Interrelation between oxygen consumption and Na-K-ATPase activity in rat renal proximal tubule suspension.
The portion of Na-K-ATPase activity on oxygen consumption was determined in suspensions of rat proximal tubules by monitoring oxygen consumption (QO2) under different metabolic states: in the presence or absence of succinate or lactate (10 mmol/l) and increasing concentrations of ouabain (0.4; 0.8; 1.2 and 1.6 mmol/l). In the metabolic states tested, the ouabain induced decrease of QO2 was identical, which implies a fixed rate between Na-K-ATPase activity and QO2. On the basis of these results, Ki and maximal inhibition rate were determined by Lineweaver-Burk and Eadie-Hofstee plots Ki was 0.67 mmol/l ouabain and the maximal inhibition of QO2 was 77%. This corresponds to an absolute decrease of QO2 of 1,630 mumol O2 . h-1 . g-1 protein. Since this value represents the real portion of Na-K-ATPase on QO2, the activity of Na-K-ATPase can be calculated, yielding an activity of 163 mumol ATP . min-1 . g-1 tubule protein.
Gstraunthaler
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Pfaller
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Kotanko
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D000818:Animals; D007687:Kidney Tubules, Proximal / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism* / Q000648:ultrastructure; D007700:Kinetics; D007773:Lactates / Q000494:pharmacology; D008297:Male; D008855:Microscopy, Electron, Scanning; D010042:Ouabain / Q000494:pharmacology; D010101:Oxygen Consumption / Q000187:drug effects*; D051381:Rats; D011919:Rats, Inbred Strains; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D013386:Succinates / Q000494:pharmacology
D007773:Lactates; D013386:Succinates; D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase