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Clinical and Experimental Hypertension... Jul 1996We examined the effect of high potassium (K) diet on oxidative stress to endothelium in hypertensive rats. Five-week-old stroke-prone spontaneously hypertensive rats...
We examined the effect of high potassium (K) diet on oxidative stress to endothelium in hypertensive rats. Five-week-old stroke-prone spontaneously hypertensive rats (SHRsp) were fed a 5% high NaCl diet containing either 0.5% normal K (n = 28) or 2.1% high K (n = 19) for 6 weeks, and lipid peroxides in the aortic intima and plasma were measured. Lipid peroxides were extracted into an organic solvent to avoid the interference of carbohydrates or glycoproteins, and malondialdehyde (MDA) produced from lipid peroxides by acid-heating was measured by its reaction to thiobarbituric acid. The antioxidant butylated hydroxytoluene prevented spurious lipid peroxide formation during the whole procedure, and optimum Fe3+ allowed a maximum MDA production from lipid peroxides. The high K SHRsp showed lower lipid peroxide levels than the normal K SHRsp both in the intima (5.6 +/- 0.3 vs. 7.2 +/- 0.4 nmol MDA/mg fatty acids, p < 0.003) and plasma (0.91 +/- 0.08 vs. 1.46 +/- 0.10 nmol MDA/ml, p < 0.001). Mean arterial pressure was slightly lower by 13 mmHg in the high K SHRsp, but these differences were still obvious even when we compared groups of rats with precisely matching blood pressures. These results indicate that high K diets reduce oxidative stress on the endothelium of high NaCl-fed SHRsp independently of blood pressure changes. This effect may be involved in the mechanism by which high K diets protect endothelium and reduce stroke incidence in hypertensive animals. Thus, we improved the method of lipid peroxide measurement and propose the protective effects of high K diet against oxidative stress to endothelium in hypertension animals.
Topics: Animals; Antioxidants; Blood Vessels; Butylated Hydroxytoluene; Cerebrovascular Disorders; Endothelium, Vascular; Ferric Compounds; Genetic Predisposition to Disease; Hypertension; Lipid Peroxides; Male; Malondialdehyde; Oxidative Stress; Potassium, Dietary; Rats; Rats, Inbred SHR; Rats, Inbred WKY; Thiobarbiturates; Tunica Intima
PubMed: 8781752
DOI: 10.3109/10641969609081773 -
Revista Medica de Chile Nov 1997Sodium and potassium ions are involved in the regulation of blood pressure and the genesis of hypertension. (Comparative Study)
Comparative Study
BACKGROUND
Sodium and potassium ions are involved in the regulation of blood pressure and the genesis of hypertension.
AIM
To assess internal potassium balance, as a measure of sodium pump activity, in subjects with essential hypertension and diabetic patients.
PATIENTS AND METHODS
Eleven hypertensive subjects, 5 non-insulin-dependent diabetics and 16 age matched controls were studied. An acute oral load of 0.8 mEq/Kg body weight of KCl was administered and blood samples were drawn every 30 min thereafter, until 120 min, to measure plasma K+ levels. Urinary K+ excretion during this period was also measured. In eight hypertensive patients, the test was repeated after two week of supplementation with 60 mEq/day of KCl. The maximal increase in plasma potassium levels and the time required to achieve the maximum concentration was recorded.
RESULTS
All patients had normal serum creatinine levels. Mean fasting blood glucose of diabetic patients was 133 +/- 15.1 mg/dl. No difference between patients and controls in maximal increase plasma potassium increase, was observed. In hypertensive patients the lapse to achieve the maximal potassium concentration was longer than in controls. After the period of potassium supplementation in hypertensive patients, there was a significant increase in basal plasma K+ levels and the temporal pattern of plasma potassium increase was similar to that of controls. Between 63 and 68% of retained K+ load was translocated to the intracellular space at 120 min in all study groups.
CONCLUSIONS
Internal potassium balance is not significantly altered in subjects with essential hypertension or in non-insulin-dependent diabetics.
