Potassium intake and cardiovascular reactivity in children with risk factors for essential hypertension

Cardiovascular Responses to Conflict Stress in African American Mother-Daughter Dyads

This study evaluated the effect of family conflict interactions on cardiovascular responses of African American hypertensive and normotensive mother-daughter dyads and determined degree of mother-daughter concordance of physiologic response. Sixteen African American hypertensive mothers and 21 African American normotensive mothers and their teenage daughters discussed 2 topics, one involving no conflict and the other involving participant-identified conflict. Differences in blood pressure (BP), both systolic and diastolic, and heart rate (HR) were examined. As expected, hypertensive mothers and their daughters had higher BP levels (responsivity) than did their normotensive counterparts. For mothers, differences were due largely to group differences at baseline. For daughters, differences were due largely to group differences in body mass. BP reactivity (change) did not differ significantly between the groups. Few HR effects were observed. There was moderate BP concordance and low HR concordance. The findings suggest that conflict management and body mass may be important factors to consider among families at risk for hypertension.

Gastrointestinal and renal excretion of potassium in African-Americans and White Americans

OBJECTIVE

Several studies have confirmed the remarkable observation that cumulative urinary potassium (K(+)) excretion is less in African-Americans than White Americans even when identical amounts of potassium are provided in the diet. This study was designed to examine whether this decrease in urinary potassium could be compensatory to an increase in gastrointestinal excretion of potassium in African-Americans.

METHODS

Twenty-three young, healthy, normotensive participants of both sexes and races were placed on a fixed diet of 100 mEq per day of K(+) and 180 mEq per day of sodium (Na(+)) for 9 days. All urine and stool were collected daily and analyzed for electrolytes. Blood was obtained for determination of electrolytes, blood urea nitrogen (BUN), creatinine, glucose, insulin, renin, and aldosterone at the beginning and at the end of the study period.

RESULTS

Cumulative urinary excretion of K(+) was significantly less in African-Americans (609 ± 31 mEq) compared with White Americans (713 ± 22 mEq, P = 0.015). There was no significant racial difference, however, in the cumulative gastrointestinal excretion of K (105 ± 11 versus 95 ± 9 mEq, P = 0.28) in African-Americans versus White Americans, respectively.

CONCLUSION

The racial difference in urinary K(+) handling manifested by decreased excretion of K(+) in African-Americans cannot be attributed to an increase in net gastrointestinal excretion of this cation.

Racial differences in potassium homeostasis in response to differences in dietary sodium in girls

BACKGROUND

Racial differences in the renal disposition of potassium may be related to mechanisms for the greater susceptibility to hypertension in blacks than in whites.

OBJECTIVE

Our objective was to study the racial differences in the renin-angiotensin-aldosterone system and in potassium balance in black and white girls consuming a controlled diet that was low in potassium with 2 amounts of sodium intake (low compared with high).

DESIGN

The studies reported here were performed in 40 black and 28 white girls, aged 11-15 y, under highly controlled metabolic conditions. The studies comprised 2 sessions of 20-d metabolic balance sessions, at 2 amounts of dietary sodium intake (58 and 170 mmol . L(-1) . d(-1)), in a crossover design and with a constant dietary potassium intake of 50 mmol . L(-1) . d(-1). Repeated-measures analysis of variance was used to test for racial differences in potassium output and retention by sodium intakes.

RESULTS

Thirty black and 20 white girls completed the study. Urinary potassium excretion was lower in blacks than in whites, regardless of sodium intake (P < 0.05), with no differences in fecal or sweat potassium excretion. Cumulative potassium retention was significantly higher in blacks while consuming the low sodium diet. Plasma aldosterone concentrations after upright posture were significantly lower in blacks than in whites but were similar when supine, as were urinary aldosterone excretion rates. On week 3, blood pressure, body weight, urinary volume, creatinine, and serum sodium and potassium were similar.

CONCLUSION

The well-known racial difference in urinary potassium excretion appears to be at least in part due to greater renal retention of potassium in black girls.

