Tuyển tập các báo cáo nghiên cứu về y học được đăng trên tạp chí y học quốc tế cung cấp cho các bạn kiến thức về ngành y đề tài: Donnan effect on chloride ion distribution as a determinant of body fluid composition that allows action potentials to spread via fast sodium channels. | Kurbel Theoretical Biology and Medical Modelling 2011 8 16 http content 8 1 16 THEORETICAL BIOLOGY AND MEDICAL MODELLING REVIEW Open Access Donnan effect on chloride ion distribution as a determinant of body fluid composition that allows action potentials to spread via fast sodium channels Sven Kurbel Correspondence sven@ Dept. of Physiology Osijek Medical Faculty Osijek Croatia 2 BioMed Central Abstract Proteins in any solution with a pH value that differs from their isoelectric point exert both an electric Donnan effect DE and colloid osmotic pressure. While the former alters the distribution of ions the latter forces water diffusion. In cells with highly CP-permeable membranes the resting potential is more dependent on the cytoplasmic pH value which alters the Donnan effect of cell proteins than on the current action of Na K pumps. Any weak positive or negative electric disturbances of their resting potential are quickly corrected by chloride shifts. In many excitable cells the spreading of action potentials is mediated through fast voltage-gated sodium channels. Tissue cells share similar concentrations of cytoplasmic proteins and almost the same exposure to the interstitial fluid IF chloride concentration. The consequence is that similar intra- and extra-cellular chloride concentrations make these cells share the same Nernst value for Cl-. Further extrapolation indicates that cells with the same chloride Nernst value and high chloride permeability should have similar resting membrane potentials more negative than -80 mV. Fast sodium channels require potassium levels 20 times higher inside the cell than around it while the concentration of Cl- ions needs to be 20 times higher outside the cell. When osmotic forces electroneutrality and other ions are all taken into account the overall osmolarity needs to be near 280 to 300 mosm L to reach the required resting potential in excitable cells. High plasma protein concentrations keep the IF .