Topics: Adult; Aged; Diabetes Mellitus, Type 2; Humans; Hypertension; Middle Aged; Potassium; Potassium Chloride; Potassium, Dietary
PubMed: 9609049
DOI: No ID Found -
The Journal of Nutrition Sep 1993
Review
Topics: Animals; Bone Density; Bone and Bones; Caffeine; Calcium; Calcium, Dietary; Humans; Phosphates; Potassium, Dietary; Rats; Sodium, Dietary
PubMed: 8360788
DOI: 10.1093/jn/123.9.1609 -
Journal of Applied Physiology Nov 1955
Topics: Anions; Calcium; Calcium, Dietary; Ions; Magnesium; Potassium; Sodium; Sodium, Dietary; Taste; Taste Threshold; Water; Water Supply
PubMed: 13271255
DOI: 10.1152/jappl.1955.8.3.283 -
Kidney International Oct 1998Potassium depletion increases HCO3- reabsorption in outer medullary collecting duct (OMCD) by activation of colonic (c) H-K-ATPase (HKA). The purpose of the current...
BACKGROUND
Potassium depletion increases HCO3- reabsorption in outer medullary collecting duct (OMCD) by activation of colonic (c) H-K-ATPase (HKA). The purpose of the current experiments was to examine the role of the isoforms of HKA in HCO3- reabsorption by terminal inner medullary collecting duct (IMCD) cells in potassium depletion.
METHODS
Sprague-Dawley rats were fed a potassium-free diet and studied after 8 to 10 days. mRNA expression of HKA isoforms in terminal portion of inner medulla was examined and correlated with HCO3- reabsorption in the terminal IMCD.
RESULTS
Gastric (g) HKA mRNA decreased whereas colonic (c) HKA mRNA expression was heavily induced in terminal portion of inner medulla in potassium depleted rats. Net HCO3- flux (JtCO2) in terminal IMCD increased in potassium depletion (4.56 to 7.06 pmol/min/mm tubule length, P < 0.001). In normal rats, 1 mM ouabain in perfusate had no effect on JtCO2, whereas 10 microM Schering 28080 (SCH) decreased JtCO2 to 2.4 (P < 0.002). In KD rats, 1 mM ouabain decreased JtCO2 to 4.9 (P < 0.005) and 10 microM SCH decreased JtCO2 to 3.3 (P < 0.001). However, the inhibitory effects of SCH and ouabain on JtCO2 in potassium depleted animals were not additive.
CONCLUSIONS
The data indicate that gHKA is suppressed whereas cHKA is induced in potassium depletion and mediates increased HCO3- reabsorption in terminal IMCD. The results further indicate that cHKA in vivo is sensitive to both SCH and ouabain.
Topics: Animals; Bicarbonates; Colon; Enzyme Induction; H(+)-K(+)-Exchanging ATPase; Hypokalemia; Imidazoles; In Vitro Techniques; Ion Transport; Isoenzymes; Kidney Medulla; Kidney Tubules, Collecting; Male; Ouabain; Perfusion; Potassium; Potassium, Dietary; RNA, Messenger; Rats; Rats, Sprague-Dawley; Stomach
PubMed: 9767539
DOI: 10.1046/j.1523-1755.1998.00105.x -
American Journal of Physiology. Renal... Jul 2000Intercalated cells (ICs) from kidney collecting ducts contain proton-transporting ATPases (H(+)-ATPases) whose plasma membrane expression is regulated under a variety of...
Intercalated cells (ICs) from kidney collecting ducts contain proton-transporting ATPases (H(+)-ATPases) whose plasma membrane expression is regulated under a variety of conditions. It has been shown that net proton secretion occurs in the distal nephron from chronically K(+)-depleted rats and that upregulation of tubular H(+)- ATPase is involved in this process. However, regulation of this protein at the level of individual cells has not so far been examined. In the present study, H(+)-ATPase activity was determined in individually identified ICs from control and chronically K(+)-depleted rats (9-14 days on a low-K(+) diet) by monitoring K(+)- and Na(+)-independent H(+) extrusion rates after an acute acid load. Split-open rat cortical collecting tubules were loaded with the intracellular pH (pH(i)) indicator 2', 7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein, and pH(i) was determined by using ratiometric fluorescence imaging. The rate of pH(i) recovery in ICs in response to an acute acid load, a measure of plasma membrane H(+)-ATPase activity, was increased after K(+) depletion to almost three times that of controls. Furthermore, the lag time before the start of pH(i) recovery after the cells were maximally acidified fell from 93.5 +/- 13.7 s in controls to 24.5 +/- 2.1 s in K(+)-depleted rats. In all ICs tested, Na(+)- and K(+)-independent pH(i) recovery was abolished in the presence of bafilomycin (100 nM), an inhibitor of the H(+)-ATPase. Analysis of the cell-to-cell variability in the rate of pH(i) recovery reveals a change in the distribution of membrane-bound proton pumps in the IC population of cortical collecting duct from K(+)-depleted rats. Immunocytochemical analysis of collecting ducts from control and K(+)-depleted rats showed that K(+)-depletion increased the number of ICs with tight apical H(+)ATPase staining and decreased the number of cells with diffuse or basolateral H(+)-ATPase staining. Taken together, these data indicate that chronic K(+) depletion induces a marked increase in plasma membrane H(+)ATPase activity in individual ICs.
