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...

Brain capillary endothelial cells play an important role in ion homeostasis of the brain through the transendothelial transport of Na and K. Since little is known about the regulation of ion transport in these cells, we determined the effect of extracellular potassium concentration ([K]o) on the kinetics of the Na,K-pump in isolated cerebral microvessels using both K uptake and Na efflux as mea...

The effects of acute and chronic ethanol treatment on neurotoxin-stimulated 22Na+ uptake and [3H]batrachotoxinin A20-alpha-benzoate binding to neuronal sodium channels were studied in rat forebrain synaptosomes. Fluorescence measurements were used to assess the intrinsic order or fluidity and the sensitivity to ethanol of rat forebrain synaptic plasma membranes at various intervals during and a...

HCO3- exit across the basolateral membrane of the kidney proximal tubule cell is mediated via an electrogenic Na+:HCO3- cotransporter. In these experiments, we have studied the effect of internal pH on the activity of the Na+:HCO3- cotransport system in basolateral membrane vesicles isolated from rabbit renal cortex. Equilibrium thermodynamics predicts that in the presence of constant intravesi...