We report direct (23)Na NMR observation for the presence of mixed cations (Na(+)/K(+), Na(+)/Rb(+), Na(+)/Sr(2+)) inside the G-quadruplex channel formed by the self-association of guanosine 5'-monophosphate at pH 8.

Members of the SLC20 family or type III Na(+) -coupled P(i) cotransporters (PiT-1, PiT-2) are ubiquitously expressed in mammalian tissue and are thought to perform a housekeeping function for intracellular P(i) homeostasis. Previous studies have shown that PiT-1 and PiT-2 mediate electrogenic P(i) cotransport when expressed in Xenopus oocytes, but only limited kinetic characterizations were mad...

We measured unidirectional ion fluxes of fish collected directly from the Rio Negro, an extremely dilute, acidic blackwater tributary of the Amazon. Kinetic analysis of Na(+) uptake revealed that most species had fairly similar J(max) values, ranging from 1,150 to 1,750 nmol g(-1) h(-1), while K(m) values varied to a greater extent. Three species had K(m) values <33 micromol L(-1), while the re...

A high-fat/high-protein diet has been reported to promote colon cancer by increasing luminal bile acid and ammonia concentrations, whereas butyrate, calcium, and low colonic pH may have protective effects. In this study, bromodeoxyuridine labeling of colonic epithelium was investigated after incubating biopsies from the ascending colon of 70 patients with HCl (20 mM, pH 6.0), butyric acid (H-BU...

The influence of the dispersion of pH and concentration of chemicals on zeta potential of kaolinite were investigated. Adding the cationic species led to an increase of the zeta potential, contrary to measuring done in water. The results proved that even a very low concentration of the cationic species (0.001 mol/L) causes a remarkable change of the zeta potential. The zeta potential of the kao...

The choroid plexus epithelium (CPE) secretes the major fraction of the cerebrospinal fluid (CSF). The Na(+)-HCO(3)(-) transporter Ncbe/Nbcn2 in the basolateral membrane of CPE cells is important for Na(+)-dependent pH(i) increases and probably for CSF secretion. In the current study, the anion transport inhibitor DIDS had no effect on the residual pH(i) recovery in acidified CPE from Ncbe/Nbcn2...

We studied the regulation of intracellular pH (pH i ) in single cultured astrocytes passaged once from the hippocampus of the rat, using the dye 2 9 ,7 9 -biscarboxyethyl-5,6-carboxyfluorescein (BCECF) to monitor pH i . Intrinsic buffering power ( b I ) was 10.5 mM (pH unit) 2 1 at pH i 7.0, and decreased linearly with pH i ; the best-fit line to the data had a slope of 2 10.0 mM (pH unit) 2 2 ...

The purpose of this study was to investigate the direct effect of NH(3)/NH on mouse epithelial Na(+) channels (mENaC) expressed in Xenopus oocytes. Two-electrode voltage-clamp and ion-selective microelectrodes were used to measure the Na(+) current, intracellular pH (pH(i)), and ion activities in oocytes expressing mENaC. In oocytes expressing mENaC, removal of external Na(+) reversibly hyperpo...

Previous studies have demonstrated a raised Na(+) content in leucocytes isolated from women with pre-eclampsia. Increased Na(+)/H(+) exchanger activity is one membrane transport abnormality that may contribute to this phenomenon and may be implicated in the abnormal volume homoeostasis and hypertension associated with the disease. Increased Na(+)/H(+) exchanger activity has been documented in n...