Four novel peptide toxins that act on voltage-gated sodium channels have been isolated from tarantula venoms: ceratotoxins 1, 2, and 3 (CcoTx1, CcoTx2, and CcoTx3) from Ceratogyrus cornuatus and phrixotoxin 3 (PaurTx3) from Phrixotrichus auratus. The pharmacological profiles of these new toxins were characterized by electrophysiological measurements on six cloned voltage-gated sodium channel su...

The possibility that endogenous inhibitors of the sodium pump exist and bind to the cardiac glycoside binding site on Na+,K+-adenosine triphosphatase (ATPase) has been a source of much controversy. Although numerous hormones and inorganic ions that modulate Na+,K+-ATPase activity have been described, most of these affect the sodium pump indirectly by varying the intracellular sodium concentrati...

The Alzheimer BACE1 enzyme cleaves numerous substrates, with largely unknown physiological consequences. We have previously identified the contribution of elevated BACE1 activity to voltage-gated sodium channel Na(v)1.1 density and neuronal function. Here, we analyzed physiological changes in sodium channel metabolism in BACE1-null mice. Mechanistically, we first confirmed that endogenous BACE1...

C-type dorsal root ganglion (DRG) neurons can generate tetrodotoxin-resistant (TTX-R) sodium-dependent action potentials. However, multiple sodium channels are expressed in these neurons, and the molecular identity of the TTX-R sodium channels that contribute to action potential production in these neurons has not been established. In this study, we used current-clamp recordings to compare acti...

'Conventional' (-)-sparteine adducts of lithium and sodium 1,1,1,3,3,3-hexamethyldisilazide (HMDS) were prepared and characterised, along with an unexpected and 'unconventional' hydroxyl-incorporated sodium sodiate, [(-)-sparteine x Na(mu-HMDS)Na x (-)-sparteine](+)[Na(4)(mu-HMDS)(4)(OH)](-)--the complex anion of which is the first inverse crown ether anion.

The intrarenal site of sodium retention was determined by an in vivo micropuncture study in the unilateral model of puromycin aminonucleoside (PAN)-induced proteinuria, which allows the study of a nephrotic and a normal control kidney within the same animal. Sodium delivery to the collecting duct was not different in the two kidneys while the urinary excretion of sodium was 3-fold lower in the ...

Na,K-ATPase generates the driving force for sodium reabsorption in the kidney. Na,K-ATPase functional properties are regulated by small proteins belonging to the FXYD family. In kidney FXYD2 is the most abundant: it is an inhibitory subunit expressed in almost every nephron segment. Its absence should increase sodium pump activity and promote Na(+) retention, however, no obvious renal phenotype...

The fluorescent indicator fura-2 was used to measure cytoplasmic calcium in presynaptic terminals in the crayfish Procambarus clarkii under conditions that raise intracellular sodium to examine whether sodium can elevate intracellular calcium concentration ([Ca2+]i) or prolong its efflux and thus influence the magnitude and duration of posttetanic potentiation (PTP). Sodium was elevated in pres...

All living cells routinely expel Na(+) ions, maintaining lower concentration of Na(+) in the cytoplasm than in the surrounding milieu. In the vast majority of bacteria, as well as in mitochondria and chloroplasts, export of Na(+) occurs at the expense of the proton-motive force. Some bacteria, however, possess primary generators of the transmembrane electrochemical gradient of Na(+) (sodium-mot...

The regulation of the cytosolic free magnesium concentration ([Mg2+]i) is a fundamental cellular process that requires magnesium extruding mechanisms. Here, we present evidence indicating that rat thymocytes are endowed with different Na/Mg exchange systems. Fluxes of magnesium were measured using the fluorescent magnesium indicator magfura-2. Cells were loaded with magnesium using the calcium ...