Transient currents and Ca2+ gradient relaxation in characean algae cells: Theory and experiment

Autor: Tsyganov Ma, Berestovskiĭ Gn, Kataev Aa
Rok vydání: 2006
Předmět:
Zdroj: Biophysics. 51:873-881
ISSN: 1555-6654
0006-3509
DOI: 10.1134/s0006350906060042
Popis: The transient Ca2+ and Ca2+-dependent Cl− currents in the plasma membrane of voltage-clamped cells of the freshwater alga Chara corallina were studied. We used our own earlier proposed method, which utilized a rapid (∼10 ms) injection of Ca2+ ions into the cell during the deactivation period of calcium channels after their activation with a positive voltage pulse (injection with a “tail” Ca2+ current). This procedure makes it possible to determine the amplitude of the Ca2+ component in the transient current as well as the amplitude and kinetics of the Cl− component, dependent on the Ca2+ submembrane concentration. The calculated results, which used a cell model that takes the diffusion of Ca2+, the Ca2+-buffering properties of the cytoplasm, and the nonlinear dependence of i Cl on [Ca2+]cyt, as well as the presence of chloroplasts into account, were in good agreement with the actual behavior of transient current in the experiments. It was demonstrated that the duration of the slow stage of [Ca2+]cyt relaxation to the resting level (∼10−7 M) (which is related to the function of Ca2+-ATPases), was ∼102 s. This suggests that the slow stage determines the duration of the refractory period after generation of the action potential.
Databáze: OpenAIRE
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