiorkor and normal in marasmus. We artifically lowered the glutathione content of normal red cells to values characteristic of mild oedematous malnutrition, using the enzyme inhibitors bischloronitrosourea (BCNU) and buthionine sulfoximine (BSOX). After preincubation, the cells were washed to remove the inhibitors and oxidized glutathione. Cellular content of sodium and potassium, and 86Rb influx were then measured. The reduction in glutathione reproduce the abnormalities of sodium content and flux observed in kwashiorkor. We suggest that oxidant stress in kwashiorkor, by reducing cellular glutathione, may affect cell membrane electrolyte transport. This may act through alterations in membrane sulfhydryl groups. Glutathione depletion may therefore play an important role in the clinical picture and natural history of oedematous malnutrition and may have relevance to other conditions where oxidant stress occurs. (AU)

Relationship between leucocyte sodium content and high blood pressure during development and resolution of pre-eclampsia

One hundred and five primigravidae were followed sequentially at 4-weekly intervals starting at gestational week 31. They were seen again at 6 weeks post partum. At each visit measurement were made of blood pressure as well as of leucocyte and erythrocyte sodium and potassium content. Eighty-five subjects completed the study. Seven developed pre-eclampsia. In both controls and patients who developed pre-eclampsia, leucocyte and erythrocyte sodium content increased with gestational age and fell post partum. These changes were of greater magnitude in the patients with pre-eclampsia. Cell potassium fell in both groups, but to a greater extent in patients with pre-eclampsia. These changes in cell sodium paralleled those in blood pressure in both groups. These data suggest that the excessive blood pressure changes in pre-eclampsia might be related to similar changes in cell sodium content (AU)

Slavery, salt and survival: a hypothesis on the greater prevalence of high blood pressure in Western Hemisphere blacks

High blood pressure of unknown cause (essential hypertension) is the major chronic illness contributing to premature morbidity and mortality in western hemisphere Blacks. As a group, blacks in the western hemisphere have higher mean blood pressure levels than blacks from Sub-Sahara Africa where essential hypertension is strickingly less common. Because of the similar heritage of these populations it has been suggested that blood pressure differences between them is most likely due to environmental differences such as variations in diet or biobehavioral stress. We suggest a new hypothesis: selective survival related to sodium (Na+) metabolism during the slavery period of Western hemisphere blacks and Sub-Sahara African Blacks which now play a major role in these geographic variations in blood pressure. Most blacks in the western hemisphere are descendants from a population of sub-Saharan Africans that survived the selection pressure of the trans-Atlantic slave trade and new world slavery; ancestors of most current Black Africans had no such experience. The present atricle reviews the importance of Na+ metabolism in the causes of mortality during the slave trade and estimates Na+ losses due to sweating, diarrhea and vomiting. The magnitude of these potential losses make it likely that fatal Na+ depletion was a major contributor to the high mortality. Thus, we suggest that the slave trade imposed severe demands on Na+ homepstasis and those most likely to survive were most capable of conserving Na+ than those who did not. In today's high dietary Na+ enviroment the descendants of African slaves may be more susceptible to Na+ sensitive" hypertension than the descendents of Black Africans without this heritage. (AU)

Intracellular sodium and potassium and their relationship to blood pressure and body size

In the present study twenty-seven hypertensive patients, thirty-five normotensives without familial hypertension and twelve normotensives with familial hypertension were studied cross-sectoinally with regard to their age, sex, body mass index and - most important of all - the electrolyte (sodium and potassium) composition of their red and white blood cells. The major aim of this study was to find out if there were differences between the above mentioned subject groups regarding the electrolyte composition (sodium and potassium) of their blood cells. Another aim of this study was to characterize, through multiple regression analysis, the relationship between blood pressure, body mass index, and cell sodium and potasssium. Higher RBC-Na and WBC-Na were observed in essential hypertensives and normotensives with familial hypertension versus normotensive controls without familial hypertension. Normotensives with familial hypertension had WBC-Na and RBC-Na that were not significantly different from those in essential hypertensives. RBC-K was not significantly different between normotensives with familial hypertension, normotensives without familial hypertension and essential hypertensives. WBC-K was not significantly different between normotensives with familial hypertension and essential hypertensives. Normotensives with familial hypertension had significantly higher WBC-K than normotensives without familial hypertension and essential hypertensives. Correlations that were significant in the combined normotensive-hypertensive group include: (i) The direct relationship between blood pressure (systolic, diastolic and mean) and RBC-Na and also WBC-Na. (ii) The inverse relationship between blood pressure (diastolic and mean) and RBC-K and WBC-K. (iii) The direct relationship between body mass index and WBC-Na and WBC-K. Correlations that were significant in the essential hypertensive group include: (i) The inverse relationship between blood pressure (diastolic and mean) and RBC-K and also WBC-K. (ii) The direct relationship between body mass index and WBC-Na. Most of these results are compatible with the hypothesis that sodium is involved in the pathogenesis of essential hypertension (AU)