Topics: Acid-Base Equilibrium; Ammonium Chloride; Animals; Anti-Bacterial Agents; Electrolytes; Female; Fluoresceins; Fluorescent Dyes; Hydrogen-Ion Concentration; Immunohistochemistry; Kidney Tubules, Collecting; Macrolides; Male; Potassium, Dietary; Proton Pump Inhibitors; Proton Pumps; Rats; Rats, Sprague-Dawley; Sodium, Dietary; Water-Electrolyte Balance
PubMed: 10894802
DOI: 10.1152/ajprenal.2000.279.1.F195 -
The American Journal of Clinical... Sep 1998Normal adult humans eating Western diets have chronic, low-grade metabolic acidosis, the severity of which is determined in part by the net rate of endogenous... (Comparative Study)
Comparative Study
Normal adult humans eating Western diets have chronic, low-grade metabolic acidosis, the severity of which is determined in part by the net rate of endogenous noncarbonic acid production (NEAP), which varies with diet. To prevent or reverse age-related sequelae of such diet-dependent acidosis (eg, bone and muscle loss), methods are needed for estimating and regulating NEAP. Because NEAP is difficult to measure directly, we sought a simple method to estimate it from diet-composition data. We focused on protein and potassium contents because the production of sulfuric acid from protein metabolism and bicarbonate from dietary potassium salts of organic acids are the major variable components of NEAP. Using steady state renal net acid excretion (RNAE) as an index of NEAP in 141 normal subjects eating 20 different diets, we found by multiple linear regression analysis that RNAE [mEq/d x 10460 kJ diet (mEq/d 2500 kcal)] was predictable (R2 = 0.62) from protein [g/d x 10460 kJ diet (g/d 2500 kcal); positive regression coefficient, P < 0.001] and potassium [mEq/d x 10460 kJ diet (mEq/d x 2500 kcal): negative regression coefficient, P = 0.001] contents, which were not themselves correlated. Among diets, 71% of the variation in RNAE could be accounted for by the ratio of protein (Pro) to potassium (K) content: RNAE = 62Pro/K - 17.9 (r = 0.84, R2 = 0.71, P < 0.001). Thus, by considering both the acidifying effect of protein and the alkalinizing effect of potassium (organic anions), NEAP can be predicted with confidence from the readily available contents of only 2 nutrients in foods. Provisionally, these findings allow estimation and regulation of NEAP through diet modification.
Topics: Acidosis; Adolescent; Adult; Aged; Bicarbonates; Dietary Proteins; Energy Intake; Female; Humans; Male; Middle Aged; Potassium; Predictive Value of Tests; Regression Analysis
PubMed: 9734733
DOI: 10.1093/ajcn/68.3.576 -
Journal of the American Society of... Nov 2000Inward rectifier potassium channels (Kir) play an important role in the K(+) secretion from the kidney. Recently, a new subfamily of Kir, Kir7.1, has been cloned and...
