.Physiomodel.Electrolytes

Information

Electrolytes have four main functions:

• Establish the osmotic concentration gradients on cell membranes
• With balanced concentrations together with acid-base buffers establish the optimal acidity.
• With balanced concentrations together with radicals and antioxidants establish the optimal reduction potential.
• Electric signaling of cells such as neural action potential is possible because of passive/active selective membrane transports of electrolytes.

The main electrolytes are:

• Sodium (Na+). Reabsorption of sodium in kidney nephrons is one of the main power for reabsorption of water [Wright1982,Bruun1990]. This process is driven by aldosterone[Young1976,Stanton1986] and angiotensin II [Ofangii1986,Lohmeier1998,Seeliger1999]. Sodium is reabsorbed in each part of nephron in different way such as from proximal tubule [Wiederholt1967,Gullans1985], from loop of Henle [Cortney1966] or from distal tubule[Morgan1969]. Other type of excretion is by sweating[Epstein1999,Quinton1991,Sato1989].
• Potassuim (K+). The main compartment for potassium is intracellular fluid. Excretion of potassium by nephrons is driven also by aldosterone feedback control [Young1976, Young1983, Young1988]. The amount of secreted potassium to urine is dependent also on potasium plasma concentration [Toussaint1962] and on sodium excretion [Good1984,Young1984]. Other type of excretion is by sweating[Epstein1999,Quinton1991,Sato1989].
• Chloride(Cl-) is the main plasma anion. His renal excretion such as renal excretion of amonium and bicarbonates is driven by the acidity of plasma [Cogan1979,Sartorius1949]. Other type of excretion is by sweating[Epstein1999,Quinton1991,Sato1989].
• Amonium(NH4+) is formed and excreted in kidney to compensate plasma hydrogen ions concentration[Rodriguez-Nichols1984], because its production consume the free hydrogen ions changing to a strong cation at pH<=7.4.
• Phosphates(H2PO4-, HPO4^2-) and sulphate(SO4^2-) has no renal reabsorption, which means, that their excretion to urine is dependent only on Donnan's equilibrium on glomerular membrane [Donnan1911].

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Copyright © 2008-2015 Marek Matejak, Charles University in Prague.