Changes in red cell sodium content and blood pressure levels with potassium supplementation in black hypertensive patients

Red cell sodium and potassium content were measured in 24 black hypertensive patients while they were hypokalaemic on thiazide diuretic therapy and again after potassium supplements (48 meq elemental K+/day). Mean and diastolic blood pressure levels fell by 4.1-4.4 and 4.5-5.2 mm Hg respectively with potassium supplementation, while both urinary excretion of potassium and serum potassium rose. Urinary sodium excretion was unchanged. Red cell potasssium remained within the normal range but red cell sodium, initially high, fell with potassium therapy. This study confirms the importance of potassium supplementation where hypokalaemic results from diuretic therapy (AU)

Leucocyte and erythrocyte sodium and potassium levels in pregnancy: prediction of pre-eclampsia

The pathogenesis of the hypertension in pre-eclampsia, although obscure, has been related by many authorities to excessive retention. However, there are very few documented records of measurements of intracellular ionic levels and there is no concensus as to whether the levels are indeed elevated. In this thesis, a study of the leucocyte and erythrocyte sodium and potassium contents and blood pressures of two groups of pre-eclamptic primigravidae is presented. In both controls and patients who had or developed pre-eclampsia, leucocyte or erythrocyte sodium content increased with gestational age, peaking just before term and falling post partum. The potassium levels displayed the opposite pattern. These changes were of greater magnitude in patients with pre-eclampsia and were more pronounced in the leucocytes. The changes in blood pressure mirrored those in leucocyte sodium in both pre-eclamptics and controls. These data suggest that the excessive blood pressure changes in pre-eclampsia might be related to the changes in cell ionic content (AU)

Plasma arginine vasopressin response to water load during labor

To find out whether plasma vasopressin (PAVP) response to a water load during pregnancy is inappropriately high, as had been speculated, we measured PAVP by radio-immunoassay in 30 women at the time of delivery. Ten women had received infusion of aqueous glucose solution during labor for hydration (GW group); another ten received infusion of glucose solution as a vehicle for oxytocin (OT group), and ten women did not receive any intrapartum intravenous fluid therapy (controls). Serum sodium and osmolality were also determined in all the subjects. PAVP levels were significanty lower in GW (0.70) ñ 0.4 pg/ml)and OT groups (0.7 ñ 0.6 pg/ml) (P< 0.05). Significant negative correlation was seen between the amount of glucose solution infused and levels of PAVP (r = 0.61; P< 0.01). These findings suggest that during labor, the physiological relationship between serum osmolality and PAVP is intact, and that infusion of a water load in the form of aqueous glucose solution is attended by an expected lowering of PAVP. We infer that inappropriate ADH response is not the cause of water retention and hyponatremia often seen in women receiving aqueous glucose solution during labor.(AU)

Red cell sodium metabolism in human hypertension - abstract

A derangement in cell sodium homeostasis has been reputed to be the cause of primary hypertension in man. This hypothesis is supported by findings of raised intracellular sodium and suppressed sodium pump activity. These findings, however, are not universal. These experiments were designed to measure red cell sodium and potassium content and sodium transport activity as well as to define the role of plasma in these transport activities. Twelve hypertensives and 27 normotensive controls were subjected to venipuncture. Red cells were separated from plasma and the cellular content of sodium and potassium was measured. Na efflux from loaded cells was used to measure sodium pump activity and contransport. Red cell sodium content was slightly higher in hypertensive patients (10.4ñ2.8 vs 8.7ñ2.1 mMOl/l RBC, p<.05). Red cell potassium was the same in both groups (110ñ7 vs 113ñ8 mMOl/l RBC). Ouabain-sensitive sodium efflux, a measure of sodium pump activity, was the same in hypertensives and normotensives (6.69ñ2.57 vs 6.57ñ2.34 mMol/l /RBC/h). Plasma incubation produced an across-the-board reduction in sodium transport activities. Ouabain-sensitive efflux was 5.79ñ3.05 vs 4.23ñ2.66, and contransport, 0.57ñ0.28 vs 0.63ñ0.27 mMol/l RBC/h in hypertensives and normotensives respectively. We conclude that red cell sodium homeostasis is virtually identical in hypertensives and normotensives and that a circulating inhibitor is present to the same degree in both their plasmas. These data do not support the hypothesis that essential hypertension is causally associated with derangements of cell sodium metabolism (AU)

Intrapartum infusion of aquenous glucose solution, transplacental hyponatraemia and risk of neonatal jaundice

