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Query: UMLS:C0085580 (essential hypertension)
 14,686 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The content of calcium bound to the erythrocyte membrane and the effect of intracellular calcium concentration on the activity of Na+, K+-ATPase in the reconstituted erythrocytes were studied in 20 patients with essential hypertension and in 20 individuals with normal pressure. In incubation of the erythrocytes in a solution containing EDTA much more calcium is removed from the outer surface of their membrane in patients with essential hypertension than in the control group (60 +/- 5 mEq/l and 41 +/- 3 mEq/l, respectively). When the intracellular calcium concentration varies from 0 to 500 mumol/l, which corresponds to a rise in the free calcium (Ca2f+-3) concentration to 41 mumol/l, a difference in the changes of Na+, K+-ATPase activity of the reconstituted erythrocytes is noted. When intracellular calcium concentration is 50 mumol/l (Ca2f+-3 mumol/l), ATP-ase activity in patients with essential hypertension is 21% less than that in individuals with normal pressure (P less than 0.005). The authors explain the difference in the kinetics of Na+, K+-ATPase changes by the different degree of calcium depletion of the inner surface of the erythrocyte membrane in relatively low Ca2f+ values in the internal medium. The data obtained are evidence of the altered calcium-binding capacity of the erythrocyte membrane, which may cause the increased permeability of the erythrocyte membrane to sodium and potassium ions in patients with essential hypertension, which the authors had revealed earlier. The authors consider the revealed changes to be a fragment of a more extensive membrane defect which may be the principal cause of activation of the servomechanisms which maintain arterial pressure.
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PMID:[Role of membrane-bound calcium in the changes of ion permeability and Na+, 5+ and ATPase activity of the erythrocytes in hypertension]. 14 18

Increased sodium concentration and high influx of Na22 are reported in erythrocytes of patients with essential hypertension. It was speculated, that these findings are due to a disturbed transport for sodium across red cell membranes. We found a significantly increased activity of the ouabainsensitive Na-K-ATP'ase in red cell ghosts of 27 patients with essential hypertension compaired with 32 normotensive controls. There existed no difference in Mg-ATP'ase-activity between the two groups. These findings suggest an increased activity of the Na-pump in red cell membranes of patients with essential hypertension.
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PMID:[Sodium-potassium-adenosine triphosphatase-activity in red cell ghosts of patients with essential hypertension (author's transl)]. 21 37

An assessment of the ATPase functions of erythrocyte membrane of newly identified subjects having essential hypertension shows that Na+,K(+)-ATPase activity is higher in normal membranes than in membranes of individuals with essential hypertension. A study of the dependence of the enzyme on ATP in the presence of non-limiting concentrations of Na+ (120 mM) and Mg2+ (3 mM) shows that the pump in the membranes of hypertensive individuals, like that of normal humans, is easily saturable by ATP (greater than or equal to 2 microM). Analysis of the results of kinetic studies on the enzyme, in the presence of 5 mM K+, using the Hanes plot, reveals that, although the affinity (Km) of the pump for ATP is unaffected in essential hypertension, its maximum velocity (Vmax) is lower than in normal membranes. Even though the reason for a reduced sodium pump function in essential hypertension is not yet clear, it may not be unconnected with the presence of an endogenous inhibitor or with genetic or diet-induced membrane defects, as previously proposed by other workers in this area of research.
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PMID:Erythrocyte membrane ouabain-sensitive Na+, K(+)-ATPase of hypertensive Nigerians. 165 90

We have investigated hypertension-associated alterations in intracellular cations in the kidney by measuring intracellular pH, free Mg2+, free Ca2+, and Na+ concentrations in perfused normotensive and hypertensive rat (8-14 weeks old) kidneys using 31P, 19F, and double quantum-filtered (DQ) 23Na NMR. The effects of both anoxia and ischemia on the 23Na DQ signal confirmed its ability to detect changes in intracellular Na+. However, there was a sizable contribution of the extracellular Na+ to the 23Na DQ signal of the kidney. The intracellular free Ca2+ concentration, measured using 19F NMR and 5,5'difluoro-1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid, also increased dramatically during ischemia; the increase could be partly reversed by reperfusion. No significant differences were found between normotensive and hypertensive kidneys in the ATP level, intracellular pH, intracellular free Mg2+, and the 23Na DQ signal or in the extent of the extracellular contribution to the 23Na DQ signal. Oxygen consumption rates were also similar for the normotensive (5.02 +/- 0.46 mumol of O2/min/g) and hypertensive (5.47 +/- 0.42 mumol O2/min/g) rat kidneys. The absence of a significant difference in intracellular pH, Na+ concentration, and oxygen consumption between normotensive and hypertensive rat kidneys suggests that an alteration in the luminal Na+/H+ antiport activity in hypertension is unlikely. However, a highly significant increase (64%, p less than 0.01) in free Ca2+ concentration was found in perfused kidneys from hypertensive rats (557 +/- 48 nM, blood pressure = 199 +/- 5 mmHg, n = 6) compared with normotensive rats (339 +/- 21 nM, blood pressure = 134 +/- 6, n = 4) indicating altered renal calcium homeostasis in essential hypertension. An increase in intracellular free Ca2+ concentration without an accompanying change in the intracellular Na+ suggests, among many possibilities, that the Ca2+/Mg(2+)-ATPase may be inhibited in the hypertensive renal tissue.
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PMID:Multinuclear NMR studies of intracellular cations in perfused hypertensive rat kidney. 174 Apr 16

We have employed 31P nuclear magnetic resonance (NMR) spectroscopy to examine the relationship between cytosolic free Mg2+ ([Mg2+]in), intracellular pH, high energy phosphates, and genetic hypertension using the Wistar-Kyoto rat (WKY) as a control and the spontaneously hypertensive rat (SHR) as a model for essential hypertension. The mean systolic blood pressures (measured using the tail cuff method) of control and hypertensive rats (aged 7 to 12 weeks) were 113 +/- 4 mm Hg (mean +/- 2 SE, n = 14) and 162 +/- 5 mm Hg (mean +/- 2 SE, n = 17), respectively. Intracellular free Mg2+ levels were significantly depleted in the isolated Langendorff perfused hypertensive rat hearts (452 +/- 39 mumol/L, mean +/- 2 SE, n = 17) compared to control hearts (756 +/- 52 mumol/L, n = 14); however, intracellular pH did not differ in the SHR hearts (7.02 +/- 0.03, mean +/- 2 SE, n = 7) compared with controls (7.03 +/- 0.03, n = 7). Although we could not demonstrate a statistically significant difference in the levels of P-creatine or ATP, intracellular Pi was two-fold higher (5.71 +/- 2.28 mmol/L v 2.92 +/- 0.66 mmol/L, n = 4) and the phosphorylation potential, [MgATP]/[MgADP][Pi], was correspondingly lower (3.0 X 10(4) +/- 1.6 x 10(4) v 8.3 X 10(4) +/- 1.4 X 10(4) (mol/L)-1, n = 4) in SHR compared to WKY hearts. These data demonstrate free magnesium depletion in heart muscle and indicate an alteration in cardiac bioenergetics in essential hypertension.
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PMID:Intracellular free magnesium and high energy phosphates in the perfused normotensive and spontaneously hypertensive rat heart. A 31P NMR study. 202 44

The use of Beckmann LS-7000 liquid scintillation spectrometer enabled us to develop a rapid and reproducible technique for the enzymatic microdosage of ATP by means of the bioluminescence reaction of the luciferin-luciferase system from the firefly. Changes of ATP concentration in the plasma, erythrocytes and cerebrospinal fluid of the hypertensive subjects as compared to the control ones have been revealed by means of this method. According to our results ATP concentration significantly increases in the plasma and cerebrospinal fluid and slightly modifies in the erythrocytes of the hypertensive as compared with control subjects. Correlation of data concerning the variation of ATP distribution in the different compartments (plasma, erythrocytes, cerebrospinal fluid) with those related to Na and K content in hypertensive and control subjects seems to be useful for some remarks on the molecular mechanisms in the essential hypertension.
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PMID:Studies concerning ATP dynamics in essential hypertension. 208 13

During the last 15 years an increasing experimental support for the hypothesis of the involvement of the cell membrane alterations in the pathogenesis of the essential hypertension has been evidentiated. Four key factors have been revealed as involved in the generation of sodium-dependent hypertension: 1) genetic or acquired defect in renal sodium excretion; 2) dietary sodium intake; 3) natriuretic hormone as sodium inhibitor; 4) sodium for calcium exchange in smooth muscle and plasma membranes. Taking into account the fact that all of them could be responsible for the cell shape modifications at molecular level and considering also the fact that the membrane defects are present only in the primary forms of hypertension, a comparative study of erythrocyte shape modifications between control and hypertensive human subjects has been performed. The shapes of cells were investigated by an inverted light microscope after their sedimentation on glass cover slips. The computer analysis of images revealed a significant difference (p less than 0.001) between the control and hypertensive subjects as concern the echinocytes/total cells ratios, concluding that a shape modification of erythrocytes is occurring in case of essential hypertension. The high rate of transformation of biconcave disks into echinocytes found in case of hypertension is correlated with ATP pool decreasing that we have previously observed at the same disease. The results are discussed in terms of molecular membrane properties of the mammalian erythrocytes and their structure proteins/lipids organization. A model of cell shape transformation upon ATP pool control is presented for the hypertensive disease.
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PMID:Erythrocyte molecular shape modifications in the primary hypertension. 213 39

