Altered Na+-K+ ATPase activity in uraemic adolescents

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Abstract

The Na+-K+ ATPase enzyme plays an essential role in the regulation of cell composition and volume. Enzyme activity itself is regulated by substrate availability and several hormones. In adult uraemic patients red blood cell Na+-K+ ATPase activity is decreased. However, it is unknown if children with uraemia exhibit the same phenomenon. Therefore, in the present study we examined whether endogenous digoxin-like factors (EDLF) and physicochemical membrane properties play a role in the regulation of erythrocyte Na+-K+ ATPase activity in uraemic children and adolescents. Healthy age-matched children were used as controls. Enzyme activity was measured in detergent-pretreated red blood cells and erythrocyte ghosts. Na+-K+ ATPase activity (2204 ± 538 nmol Pi ml erythrocyte-1 h-1 in detergent pretreated erythrocytes; 204 ± 56 nmol Pi mg protein-1 h-1 in ghosts) in adolescents with uraemia was lower compared to controls (3245 ± 362 nmol Pi ml erythrocyte-1 h-1. 266 ± 37 nmol Pi mg protein-1 h-1, p <0.001, p <0.05, respectively). Plasma levels of EDLF were elevated in uraemic patients (0.30 ± 0.05 versus 0.21 ± 0.04 ng ml-1, p <0.01). Furthermore, the membrane lipid component was decreased in patients with uraemia, while the cholesterol/phospholipid ratio and membrane fluidity were similar in both groups. No correlation was found between the decrease in Na+-K+ ATPase and the increase in EDLF concentration and altered membrane lipid components. Our results demonstrate, that similar to the findings of adults, the activity of Na+-K+ ATPase is diminished in uraemic adolescent patients, and that uraemia-associated elevation in EDLF and altered membrane components do not play a role in the down-regulation of Na+-K+ ATPase. Therefore other factors (presence of other inhibitors and/or reduced number of enzyme molecules) should contribute to the lower activity of the Na+-K+ pump.

Original languageEnglish
Pages (from-to)919-922
Number of pages4
JournalActa Paediatrica, International Journal of Paediatrics
Volume85
Issue number8
Publication statusPublished - 1996

Fingerprint

Erythrocytes
Uremia
Erythrocyte Membrane
Enzymes
Membrane Lipids
Detergents
Membrane Fluidity
Membranes
sodium-translocating ATPase
Cell Size
Phospholipids
Proteins
Down-Regulation
Cholesterol
Hormones
digoxin-like factors

Keywords

  • Endogenous digoxin-like factors
  • Fluorescence polarization value
  • Membrane lipid component
  • Na-K ATPase
  • Uraemia

ASJC Scopus subject areas

  • Pediatrics, Perinatology, and Child Health

Cite this

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title = "Altered Na+-K+ ATPase activity in uraemic adolescents",
abstract = "The Na+-K+ ATPase enzyme plays an essential role in the regulation of cell composition and volume. Enzyme activity itself is regulated by substrate availability and several hormones. In adult uraemic patients red blood cell Na+-K+ ATPase activity is decreased. However, it is unknown if children with uraemia exhibit the same phenomenon. Therefore, in the present study we examined whether endogenous digoxin-like factors (EDLF) and physicochemical membrane properties play a role in the regulation of erythrocyte Na+-K+ ATPase activity in uraemic children and adolescents. Healthy age-matched children were used as controls. Enzyme activity was measured in detergent-pretreated red blood cells and erythrocyte ghosts. Na+-K+ ATPase activity (2204 ± 538 nmol Pi ml erythrocyte-1 h-1 in detergent pretreated erythrocytes; 204 ± 56 nmol Pi mg protein-1 h-1 in ghosts) in adolescents with uraemia was lower compared to controls (3245 ± 362 nmol Pi ml erythrocyte-1 h-1. 266 ± 37 nmol Pi mg protein-1 h-1, p <0.001, p <0.05, respectively). Plasma levels of EDLF were elevated in uraemic patients (0.30 ± 0.05 versus 0.21 ± 0.04 ng ml-1, p <0.01). Furthermore, the membrane lipid component was decreased in patients with uraemia, while the cholesterol/phospholipid ratio and membrane fluidity were similar in both groups. No correlation was found between the decrease in Na+-K+ ATPase and the increase in EDLF concentration and altered membrane lipid components. Our results demonstrate, that similar to the findings of adults, the activity of Na+-K+ ATPase is diminished in uraemic adolescent patients, and that uraemia-associated elevation in EDLF and altered membrane components do not play a role in the down-regulation of Na+-K+ ATPase. Therefore other factors (presence of other inhibitors and/or reduced number of enzyme molecules) should contribute to the lower activity of the Na+-K+ pump.",
keywords = "Endogenous digoxin-like factors, Fluorescence polarization value, Membrane lipid component, Na-K ATPase, Uraemia",
author = "B. V{\'a}s{\'a}rhelyi and P. Sallay and E. Balog and G. Reusz and T. Tulassay",
year = "1996",
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T1 - Altered Na+-K+ ATPase activity in uraemic adolescents

AU - Vásárhelyi, B.

AU - Sallay, P.

AU - Balog, E.

AU - Reusz, G.

AU - Tulassay, T.

PY - 1996

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N2 - The Na+-K+ ATPase enzyme plays an essential role in the regulation of cell composition and volume. Enzyme activity itself is regulated by substrate availability and several hormones. In adult uraemic patients red blood cell Na+-K+ ATPase activity is decreased. However, it is unknown if children with uraemia exhibit the same phenomenon. Therefore, in the present study we examined whether endogenous digoxin-like factors (EDLF) and physicochemical membrane properties play a role in the regulation of erythrocyte Na+-K+ ATPase activity in uraemic children and adolescents. Healthy age-matched children were used as controls. Enzyme activity was measured in detergent-pretreated red blood cells and erythrocyte ghosts. Na+-K+ ATPase activity (2204 ± 538 nmol Pi ml erythrocyte-1 h-1 in detergent pretreated erythrocytes; 204 ± 56 nmol Pi mg protein-1 h-1 in ghosts) in adolescents with uraemia was lower compared to controls (3245 ± 362 nmol Pi ml erythrocyte-1 h-1. 266 ± 37 nmol Pi mg protein-1 h-1, p <0.001, p <0.05, respectively). Plasma levels of EDLF were elevated in uraemic patients (0.30 ± 0.05 versus 0.21 ± 0.04 ng ml-1, p <0.01). Furthermore, the membrane lipid component was decreased in patients with uraemia, while the cholesterol/phospholipid ratio and membrane fluidity were similar in both groups. No correlation was found between the decrease in Na+-K+ ATPase and the increase in EDLF concentration and altered membrane lipid components. Our results demonstrate, that similar to the findings of adults, the activity of Na+-K+ ATPase is diminished in uraemic adolescent patients, and that uraemia-associated elevation in EDLF and altered membrane components do not play a role in the down-regulation of Na+-K+ ATPase. Therefore other factors (presence of other inhibitors and/or reduced number of enzyme molecules) should contribute to the lower activity of the Na+-K+ pump.

AB - The Na+-K+ ATPase enzyme plays an essential role in the regulation of cell composition and volume. Enzyme activity itself is regulated by substrate availability and several hormones. In adult uraemic patients red blood cell Na+-K+ ATPase activity is decreased. However, it is unknown if children with uraemia exhibit the same phenomenon. Therefore, in the present study we examined whether endogenous digoxin-like factors (EDLF) and physicochemical membrane properties play a role in the regulation of erythrocyte Na+-K+ ATPase activity in uraemic children and adolescents. Healthy age-matched children were used as controls. Enzyme activity was measured in detergent-pretreated red blood cells and erythrocyte ghosts. Na+-K+ ATPase activity (2204 ± 538 nmol Pi ml erythrocyte-1 h-1 in detergent pretreated erythrocytes; 204 ± 56 nmol Pi mg protein-1 h-1 in ghosts) in adolescents with uraemia was lower compared to controls (3245 ± 362 nmol Pi ml erythrocyte-1 h-1. 266 ± 37 nmol Pi mg protein-1 h-1, p <0.001, p <0.05, respectively). Plasma levels of EDLF were elevated in uraemic patients (0.30 ± 0.05 versus 0.21 ± 0.04 ng ml-1, p <0.01). Furthermore, the membrane lipid component was decreased in patients with uraemia, while the cholesterol/phospholipid ratio and membrane fluidity were similar in both groups. No correlation was found between the decrease in Na+-K+ ATPase and the increase in EDLF concentration and altered membrane lipid components. Our results demonstrate, that similar to the findings of adults, the activity of Na+-K+ ATPase is diminished in uraemic adolescent patients, and that uraemia-associated elevation in EDLF and altered membrane components do not play a role in the down-regulation of Na+-K+ ATPase. Therefore other factors (presence of other inhibitors and/or reduced number of enzyme molecules) should contribute to the lower activity of the Na+-K+ pump.

KW - Endogenous digoxin-like factors

KW - Fluorescence polarization value

KW - Membrane lipid component

KW - Na-K ATPase

KW - Uraemia

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