Ionic dependence of active Na-K transport: clamping of cellular Na/sup +/ with monensin

Journal Article · Wed Jul 01 04:00:00 EDT 1987 · Am. J. Physiol.; (United States)

OSTI ID:6207810

Haber, R S; Pressley, T A; Loeb, J N; Ismail-Beigi, F

The Na/sup +/ ionophore monensin was used to study the Na/sup +/- and K/sup +/-dependence of ouabain-inhibitable /sup 86/Rb/sup +/ uptake in ARL 15 cells, a rat liver cell line. Graded concentrations of monensin rapidly induced incremental elevations of cellular Na/sup +/ that were stable for up to 2 h. In experiments in which cellular Na/sup +/ was thus clamped at various levels, the activation curve for ouabain-inhibitable /sup 86/Rb/sup +/ uptake as a function of intracellular Na/sup +/ was found to be steepest near basal Na/sup +/ levels (Hill coefficient /congruent/ 2.4), indicating that these cells can respond to relatively large changes in passive Na/sup +/ entry by increasing the rate of Na-K pump function with only minimal increases in cellular Na/sup +/. Exposure of cells to monensin also permitted examination of the extracellular-K/sup +/ dependence of ouabain inhibitable /sup 86/Rb/sup +/ uptake in presence of saturating intracellular Na/sup +/ and yielded a Hill coefficient of approx. 1.5. The rate of ATP hydrolysis calculated from measurements of the maximal rate of ouabain-inhibitable /sup 86/Rb/sup +/ uptake in intact cells was similar to the enzymatic V/sub max/ of the Na/sup +/-K/sup +/-ATPase in cell lysates, suggesting that the Na/sup +/-K/sup +/-ATPase activity in these broken-cell preparations closely reflects the functional transport capacity of the Na-K pump.

• Research Organization: Columbia Univ., New York, NY (USA)
• OSTI ID: 6207810
• Journal Information: Am. J. Physiol.; (United States), Journal Name: Am. J. Physiol.; (United States) Vol. 253:1; ISSN AJPHA
• Country of Publication: United States
• Language: English

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59 BASIC BIOLOGICAL SCIENCES
ACID ANHYDRASES
ALKALI METAL COMPOUNDS
ALKALI METAL ISOTOPES
ATP
ATP-ASE
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
CATIONS
CHARGED PARTICLES
CHLORIDES
CHLORINE COMPOUNDS
DAYS LIVING RADIOISOTOPES
DOSE-RESPONSE RELATIONSHIPS
ENZYMES
HALIDES
HALOGEN COMPOUNDS
HOURS LIVING RADIOISOTOPES
HYDROLASES
INTERMEDIATE MASS NUCLEI
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ISOMERIC TRANSITION ISOTOPES
ISOTOPES
KINETICS
MEMBRANE TRANSPORT
MINUTES LIVING RADIOISOTOPES
NUCLEI
NUCLEOTIDES
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
PHOSPHOHYDROLASES
POTASSIUM 42
POTASSIUM CHLORIDES
POTASSIUM COMPOUNDS
POTASSIUM ISOTOPES
RADIOISOTOPES
REACTION KINETICS
RUBIDIUM 86
RUBIDIUM CHLORIDES
RUBIDIUM COMPOUNDS
RUBIDIUM ISOTOPES
SODIUM COMPOUNDS