AIMS Contraction of the heart is regulated by electrically evoked Ca(2+) transients (CaTs). H(+) ions, the end products of metabolism, modulate CaTs through direct interactions with Ca(2+)-handling proteins and via Na(+)-mediated coupling between acid-extruding proteins (e.g. Na(+)/H(+) exchange, NHE1) and Na(+)/Ca(2+) exchange. Restricted H(+) diffusivity in cytoplasm predisposes pH-sensitive ...

Mean values of normal arterial pH in different species of fish, amphibians and reptiles at 15 and 25 degrees C, taken from the literature, are negatively correlated with arterial P(CO(2)) and plasma [Na(+)]. At either temperature, the data accord with the hypothesis that extracellular acid-base homeostasis evolved to maintain an optimal pH at particular cell-surface sites that are similar in al...

UNLABELLED To study the regulation of cell pH by ambient pH, carbon dioxide tension (PCO2), and bicarbonate (HCO3), cell pH was measured in the isolated, in vitro microperfused rabbit proximal convoluted tubule using the fluorescent dye (2',7')-bis-(carboxyethyl)-(5,6)-carboxyfluorescein. For the same changes in external pH, changes in [HCO3] and PCO2 affected cell pH similarly ([HCO3]: pHi/pHe...

The basolateral membrane Na+ and Cl(-)-dependent acid-base transport processes were studied in the isolated perfused rabbit S3 proximal straight tubule. Intracellular pH (pHi) was measured with 2'7'-biscarboxyethyl-5,6-carboxyfluorescein (BCECF) and a microfluorometer coupled to the tubule perfusion apparatus. Reduction of basolateral HCO3- from 25 to 5 mM caused pHi to decrease at a rate of 0....

The regulation of proton transport and cytosolic pH was studied in rat papillary collecting duct (PCD) cells in culture using a pH-sensitive fluorescence probe, 2,7-bis-carboxyethyl-5,6-carboxyfluorescein (BCECF). Data were obtained from confluent monolayers grown on glass coverslips and dipped in a HCO3- -free medium, pH 7.40. The resting intracellular pH (pHi) was 7.16 +/- 0.03 (n = 20). When...

The intercalation of poly(allylamine) (PAA) into a synthetic fluoromica (Na-TSM) was studied in order to understand the subsquent process of gold nanoparticle intercalation into the interlayer galleries. The composition and structure of the PAA intercalation compound (PAA/Na-TSM) was strongly influenced by the pH of its synthesis. At pH 3.0, the fully protonated form of the polymer was intercal...

The relationship between sodium transport and the intra- and extracellular pH was examined employing dog kidney epithelial cells (MDCK). Increases in the medium pH led to a stimulation of 22Na+ influx and an inhibition of efflux. Kinetic analysis of the pH effects showed that the apparent Km values for Na+ were substantially altered (28 mM at pH 9 versus 95 mM at pH 6), indicating that H+ and N...

Evidence was found for a Na(+)/H(+) antiport in tonoplast vesicles isolated from barley (Hordeum vulgare L. cv California Mariout 72) roots. The activity of the antiport was observed only in membranes from roots that were grown in NaCl. Measurements of acridine orange fluorescence were used to estimate relative proton influx and efflux from the vesicles. Addition of MgATP to vesicles from a ton...

A 5.9-kb region of the Bacillus subtilis chromosome is transcribed as a single transcript that is predicted to encode seven membrane-spanning proteins. Homologues of the first gene of this operon, for which the designation mrp (multiple resistance and pH adaptation) is proposed here, have been suggested to encode an Na+/H+ antiporter or a K+/H+ antiporter. In the present studies of the B. subti...

To explore the role of the Na-H antiport in essential hypertension, we studied the kinetics of cytosolic pH and external sodium activation of this transport system in platelets from 65 normotensive and essential hypertensive subjects on and off antihypertensive medications. Subjects included both blacks and whites, as well as men and women. The fluorescent dye 2'7-bis(carboxyethyl)-5,6-carboxyf...