Cord serum sodium levels in three groups of 278 singleton infants, born vaginally at term, were correlated with the incidence of jaundice (serum bilirubin o85æmol/1) in the first 3 days of life. Of the 278 infants, 87 were born to mothers who were given infusions of 5 percent or 10 percent glucose in water during labour (group I), 90 were born to mothers who received glucose solution as a vehicle for oxytocin (group II), and 101 to mothers who did not receive any intravenous fluid therapy (control group). Jaundice was seen significantly more frequently in groups I (28/87, 32 percent) and II infants (30/90, 33 percent) than in the control group (12/101, 12 percent) (P<0.01), but when analysed in relation to cord serum sodium levels, the prevalence of jaundice in the normonatraemic infants (serum sodium o131 mmol/1) was similar in the three groups. On the other hand, in groups I and II jaundice occurred about 3.5 times more frequently in the hyponatraemic infants (group I (17/32, 53 percent) and II (20/39, 51 percent) than in the normonatraemic infants (P<0.01). The difference was not associated with any other perinatal or neonatal characteristic.(AU)

Sodium, potassium, and rate constants for sodium efflux in leucocytes from hypertensive Jamaicans

Leucocyte sodium and potassium content and concentrations were measured along with ouabain-sensitive and ouabain-insensitive rate constants for sodium efflux in 14 controls and 20 black patients with essential hypertension. Leucocyte sodium content was significantly increased in the patients (mean 101.1 ñ 7.8 mmol/kg dry solids v 74.5 ñ 7.6 mmol/kg dry solids; p<0.05), whereas the rate constants for sodium efflux were not significantly reduced. There was no difference between the two groups in cell potassium values. The increase in leucocyte sodium content in the presence of normal rate constants for sodium efflux suggests an increase in membrane permeability to sodium, which might be important in the pathogenesis of essential hypertension. (AU)

Leucocyte electrolytes and sodium efflux rate constants in the hypertension of pre-eclampsia

Leucocyte electrolytes were measured in pre-eclampsia and comparison was made with leucocytes from normal primigravidae and from the origional pre-eclamptic subjects 6 months after delivery when blood, pressures returned to normal. In pre-eclamptic subjects, leucocyte sodium was elevated and potassium depressed, and the rate constant for sodium efflux was depressed. These changes returned to normal after delivery. An increase in cellular sodium as a result of altered sodium pump activity may be the cause of hypertension in pre-eclampsia. (AU)

Salt wasting in severe tetanus

A 42-year-old man with severe tetanus exhibited two episodes of salt wasting. It was not possible to demonstrate either chronic renal failure or adrenal disease, conditions known to be associated with salt wasting. Studies done in this patient suggested a limitation in maximum tubular reabsorptive rate for sodium. Treatment was purely supportive (AU)

The bioavailability of potassium in bananas

Bananas are known to have a high K+ content. The bioavailability of the K+ in bananas was compared with that in Slow-K tablets in 5 normal subjects. 24-hr urinary K+ excretion was assumed to be an index of K+ absorbed from the gatro-intestinal tract. The results indicate that the K+ in bananasis available, since 24-hr K+ excretion rose significantly during the period of banana consumption. The rise in K+ excretion while taking Slow-K was however, greater, the difference between the two being highly significant (p<0.01). The possible reasons for this difference are discussed. It is suggested that bananas may be a useful and safer alternative to Slow-K for K+ supplementation in patients in whom the extra calories are not contraindicated (AU)

Leucocyte sodium, potassium and rate constants for sodium efflux in hypertension

There is a need for data on cellular electrolytes and sodium pump activity in many models of hypertension because it has become evident that if sodium is involved in hypertension, it is at the cellular level that it is important. This study was designed to measure leucocyte sodium, potassium, and rate constants for sodium efflux, total and ouabain insensitive, in animal and human hypertension. In Goldblatt-2-kidney hypertension, leucocyte electrolytes and rate constants were undisturbed. In Goldblatt-1-kidney hypertension, leucocyte, sodium content unchanged, potassium concentration was depressed, and the rate constant for total sodium efflux was lower. The passive efflux represented by the ouabain insensitive efflux, remained the same. In Goldblatt-1-kidney rats drinking 1 percent saline leucocyte sodium content fell while rate constant for total sodium efflux was increased. Ouabain insensitive efflux was unchanged. In DOCA hypertension, leucocyte sodium content was marginally elevated while the rate constant for total sodium efflux was also increased. Passive efflux was unchanged. Leucocytes from patients with essential hypertension had a high sodium content and concentration, and normal potassium content. Potassium concentration was depressed because of a higher cell water. Total sodium efflux rate constant was unchanged as was ouabain insensitive efflux. In pre-eclampsia, leucocyte sodium content and concentration were elevated while potassium content and concentration were depressed. The rate constant for total sodium efflux was lower while ouabain insensitive efflux was the same. These abnormalities disappeared six months after delivery. These findings are consistent with a hypothesis that cellular sodium is important in the pathogenesis of hypertension, but that there are at least two schemata for its involvement in the various models. (AU)