[Transient currents and Ca2+ gradient relaxation in characean algae cells: theory and experiment].
Transient Ca2+ and Ca2+-dependent Cl- currents of plasmatic membranes of voltage-clamped Chara corallina freshwater alga cells were studied. Our earlier described method was used for rapid (approximately 10 ms) injection of Ca2+ ions into the cell during the deactivation period of calcium channels following their activation by a positive voltage pulse (injection by "tail" Ca2+ current). This procedure allowed one to determine the amplitude of the Ca2+ component, as well as the amplitude and kinetics of the submembrane Ca2+ concentration-dependent Cl- component for the transient current. Calculations based on the cell model allowing for Ca2+ diffusion, the Ca2+-buffering properties of the cytoplasm, and the nonlinear dependency of iCl on [Ca2+]cyt, as well as the presence of chloroplasts agreed well with the experimentally observed behavior of the transient current. The slow stage of the [Ca2+]cyt relaxation to the resting level (approximately 10(-7) M), related to the functioning of Ca2+-ATPases, was shown to take approximately 10(2) s. We assume this stage to determine the duration of the refractory period after the generation of action potential.
Berestovskiĭ
G N
GN
Kataev
A A
AA
Tsyganov
M A
MA
D000200:Action Potentials; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism / Q000502:physiology*; D044784:Chara / Q000378:metabolism / Q000502:physiology* / Q000648:ultrastructure; D002736:Chloroplasts / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism
D015220:Calcium Channels; D000252:Calcium-Transporting ATPases; D002118:Calcium