In this study we have found that L-glutamic acid, as well as being taken up by a Na+-dependent mechanism, will stimulate the uptake of 22Na+ by primary astrocyte cultures from rat brain in the presence of ouabain. By simultaneously measuring the uptake of 22Na+ and L-3H-glutamate a stoichiometry of 2-3 Na+ per glutamate was measured, implying electrogenic uptake. Increasing the medium K+ concen...

The role of the Na(+)-Ca2+ exchanger of heart mitochondria in cellular functioning is not yet clear. The objectives of this study were to investigate the effects of stimulation and inhibition of the Na(+)-Ca2+ exchanger on the matrix free Ca2+ concentration in isolated heart mitochondria and to determine the consequences of these changes on the rate of NADH production via Krebs cycle turnover a...

The sodium/iodide symporter (NIS) mediates active I(-) transport in the thyroid-the first step in thyroid hormone biosynthesis-with a 2 Na(+): 1 I(-) stoichiometry. The two Na(+) binding sites (Na1 and Na2) and the I(-) binding site interact allosterically: when Na(+) binds to a Na(+) site, the affinity of NIS for the other Na(+) and for I(-) increases significantly. In all Na(+)-dependent tran...

Epithelial Na+ channels (ENaC) are inhibited by extracellular Na+, a process referred to as Na+ self-inhibition. We previously demonstrated that mutation of key residues within two furin cleavage consensus sites in alpha, or one site in gamma, blocked subunit proteolysis and inhibited channel activity when mutant channels were expressed in Xenopus laevis oocytes (Hughey RP, Bruns JB, Kinlough C...

THE ROLE OF Na-K-ATPase in the regulation of epithelial cell polarity, adhesion, and migration has been demonstrated. Some of these processes, such as tight junction (TJ) formation, require ion transport function of Na-K-ATPase by its catalytic subunit Na-K. Other functions, such as motility suppression, cell adhesion, and contact inhibition, are mediated by the regulatory subunit Na-K, typical...

Coupled Na+ exit/Ca2+ entry (Na/Ca exchange operating in the Ca2+ influx mode) was studied in giant barnacle muscle cells by measuring 22Na+ efflux and 45Ca2+ influx in internally perfused, ATP-fueled cells in which the Na+ pump was poisoned by 0.1 mM ouabain. Internal free Ca2+, [Ca2+]i, was controlled with a Ca-EGTA buffering system containing 8 mM EGTA and varying amounts of Ca2+. Ca2+ seque...

We report in this paper different modes of Na and K transport in human red cells, which can be inhibited by furosemide in the presence of ouabain. Experimental evidence is provided for inward and outward coupled transport of Na and K, Ki/Ko and Nai/Nao exchange, and uncoupled Na or K efflux. The outward cotransport of Na and K was defined as the furosemide-sensitive (FS) component of Na and K e...

We have found a defect in the ouabain-sensitive Na+, K+-ATPase (Na+ pump, EC 3.6.1.37) of erythrocytes from streptozocin diabetic rats. This defect was accompanied by an increase in cell volume and osmotic fragility and a decrease in the cytosolic K+/Na+ ratio. There was also a doubling in the time needed for diabetic erythrocytes to pass through 4.7-micron channels in a polycarbonate filter. O...

The SLC24 gene family Na+/Ca2+-K+ exchangers (NCKX) are bidirectional plasma membrane transporters whose main function is the extrusion of Ca2+ from the cytosol. In this study, we used human embryonic kidney 293 cells expressing human retinal cone/brain NCKX2 to examine its Na+ affinity and kinetic parameters of Ca2+ transport. With the use of the ionophore gramicidin to control alkali cation c...

electrokinetic remediation is one of the most promising in situ or ex situ processes for decontamination of heavy metals, anions and polar organic compositions from the soil. in this study, we investigated the efficacy of this method in removing mercury from clayey soil (with kaolin to sand weight ratio of 2:1) and from gold mine tailing dam sediment and determined optimum removal conditions. t...