Variation of intracellular Ca2+ following Ca2+ current in heart. A theoretical study of ionic diffusion inside a cylindrical cell.
The variation in the concentration of a diffusing substance inside a cylindrical cell submitted to a time-dependent flux at the sarcolemmal membrane was studied theoretically. An application was derived to estimate the local modifications of intracellular free Ca2+ concentration ([CA2+]i) induced by the slow inward Ca2+ current (ICa) in frog heart. During a O mV voltage clamp depolarization, [Ca2+]i at the inner side of the membrane rises earlier and faster than [Ca2+]i at the center of the cell. The binding of intracellular Ca2+ to specific sites enhances the deviation between the two concentrations and may generate an accumulation-depletion process of Ca2+ near the membrane. However, it also decreases the overall [Ca2+]i. The relatively slow diffusion of sarcoplasmic Ca2+ does not significantly affect the kinetics of ICa through a modification in the Ca2+ gradient across the membrane.
D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D006321:Heart / Q000187:drug effects / Q000502:physiology*; D008433:Mathematics; D008564:Membrane Potentials / Q000187:drug effects; D008954:Models, Biological; D009206:Myocardium / Q000378:metabolism*; D011898:Ranidae; D012508:Sarcolemma / Q000502:physiology
D002118:Calcium