Screening for chronic kidney disease complications in US adults: racial implications of a single GFR threshold

BACKGROUND AND OBJECTIVES

An ideal and effective screening tool should perform equally across ethnic groups. The objective of this study was to determine whether the widely advocated creatinine-based estimated GFR (eGFR) threshold of 60 ml/min per 1.73 m(2) identifies the typical metabolic abnormalities related to chronic kidney disease equally well in minority and nonminority adults.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This objective was addressed using data for 8918 minority and nonminority adult participants in the National Health and Nutrition Examination Survey 2003 through 2006, which used stratified, multistage, probability sampling methods to assemble a nationwide probability sample of the noninstitutionalized population of the United States. Metabolic abnormalities including BP, potassium, hemoglobin, bicarbonate, uric acid, calcium, phosphorus, and parathyroid hormone were defined by fifth or 95th percentile values.

RESULTS

Among participants with eGFR <60 ml/min per 1.73 m(2), black individuals were more likely than white individuals to have low hemoglobin (adjusted odds ratio [aOR] 3.76; 95% confidence interval [CI] 1.94 to 7.28), elevated uric acid (aOR 2.15; 95% CI 1.26 to 3.68), and elevated parathyroid hormone (aOR 3.93; 95% CI 2.33 to 6.66).

CONCLUSIONS

Metabolic consequences of reduced eGFR are more common in black individuals and seem to be present at levels well above 60 ml/min per 1.73 m(2); thus, black individuals should be screened for the metabolic complications of chronic kidney at higher GFR levels.

NHANES III: influence of race on GFR thresholds and detection of metabolic abnormalities

Whether the creatinine-based glomerular filtration rate (GFR) thresholds used to define chronic kidney disease (CKD) identify metabolic abnormalities similarly in minority and nonminority populations is unknown. We addressed this question among adult participants in the Third National Health and Nutrition Examination Survey (NHANES III) (n = 15,837). GFR was estimated from serum creatinine values and metabolic abnormalities were defined by 5th or 95th percentile values. After adjustment for age, demographic characteristics, and GFR, black participants were significantly more likely than white participants to have abnormal levels of systolic and diastolic blood pressure, hemoglobin, phosphorus, and uric acid. Hispanic subjects were significantly more likely to have abnormal levels of systolic blood pressure, hemoglobin, bicarbonate, and phosphorus. Among participants with GFR < 60 mL/min per 1.73 m(2), black participants were significantly more likely to have abnormal levels of systolic and diastolic blood pressure, hemoglobin, and uric acid; Hispanic subjects were significantly more likely to have abnormal systolic blood pressure levels. Metabolic abnormalities were more common in minority populations, and low GFR appeared to have a multiplicative effect. Defining CKD using a single GFR threshold may be disadvantageous for minority populations because metabolic abnormalities are present at higher levels of GFR.

Racial differences in potassium disposal

BACKGROUND

African Americans appear relatively potassium (K(+))-deficient compared with Caucasian Americans whether on unregulated diets or on diets controlled for K(+) content.

METHODS

To determine whether extrarenal K(+) disposal was affected by race, KCl (0.5 mEq/kg in 0.9% saline) was infused over 48 minutes to 12 African American and 12 Caucasian American normotensive, healthy subjects. Identical infusions were administered before and after 10 days of fixed electrolyte intake. In addition to serum K(+), glucose, insulin, renin, and aldosterone were measured in blood, and K(+) and sodium (Na(+)) in urine voided spontaneously during the infusions. Data were analyzed using a two-factor analysis of variance (ANOVA) with repeated measures.

RESULTS

Basal serum K(+) did not differ between races (African American 3.97 +/- 0.06 mEq/L and Caucasian American 3.98 +/- 0.05, P= NS). The rise in serum K(+) during the infusion and the area under the curve of serum K(+) over the 3.5 hours of observation were both greater in African American (African American +0.82 +/- 0.07 mEq/L and Caucasian American +0.61 +/- 0.06, P= 0.001; and African American 6.9 +/- 0.5 units and Caucasian American 5.1 +/- 0.6, P= 0.0012). The 10-day period of controlled intake did not abolish these differences. Aldosterone at baseline was lower and insulin was higher in African Americans at the end of the infusion. Urinary K(+), plasma glucose, and renin levels did not differ between African Americans and Caucasian Americans.