We have utilized multinuclear NMR spectroscopy to examine the relationship between cytosolic free Ca2+ ([Ca2+]in), free Mg2+ ([Mg2+]in) and intracellular Na+ ([Na+]in) levels of the intact thoracic aorta and primary hypertension using the Wistar-Kyoto and Sprague-Dawley rats as controls and the spontaneously hypertensive rat as a model for genetic hypertension. Cytosolic free [Ca2+] was measured using 19F NMR of the intracellular Ca2+ indicator 5,5'-difluoro-1,2-bis-(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid, free [Mg2+] using the 31P resonances of intracellular ATP, and intracellular [Na+] by 23Na NMR in combination with the extracellular shift reagent dysprosium tripolyphosphate. We have found that both the [Na+]in and [Ca2+]in levels were significantly increased in the hypertensive animals relative to normotensive controls (p less than 0.01). Mean systolic blood pressures (using tail cuff method) of control and hypertensive rats were 123 +/- 8 mm Hg (mean +/- 2 S.E., n = 7) and 159 +/- 6 mm Hg (mean +/- 2 S.E., n = 7), respectively. [Na+]in and [Ca2+]in were 21.9 +/- 6.4 mM (mean +/- 2 S.E., n = 7) and 277 +/- 28 nM (mean +/- 2 S.E., n = 5) for the spontaneously hypertensive rats versus 10.1 +/- 1.8 mM (mean +/- 2 S.E., n = 7) and 151 +/- 26 nM (mean +/- 2 S.E., n = 5) for control rats, respectively. A slight difference observed between intracellular free Mg2+ levels in hypertensives (180 +/- 38 microM, mean +/- 2 S.E., n = 4) and controls (246 +/- 76 microM, mean +/- 2 S.E., n = 4) was not statistically significant (p greater than 0.1). These data indicate alterations in the cell membrane ion transport function of the aortic smooth muscle in primary hypertension.
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PMID:NMR measurement of cytosolic free calcium, free magnesium, and intracellular sodium in the aorta of the normal and spontaneously hypertensive rat. 229 35

A 3-fold higher concentration of "endogenous digitalis" is found in the serum of patients with essential hypertension than in the serum of normotensives, whose concentration was determined in 22 normotensive probands by an receptor assay using isolated (Na+ + K+)-ATPase as 76.3 +/- 9.3 nM ouabain equivalents. Since the concentration of "endogenous digitalis" was 7-19 fold higher in 2 patients, who had become uremic due to a malignant hypertension and since their serum levels fell 3-fold by hemodialysis, the hemofiltrate was used for partial purification of the substance. This was possible by hydrophobic chromatography on Amberlite XAD-2, octadecyl-coated silica gel, anion exchange chromatography and affinity chromatography on membrane-bound (Na+ + K+)-ATPase. The partially purified substance behaved like the material described by Cloix et al. (1985) Biochem. Biophys. Res. Commun. 131:1234-1240 and competed with digoxin for digoxin antibodies. Ascorbic acid isolated on the search for an inhibitor of (Na+ + K+)-ATPase from beef brain inhibited [3H]ouabain binding due to a decrease of the ouabain binding sites by a reduction of a group within the ATP binding site of the enzyme. Unsaturated fatty acids claimed to be "endogenous digitalis (Tamura et al. [1985] J. Biol. Chem. 260:9672-9677)" also lowered the capacity of the cardiac glycoside binding site but did not compete with ouabain.
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PMID:Sodium pump inhibitor in the serum of patients with essential hypertension and its partial purification from hemofiltrate. 243 45

An increase in free cytosolic calcium content has been reported in essential hypertension. Since within the membrane, the phosphoinositides participate in the control of cell calcium homeostasis, we investigated whether impaired phosphoinositide metabolism could account for the calcium handling abnormality observed in hypertensives. In erythrocyte membranes of hypertensives the activity of kinases involved in polyphosphoinositide formation appears to be impaired and could be related to the alteration in calcium handling binding capacity and ATP-dependent calcium transport. In platelets of hypertensives, the hyperactivity of phospholipase C (observed even in the absence of calcium in the external medium) is likely to be responsible for the hypersensitivity of cells to various agonists. These observations are consistent with the hypothesis that in cells from hypertensives, a membrane defect linked to phosphoinositide metabolism is involved in the overall calcium handling defect.
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PMID:Defective phosphoinositide metabolism in primary hypertension. 283 Oct 75


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