The Na/K ratio is considered to be a useful index, the monitoring of which allows an effective Na reduction and K increase, because practical methods (self-monitoring devices and reliable individual estimates from spot urine) are available for assessing these levels in individuals. An intervention trial for lowering the Na/K ratio has demonstrated that a reduction of the Na/K ratio mainly invol...

Because in outer medullary collecting ducts (OMCD) of K(+)-depleted rats, K+ secretion is abolished, whereas Na+, K(+)-ATPase, which energizes this secretion, is markedly stimulated, it has been proposed that Na+, K(+)-ATPase was mislocated to the apical cell membrane and energized K+ reabsorption. This hypothesis has been supported by paradoxical effects of ouabain in K(+)-depleted compared wi...

To investigate whether nongastric H+-K+-ATPases transport Na+ in exchange for K+ and whether different beta-isoforms influence their transport properties, we compared the functional properties of the catalytic subunit of human nongastric H+-K+-ATPase, ATP1al1 (AL1), and of the Na+-K+-ATPase alpha1-subunit (alpha1) expressed in Xenopus oocytes, with different beta-subunits. Our results show that...

The handling of Na(+) and K(+) loads was investigated in isolated Malpighian tubules and in whole mosquitoes of Aedes aegypti. Isolated Malpighian tubules bathed in Na(+)-rich Ringer solution secreted Na(+)-rich fluid, and tubules bathed in K(+)-rich Ringer solution secreted K(+)-rich fluid. Upon Na(+) loading the hemolymph, the mosquito removed 77% the injected Na(+) within the next 30 min. Th...

To elucidate the role of intracellular Na(+) kinetics in the mechanism for ischemic preconditioning (IPC), we measured intracellular Na(+) concentration ([Na(+)](i)) using (23)Na-magnetic resonance spectroscopy in isolated rat hearts. IPC significantly delayed the initial [Na(+)](i) increase (d[Na(+)](i)/dt) compared with non-IPC control, resulting in attenuation of Na(+) accumulation (Delta[Na...

PURPOSE To determine the stoichiometry of Na+,K+,Cl- cotransport in fetal human nonpigmented ciliary epithelial cells and the effect of forskolin, an adenylyl cyclase activator, on Na+,K+,Cl- cotransport. METHODS 86Rb+ as a marker for K+ was used to study ouabain-insensitive, bumetanide-sensitive 86Rb+ uptake in cultured human nonpigmented epithelial (NPE) monolayers. RESULTS The dependence...

Following a recent demonstration that H,K-ATPase can active transport Na+ at a low rate (Polvani, C., Sachs, G., and Blostein, R. (1989) J. Biol. Chem. 264, 17854-17859), we have looked for and found effects of Na+ ions on the conformational state of gastric H,K-ATPase labeled with fluorescein isothiocyanate. Na+ ions reverse the K(+)-induced quench of the fluorescein fluorescence and somewhat ...