Sodium extracellular

Sodium chloride [7647-14-5] is an essential dietary component. It is necessary for proper acid—base balance and for electrolyte transfer between the iatra-and extracellular spaces. The adult human requirement for NaCl probably ranges between 5—8 g/d. The normal diet provides something ia excess of 10 g/d NaCl, and adding salt duting cooking or at the table iacreases this iatake. 

Sodium and Potassium. Whereas sodium ion is the most abundant cation in the extracellular fluid, potassium ion is the most abundant in the intracellular fluid. Small amounts of K" are requited in the extracellular fluid to maintain normal muscle activity. Some sodium ion is also present in intracellular fluid (see Fig. 5). Common food sources rich in potassium may be found in Table 7. Those rich in sodium are Hsted in Table 8. 

Active Transport. Maintenance of the appropriate concentrations of K" and Na" in the intra- and extracellular fluids involves active transport, ie, a process requiring energy (53). Sodium ion in the extracellular fluid (0.136—0.145 AfNa" ) diffuses passively and continuously into the intracellular fluid (<0.01 M Na" ) and must be removed. This sodium ion is pumped from the intracellular to the extracellular fluid, while K" is pumped from the extracellular (ca 0.004 M K" ) to the intracellular fluid (ca 0.14 M K" ) (53—55). The energy for these processes is provided by hydrolysis of adenosine triphosphate (ATP) and requires the enzyme Na" -K" ATPase, a membrane-bound enzyme which is widely distributed in the body. In some cells, eg, brain and kidney, 60—70 wt % of the ATP is used to maintain the required Na" -K" distribution. 

The volume of extracellular fluid is direcdy related to the Na" concentration which is closely controlled by the kidneys. Homeostatic control of Na" concentration depends on the hormone aldosterone. The kidney secretes a proteolytic enzyme, rennin, which is essential in the first of a series of reactions leading to aldosterone. In response to a decrease in plasma volume and Na" concentration, the secretion of rennin stimulates the production of aldosterone resulting in increased sodium retention and increased volume of extracellular fluid (51,55). 

A surgical implant is constantly bathed in extracellular tissue fluid. Basically water, this fluid contains electrolytes, complex compounds, oxygen and carbon dioxide. Electrolytes present in the largest amounts are sodium (Na ) and chloride (Cl ) ions. Most of the fluids existing in the body (such as blood, plasma and lymph) have a chloride content (and pH) somewhat similar to that of sea water (about 5 to 20g/l and pH about 8) . 

Diuretics promote the urinary excretion of sodium and water by inhibiting the absorption of filtered fluid across the renal tubular epithelium. The ensuing reduction in Na reabsorption reduces the Na content of the body, the critical determinant of extracellular and plasma fluid volumes. Thus, the use of diuretics is primarily indicated in the treatment of edematous diseases and of arterial hypertension. 

Hyperaldosteronism is a syndrome caused by excessive secretion of aldosterone. It is characterized by renal loss of potassium. Sodium reabsorption in the kidney is increased and accompanied by an increase in extracellular fluid. Clinically, an increased blood pressure (hypertension) is observed. Primary hyperaldosteronism is caused by aldosterone-producing, benign adrenal tumors (Conn s syndrome). Secondary hyperaldosteronism is caused by activation of the renin-angiotensin-aldosterone system. Various dtugs, in particular diuretics, cause or exaggerate secondary peadosteronism. 

Neurotransmitter transporters determine the neurotransmitter concentration in the interstitium. High-affinity transporters can efficiently remove neurotransmitter from the extracellular space because cellular uptake is typically coupled to the translocation of sodium ions. 

The 3 subunits ((31 -(34) are membrane proteins with a single transmembrane domain and an extracellular immunoglobulin-like motif, and perform the regulatory roles of the sodium channel. The (31 subunit accelerates the activation and inactivation kinetics. The (32 subunit is covalently linked to the a subunit, and is necessary for the efficient assembly of the channel. The more recently identified (33 subunit is homologous to (31, but differs in its distribution within the brain and in a weaker accelerating property. The (34 subunit is similar to (32 and is covalently linked to the a subunit. 

Figure 8. Sensitivity of the FMLP-induced calcium signal to hyperosmolality. Indo-l-loaded neutrophils were stimulated with 10 M FMLP in a medium of high osmolality (645 mosmol/kg by addition of sodium HEPES), and indo-1 fluorescence was recorded as described in Figure 6. Trace 1 Cells in a medium with normal calcium and osmolality (reproduced from Figure 7). Trace 2 EGTA added to chelate extracellular calcium before stimulation extracellular calcium (1.5 miV) readded 70 s after stimulation. Trace 3 Cells in a medium with normal calcium (1.5 mW) EGTA added 70 s after stimulation to chelate extracellular calcium.

