A non ouabain-like inhibitor of the sodium pump in uremic plasma ultrafiltrates and urine from healthy subjects.
A non ouabain-like inhibitor of the sodium pump was separated from uremic plasma ultrafiltrates and normal urine. Under the same chromatographic conditions (C18 column and a gradient of acetonitrile as eluant), ouabain was eluted in a fraction different from the inhibitor. Affinity chromatography based on the formation of a complex between Na,K-ATPase and the inhibitor achieved the differentiation ouabain. Without magnesium and sodium phosphate, ouabain could not bind to enzyme whereas the inhibitor did. A study of Na,K-ATPase enzyme kinetics showed the inhibitor was not competitive for K+, which further differentiates it from ouabain. It was uncompetitive for ATP and seemed competitive for Na+. These results indicate that the inhibitor acts inside the cell, unlike ouabain, and thus its action mechanism appears to be original.
Gallice
P M
PM
Laboratoire de Biophysique, Faculté Pharmacie, Marseille, France.
Kovacic
H N
HN
Brunet
P J
PJ
Berland
Y F
YF
Crevat
A D
AD
D000255:Adenosine Triphosphate / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000032:analysis*; D006440:Hemofiltration; D006801:Humans; D007700:Kinetics; D010042:Ouabain; D011188:Potassium / Q000378:metabolism; D012016:Reference Values; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors*; D014511:Uremia / Q000378:metabolism*
D004791:Enzyme Inhibitors; D010042:Ouabain; D000255:Adenosine Triphosphate; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium