Spinal cord astrocytes display a high density of voltage-gated Na+ channels. To study the contribution of Na+ influx via these channels to Na+ homeostasis in cultured spinal cord astrocytes, we measured intracellular Na+ concentration ([Na+]i) with the fluorescent dye sodium-binding benzofuran isophthalate. Stellate and nonstellate astrocytes, which display Na+ currents with different propertie...

  In a three-year (2004-2006), field experiment, we aimed to study changes in leaf physiological traits (leaf water potential-Ψleaf, leaf water content-LWC, carbon isotope discrimination-Δ, specific leaf area-SLA, chlorophyll content as assessed by SPAD and modified SPAD-MSPAD) and elemental composition (K, Na, Ca, Mg, K/Na, Ca/Mg, total leaf salinity-TLS) of sugar beets (cv. Rizor) grown unde...

The effects of insulin and ouabain on 22Na efflux and net Na loss were examined in frog sartorius muscles. After removal of ouabain, 22Na efflux which had been inhibited by ouabain remained at the inhibited level for more than 2 hr. In ouabain-free solution, insulin stimulated the Na efflux from ouabain-preincubated muscles. The stimulating effect of insulin on 22Na efflux was completely blocke...

Mechanisms that contribute to Na+ influx during and immediately after 5 min anoxia were investigated in cultured rat hippocampal neurons loaded with the Na+-sensitive fluorophore sodium-binding benzofuran isophthalate. During anoxia, an influx of Na+ in the face of reduced Na+,K+-ATPase activity caused a rise in [Na+]i. After the return to normoxia, Na+,K+-ATPase activity mediated the recovery ...

Decades ago, it was proposed that Na transport in cardiac myocytes is modulated by large changes in cytoplasmic Na concentration within restricted subsarcolemmal spaces. Here, we probe this hypothesis for Na/K pumps by generating constitutive transsarcolemmal Na flux with the Na channel opener veratridine in whole-cell patch-clamp recordings. Using 25 mM Na in the patch pipette, pump currents d...

Ouabain-sensitive uncoupled Na+ efflux has been studied in human, pig, and rat red cells and in vesicles containing reconstituted kidney Na+/K+ pumps obtained from these same species. The red cells from the different species gave qualitatively similar results; the uncoupled Na+ efflux was 15-30% of the Na+/K+ exchange rate, and this flux was inhibited at 5 mM extracellular Na+ (Na+o). At higher...

OBJECTIVE To investigate whether hypertrophy in the dog with chronic atrioventricular block (CAVB) alters [Na+]i and Na/K-pump function of ventricular myocytes. METHODS We measured the [Na+]i dependence of the Na/K pump current, I(p). This relation was used as a calibration curve for [Na+]i based on I(p). We measured I(p) at the time of access and extrapolated [Na+] at the pump sites, i.e. su...

Reverse-mode activity of the Na(+)/Ca(2+) exchanger (NCX) has been previously shown to play a prominent role in excitation-contraction coupling in the neonatal rabbit heart, where we have proposed that a restricted subsarcolemmal domain allows a Na(+) current to cause an elevation in the Na(+) concentration sufficiently large to bring Ca(2+) into the myocyte through reverse-mode NCX. In the pre...

BACKGROUND Patients contracting influenza A(H7N9) infection often developed severe disease causing respiratory failure. Neuraminidase (NA) inhibitors (NAIs) are the primary option for treatment, but information on drug-resistance markers for influenza A(H7N9) is limited. METHODS Four NA variants of A/Taiwan/1/2013(H7N9) virus containing a single substitution (NA-E119V, NA-I222K, NA-I222R, or ...

Two ionophores (monensin and gramicidin) that carry Na+ into 3T3 cells markedly enhance the rate of 86Rb+ uptake. Ouabain prevents both ionophores from increasing 86Rb+ uptake, indicating that the ionophores activate the Na+,K+ pump. Measurements of 86Rb+ uptake and cell Na+ and K+ over a range of monensin concentrations show that the activity of the Na+,K+ pump in 3T3 cells is limited by the s...