The role of potassium in the regulation of adenosine production by ATP-diphosphohydrolase on the endothelial cell membrane.
Endothelial cells have ectonucleotidases that catabolize extracellular nucleotides and are sensitive to the presence of cations. Our aim was to determine whether the metabolism of extracellular nucleotides is influenced by exposure of endothelial cells to high potassium relevant to human pathophysiology. Human umbilical vein endothelial cells were incubated with 25 mM potassium and without potassium. The metabolism of radioactive substrates was measured and activities were 7.0+/-1.3 and 12.2+/-1.4 microM P/h/mg of protein with and without potassium. Also incubation with membrane pellet from endothelial cells was used, this assay showed 15.5+/-1.9 and 20.9+/-0.7 microM P/ h/mg of protein with and without potassium, respectively. HPLC analysis of supernatant showed that AMP production was lower in the presence of 25 mM potassium. Analysis of different potassium levels showed that a progressive reduction occurred above 10 mM potassium. We conclude those potassium levels above 10 mM, which can be found in ischemia, inhibit the catabolism of extracellular adenine nucleotides by the ectonucleotidases of endothelial cells and may thus modify the pathophysiology of ischemia-reperfusion injury.
Garcia Soriano
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Departamento de Clinica Medica da Faculdade de Medicina da Universidade de Sao Paulo, Sao Paulo, Brazil.
Seguro
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Tadeu Velasco
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D000241:Adenosine / Q000378:metabolism*; D001081:Apyrase / Q000378:metabolism*; D002412:Cations / Q000494:pharmacology; D002478:Cells, Cultured; D002851:Chromatography, High Pressure Liquid; D004730:Endothelium, Vascular / Q000201:enzymology*; D007511:Ischemia / Q000201:enzymology; D008565:Membrane Proteins / Q000378:metabolism; D011188:Potassium / Q000494:pharmacology*; D014469:Umbilical Arteries
D002412:Cations; D008565:Membrane Proteins; D001081:Apyrase; D000241:Adenosine; D011188:Potassium