The epithelial Na(+) channel (ENaC) is tightly regulated by sodium intake to maintain whole body sodium homeostasis. In addition, ENaC is inhibited by high levels of intracellular Na(+) [Na(+)](i), presumably to prevent cell Na(+) overload and swelling. However, it is not clear if this regulation is relevant in vivo. We show here that in rats, an acute (4 h) oral sodium load decreases whole-cel...

The amount of dietary sodium intake regulates the renin angiotensin system (RAS) and blood pressure, both of which play critical roles in atherosclerosis. However, there are conflicting findings regarding the effects of dietary sodium intake on atherosclerosis. This study applied a broad range of dietary sodium concentrations to determine the concomitant effects of dietary sodium intake on the ...

The transmembrane sodium gradient is essential for both excitability of the cardiac cell and the regulation of the cytoplasmic concentrations of Ca and protons. In addition, movements of Na across the mitochondrial membrane affect matrix protons and calcium. In the first part of the review, we discuss the most important pathways responsible for sarcolemmal and mitochondrial sodium movements. Th...

Measurements were made of the sodium outflux rate constant, (o)k(Na), and sodium influx rate constant, (i)k(Na), at varying concentrations of extracellular (Na(o)) and intracellular (Na(c)) sodium. (o)k(Na) increases with increasing [Na(o)] in the presence of extracellular potassium (K(o)) and in solutions containing ouabain. In K-free solutions which do not contain ouabain, (o)k(Na) falls as [...

The present study was designed to investigate the role of abnormalities in red blood cell sodium-potassium-chloride (Na-K-Cl) cotransport and Na+ pump as predictors of the pressor response to chronic oral Na+ loading in young whites and blacks. Subjects were healthy adults from 18 to 23 years of age and included normotensive whites (n = 24) and normotensive blacks (n = 35). Red blood cell trans...

The ubiquitously expressed serum and glucocorticoid regulated kinase 1 (SGK1) is tightly regulated by osmotic and hormonal signals, including glucocorticoids and mineralocorticoids. Recently, SGK1 has been implicated as a signal hub for the regulation of sodium transport. SGK1 modulates the activities of multiple ion channels and carriers, such as epithelial sodium channel (ENaC), voltage-gated...

We present evidence that Na-K-ATPase in the rat proximal tubule is directly activated by ANG II much faster than previously observed. Specifically, we show that a 2-min exposure to 0.1 and 1 nM ANG II slowed the rate of intracellular sodium accumulation in response to an increase in extracellular sodium added in the presence of gramicidin D. From these data, we show that ANG II directly stimula...

BACKGROUND The local anesthetic lidocaine affects neuronal excitability in the central nervous system; however, the mechanisms of such action remain unclear. The intracellular sodium concentration ([Na]i) and sodium currents (INa) are related to membrane potential and excitability. Using an identifiable respiratory pacemaker neuron from Lymnaea stagnalis, the authors sought to determine whether...

Renal Na-K-ATPase activity changes adaptively in response to chronic alterations in sodium reabsorption or potassium secretion, but the role of this enzyme in rapid adjustments of renal tubular Na and K transport is not known. To evaluate this question, microsomal Na-K-ATPase specific activity and kinetics were determined in the rat and guinea pig kidney after massive but short-term (3 h) sodiu...

Sodium movement across the luminal membrane of the toad bladder is the rate-limiting step for active transepithelial transport. Recent studies suggest that changes in intracellular sodium regulate the Na permeability of the luminal border, either directly or indirectly via increases in cell calcium induced by the high intracellular sodium. To test these proposals, we measured Na movement across...