The prokaryotic V-ATPase of Enterococcus hirae, closely related to the eukaryotic enzymes, provides a unique opportunity to study the ion-translocation mechanism because it transports Na(+), which can be detected by radioisotope (22Na(+)) experiments and X-ray crystallography. In this study, we demonstrated that the binding affinity of the rotor ring (K ring) for 22Na(+) decreased approximately...

To measure the influx of Na' and other ions through the lightdependent permeability of photoreceptors, we superfused the isolated retina of the toad, Bufo marinus, with a low-Ca2+ (10-8 M), low-ClRinger's solution containing 0.5 mM ouabain . Under these conditions, the membrane potential of the rod is near zero and there is no light-induced potential change either in the rod or in more proximal...

A low background gamma spectrometer with an Etruscan, 2500 years old lead shield and a muon veto detector were applied to study 22Na and 7Be activity concentration in ground level air aerosol samples collected weekly over the years 2003-2006 in Kraków. Each sample was formed with ca 100 000 m3 of passed air, collected with two parallel ASS-500 high volume air samplers. The results for 40K and 1...

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...

Studies were undertaken in Munich-Wistar rats to assess the influence of changes in filtered bicarbonate (FLHCO3), induced by changes in GFR, on Na+/H+ exchange activity in renal brush border membrane vesicles (BBMV). Whole-kidney and micropuncture measurements of GFR, FLHCO3, and whole-kidney and proximal tubule HCO3 reabsorption (APRHCO3) were coupled with BBMV measurements of H+ gradient-dri...

Treatment of cultured bovine adrenal medullary cells with carbamazepine (CBZ) for 5 days caused an increase in catecholamine secretion induced by veratridine, an activator of voltage-dependent Na+ channels. However, no increase was stimulated by carbachol, an agonist of nicotinic receptors, or by 56 mM K+, a depolarizing agent that activates voltage-dependent Ca++ channels. CBZ (30 microg/ml) t...

Incorporation of the saxitoxin receptor of the sodium channel solubilized with Triton X-100 and purified 250-fold from rat brain into phosphatidylcholine vesicles is described. Fifty to 80% of the saxitoxin receptor sites are recovered in the reconstituted vesicles (KD = 3 nM). Unlike the detergent-solubilized saxitoxin receptor, the reconstituted saxitoxin binding activity is stable to incubat...