Evaluating The Levels Of Some Selected Trace Metals, Renal Function Parameters And Liver Function Parameters Of Heavy Cosmetics Users Among Female Undergraduates And Compare Levels With Non-cosmetic Users

2.6.4.3    Body Electrolytes
Electrolytes are classified as either anions, negatively charged ions that move towards an anode, or cations, positively charged ions that move toward a cathode (Hogon and Wane, 2003). Physiological electrolytes include Na+, K+, Ca2+, Mg2+, Cl-, HCO3-, H2PO4-, SO42- and some organic anions, such as lactate. Although amino acids and proteins in solution also carry an electrical charge, they are usually considered separately from electrolytes. The major electrolytes (Na+, K+, Cl-, HCO3-) occur primarily as free ions, whereas significant amounts (>40%) of Ca2+, Mg2+ and trace elements are bound by proteins such as Albumin. Determination of body fluid concentration of the four major electrolytes (Na+, K+, HCO3-, Cl-) is commonly referred to as “electrolyte profile” (Mitchell et al., 2008).
2.6.4.4 Sodium
Sodium is the major cation of extracellular fluid. Because it represents approximately 90% of the 154 mmol of inorganic cations per liter of plasma, Na+ is responsible for almost one half the osmotic strength of plasma (Mitchell et al., 2008). It therefore has a central function in maintaining the normal distribution of water and the osmotic pressure in the extracellular fluid (ECF) compartment. The normal daily diet contains 8 to 15g (130 to 260mmol) of NaCl, which is nearly completely absorbed from the gastrointestinal tract (Vasuedevan et al., 2011). The body requires only 1 to 2 mmol/day, and the excess is excreted by the kidneys, which are the ultimate regulators of the amount of Na+ (and thus water) in the body (Elgart, 2004).
Sodium is freely filtered by the glomeruli. Seventy to eighty percent of the filtered Na+ load is then actively reabsorbed in the proximal tubules with Cl-, and water passively following in an iso-osmotic and electrically neutral manner. Another 20-25% is reabsorbed in the loop of Henle along with Cl- and more water. In the distal tubules, interaction of the adrenal hormone aldosterone with the coupled Na+ - K+ and Na+ - H+ exchange systems directly results in the reabsorption of Na+, and indirectly of Cl-, from the remaining 5% to 10% of the filtered load. It is the regulation of this latter fraction of filtered Na+ that primarily determines the amount of Na+ excreted in the urine (Chatterjea and Rana, 2012).
2.6.4.5    Potassium
Potassium is the major intracellular cation. In tissue cells, its average concentration is 150mmol/L, and in erythrocytes, the concentration is 105mmol/L (~23 times its concentration in the plasma) (Mitchell et al., 2008). High intracellular concentrations are maintained by the Na+, K+ ATPase pump, which is fuelled by oxidative energy and continually transports K+ into the cell against the concentration gradient. This pump is a critical factor in maintaining and adjusting the ionic gradients on which nerve impulses and contractility of muscle depend. Diffusion of K+ out of the cell into the plasma exceeds pump-mediated K+ uptake whenever pump activity is decreased (Annabel, 2000).
The body requirement for K+ is satisfied by a dietary intake of 50 to 150mmol/day. Potassium absorbed from the gastrointestinal tract is rapidly distribued, with a small amount taken up by cells and most excreted by the kidneys. Potassium filtered through the glomeruli is alsmost completely reabsorbed in the proximal tublues and is then secreted in the distal tubules in exchange for Na+ under the influence of aldosterone.