CONCLUSION

Disposal of an intravenous (iv) K(+) load is decreased in African Americans compared with Caucasian Americans, which may reflect decreased Na(+),K(+)-ATPase activity in African Americans in vivo.

Potassium in hypertension

Potassium is the most important ion in the living cell, affecting almost every cellular function. Numerous clinical and epidemiologic studies support the knowledge that potassium is a fundamental factor in blood pressure regulation. The role of potassium in blood pressure regulation is reviewed in this article, focusing on its impact on the vascular vessel and the kidney, which are tissues strongly affected by potassium balance. The role of potassium on nitric oxide synthesis and superoxide formation is analyzed. Finally, the study of cell potassium as a marker for hypertension is discussed.

Isolated systolic hypertension, obesity, and hyperkinetic hemodynamic states in children

OBJECTIVE

To determine the factors that contribute to the pathogenesis of isolated systolic hypertension in children.

METHODS

School-based measurement was performed of blood pressure (BP), heart rate, weight, and height in 2460 students (49% Hispanic, 31% black, 13% white) 12 to 16 years of age in 8 urban public schools. An independent group of 71 untreated children underwent 24-hour ambulatory BP monitoring (ABPM) to confirm clinic hypertension and assess circadian BP patterns.

RESULTS

Hypertension and obesity were found in 17% and 23% of students, respectively. Among hypertensive students, 88% (363/413) had isolated systolic hypertension. Hypertension was more prevalent in obese than nonobese students (33% vs 11%, P <.0001). Obese hypertensive students had higher resting heart rate than nonobese normotensive patients (85.9 vs 79.6 beats/min, P <.001). Among patients who underwent ABPM, isolated systolic hypertension was found in 51% (36/71) by clinic BP and in 62% (18/29) with confirmed hypertension by ABPM. Blood pressure variability during daytime and sleep periods was higher in obese than nonobese patients for systolic BP (P <.01) and diastolic BP (P <.05).

CONCLUSIONS

The findings of increased heart rate and BP variability in obese children with isolated systolic hypertension suggest that sympathetic nervous system hyperactivity may contribute to its pathogenesis.

Normotensive salt sensitivity: effects of race and dietary potassium

-Normotensive salt sensitivity, a putative precursor of hypertension, might be quite frequent in African Americans (blacks) and less frequent in Caucasian Americans (whites), but only when dietary potassium is deficient and not when maintained well within the normal range. We tested this hypothesis in 41 metabolically controlled studies of 38 healthy normotensive men (24 blacks, 14 whites) who ate a basal diet low in sodium (15 mmol/d) and marginally deficient in potassium (30 mmol/d) for 6 weeks. Throughout the last 4 weeks, NaCl was loaded (250 mmol/d); throughout the last 3, potassium was supplemented (as potassium bicarbonate) to either mid- or high-normal levels, 70 and 120 mmol/d. Salt sensitivity, defined as an increase in mean arterial blood pressure >/=3 mm Hg with salt loading, was deemed "moderate" if increasing Collapse

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MESH Headings

• Adult
• Aged
• Bicarbonates/administration & dosage
• Black People
• Blood Pressure
• Data Interpretation, Statistical
• Humans
• Hypertension/etiology
• Hypertension/prevention & control
• Linear Models
• Male
• Middle Aged
• Potassium Compounds/administration & dosage
• Potassium Deficiency/complications
• Potassium, Dietary/administration & dosage
• Racial Groups
• Sodium Chloride, Dietary/administration & dosage
• Sodium Chloride, Dietary/adverse effects
• White People
• Black or African American

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Grants

• HL-47943 NHLBI NIH HHS
• M01-00079 PHS HHS

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Affiliation(s)

R C Morris Department of Medicine, General Clinical Research Center, University of California, San Francisco 94143-0126, USA.
A Sebastian
A Forman
M Tanaka
O Schmidlin

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