Inward rectifier potassium channels (Kir) play an important role in the K(+) secretion from the kidney. Recently, a new subfamily of Kir, Kir7.1, has been cloned and shown to be present in the kidney as well as in the brain, choroid plexus, thyroid, and intestine. Its cellular and subcellular localization was examined along the renal tubule. Western blot from the kidney cortex showed a single band for Kir7.1 at 52 kD, which was also observed in microdissected segments from the thick ascending limb of Henle, distal convoluted tubule (DCT), connecting tubule, and cortical and medullary collecting ducts. Kir7.1 immunoreactivity was detected predominantly in the DCT, connecting tubule, and cortical collecting duct, with lesser expression in the thick ascending limb of Henle and in the medullary collecting duct. Kir7.1 was detected by electron microscopic immunocytochemistry on the basolateral membrane of the DCT and the principal cells of cortical collecting duct, but neither type A nor type B intercalated cells were stained. The message levels and immunoreactivity were decreased under low-K diet and reversed by low-K diet supplemented with 4% KCl. By the double-labeling immunogold method, both Kir7.1 and Na(+), K(+)-ATPase were independently located on the basolateral membrane. In conclusion, the novel Kir7.1 potassium channel is located predominantly in the basolateral membrane of the distal nephron and collecting duct where it could function together with Na(+), K(+)-ATPase and contribute to cell ion homeostasis and tubular K(+) secretion.
Topics: Animals; Dose-Response Relationship, Drug; Kidney Tubules, Collecting; Male; Microscopy, Immunoelectron; Nephrons; Potassium Channels; Potassium Channels, Inwardly Rectifying; Potassium, Dietary; Rats; Rats, Sprague-Dawley; Tissue Distribution
PubMed: 11053473
DOI: 10.1681/ASN.V11111987 -
Nature Reviews. Nephrology Dec 2013Acidosis affects sodium and potassium excretion, likely via the pH sensitivity of ion transporters. A recent paper shows that β-intercalated cells with deleted...
Acidosis affects sodium and potassium excretion, likely via the pH sensitivity of ion transporters. A recent paper shows that β-intercalated cells with deleted H(+)-ATPase release ATP into urine, which induces the production of prostaglandin E2 (PGE2). PGE2 then reduces sodium absorption in the principal cells of the cortical collecting tubule and increases potassium secretion.
Topics: Animals; Kidney Tubules, Collecting; Potassium, Dietary; Sodium, Dietary; Water-Electrolyte Balance
PubMed: 24189652
DOI: 10.1038/nrneph.2013.235 -
European Journal of Cardiovascular... Aug 2005To determine any differences in the urinary excretion and dietary intake of sodium, potassium, magnesium and calcium intake in three South African ethnic groups, and to... (Comparative Study)
Comparative Study
OBJECTIVES
To determine any differences in the urinary excretion and dietary intake of sodium, potassium, magnesium and calcium intake in three South African ethnic groups, and to assess whether the blood pressure-cation association varies according to ethnic status.
DESIGN
A cross-sectional study of 325 black, white and mixed-ancestry men and women, conveniently sampled in Cape Town. Twenty-four-hour urine samples were collected on three separate occasions for assessment of urinary electrolytes, and three 24-h dietary recalls for the corresponding urine collection times were administered by two trained fieldworkers. Para-amino benzoic acid was used as a marker of the completeness of urine collection.
RESULTS
Mean urinary sodium values equate to a daily salt (sodium chloride) intake of 7.8, 8.5 and 9.5 g in black, mixed-ancestry and white individuals, respectively. In normotensive individuals, black and mixed-ancestry subjects had significantly lower median urinary sodium concentrations than white subjects, but these differences were not evident between black and white hypertensive subjects. No ethnic differences were found for urinary potassium, except for mixed-ancestry normotensive individuals having a lower excretion than white normotensive individuals. Urinary magnesium excretion did not differ across ethnic groups. In both normotensive and hypertensive individuals, urinary calcium concentrations differed between all three groups, with black subjects having the lowest values, approximately less than half those of white subjects.
CONCLUSION
White normotensive subjects in Cape Town have higher habitual intakes of sodium, but also higher calcium intakes than their black and mixed-ancestry counterparts. Dietary differences may contribute to ethnic-related differences in blood pressure.
Topics: Adult; Age Distribution; Aged; Antihypertensive Agents; Biomarkers; Black People; Calcium, Dietary; Cations; Cross-Sectional Studies; Eating; Electrolytes; Female; Humans; Hypertension; Magnesium; Male; Middle Aged; Potassium, Dietary; Predictive Value of Tests; Sex Distribution; Sodium, Dietary; South Africa; White People
PubMed: 16079643
DOI: 10.1097/01.hjr.0000170265.22938.d1