Hyaluronic acid is a linear polysaccharide found in the highest concentrations in soft connective tissues where it fills an important structural role in the organization of the extracellular matrix (23,24). It has been used in ophthalmic preparations to enhance ocular absorption of timolol, a beta blocker used for the treatment of glaucoma (25), and in a viscoelastic tear formulation for conjunctivitis (26). The covalent binding of adriamycin and daunomycin to sodium hy-aluronate to produce water-soluble conjugates was recently reported (27). 

Involved in membrane function principal cations of extracellular-and intracellular fluids, respectively Sodium, potassium... 

The saxitoxins function by binding to a site on the extracellular surface of the voltage-activated sodium channel, interrupting the passive inward flux of sodium ions that would normally occur through the channel while it is in a conducting... 

Figure 1. Effect of 1% (w/v) pectin (pect), 1% galactose (gal), and of the simultaneous presence of 2% glucose (glu) on the production of extracellular polygalacturonase activity. Two-stages cultures were prepared as described under methods. Polygalacturonase was assayed in the culture filtrate as reducing sugar-releasing activity using sodium polypectate as a substrate.

Sodium, Na(I) has a normal concentration in human serum of 136-145 mmol/L (Tohda 1994) and makes up about 90 % of the cations present. (Many extracellular body fluids possess ranges from 7 mmol/L [mature milk] via 33 [saliva] to 145 mmol/ L [bile]). The reference method for determination is potentiometry with ion-selective electrodes (PISE). 

The ventricular action potential is depicted in Fig. 6-2.2 Myocyte resting membrane potential is usually -70 to -90 mV, due to the action of the sodium-potassium adenosine triphosphatase (ATPase) pump, which maintains relatively high extracellular sodium concentrations and relatively low extracellular potassium concentrations. During each action potential cycle, the potential of the membrane increases to a threshold potential, usually -60 to -80 mV. When the membrane potential reaches this threshold, the fast sodium channels open, allowing sodium ions to rapidly enter the cell. This rapid influx of positive ions... 

The most common therapeutic maneuver to decrease the incidence of contrast-induced nephropathy is extracellular volume expansion.36 Several recent studies have compared the efficacy of isotonic sodium chloride (0.9%) to half normal... 

Patients with acute hyperkalemia usually require other therapies to manage hyperkalemia until dialysis can be initiated. Patients who present with cardiac abnormalities caused by hyperkalemia should receive calcium gluconate or chloride (1 g intravenously) to reverse the cardiac effects. Temporary measures can be employed to shift extracellular potassium into the intracellular compartment to stabilize cellular membrane effects of excessive serum potassium levels. Such measures include the use of regular insulin (5 to 10 units intravenously) and dextrose (5% to 50% intravenously), or nebulized albuterol (10 to 20 mg). Sodium bicarbonate should not be used to shift extracellular potassium intracellularly in patients with CKD unless severe metabolic acidosis (pH less than 7.2) is present. These measures will decrease serum potassium levels within 30 to 60 minutes after treatment, but potassium must still be removed from the body. Shifting potassium to the intracellular compartment, however, decreases potassium removal by dialysis. Often, multiple dialysis sessions are required to remove potassium that is redistributed from the intracellular space back into the serum. 

The extracellular fluid (ECF) is the fluid outside the cell and is rich in sodium, chloride, and bicarbonate. O The ECF is approximately one-third of TBW (14 L in a 70-kg man or 12 Lin a 70-kg woman) and is subdivided into two compartments the interstitial fluid and the intravascular fluid. The interstitial fluid (also known as lymphatic fluid) represents the fluid occupying the spaces between cells, and is about 25% of TBW (10.5 L in a 70-kg man or 8.8 L in a 70-kg woman). The intravascular fluid (also known as plasma) represents the fluid within the blood vessels and is about 8% of TBW (3.4 L in a 70-kg man or 2.8 L in a 70-kg woman). The ECF is approximately one-third of TBW or 14 L in a 70-kg male. Because the exact percentages are cumbersome to recall, many clinicians accept that the ECF represents roughly 20% of body weight (regardless of gender) with 15% in the interstitial space and 5% in the intravascular space.6 Note that serum electrolytes are routinely measured from the ECF. 

The mainstay of treatment for established SOS is supportive care aimed at sodium restriction, increasing intravascular volume, decreasing extracellular fluid accumulation, and minimizing factors that contribute to or exacerbate hepatotoxicity and encephalopathy. Defibrotide has shown promising results in the treatment of SOS.44... 

Sodium is the most abundant extracellular cation in the body and is the major osmotically active ion in the extracellular fluid. Sodium concentration determines the distribution of... 

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