Smith G D
Institute of Theoretical Dynamics, University of California, Davis 95616, USA.
Biophys J. 1996 Dec;71(6):3064-72. doi: 10.1016/S0006-3495(96)79500-0.
We derive an analytical steady-state solution for the Ca2+ profile near an open Ca2+ channel based on a transport equation which describes the buffered diffusion of Ca2+ in the presence of rapid stationary and mobile Ca2+ buffers (Wagner and Keizer, 1994). This steady-state rapid buffering approximation gives an upper bound on local Ca2+ elevations such as Ca2+ puffs or sparks when conditions for the validity of the rapid buffering approximation are met and is an alternative to approximations that assume that mobile buffers are unsaturable. This result also provides an analytical estimate of the cytosolic Ca2+ domain concentration ([Ca2+]d) near a channel pore and shows the dependence of [Ca2+]d on moderate concentrations of endogenous mobile buffer, Ca2+ indicator dye, and bulk cytosolic Ca2+. Assuming a simple relationship between [Ca2+]d and the lumenal depletion domain of an intracellular Ca2+ channel, lumenal and cytosolic Ca2+ profiles are matched to give an implicit analytical expression for the effect of bulk lumenal Ca2+ on [Ca2+]d.
基于一个描述在快速固定和移动钙缓冲剂存在下钙离子缓冲扩散的输运方程（瓦格纳和凯泽，1994年），我们推导了开放钙离子通道附近钙离子分布的解析稳态解。当满足快速缓冲近似有效性的条件时，这种稳态快速缓冲近似给出了局部钙离子升高（如钙离子瞬变或火花）的上限，并且是假设移动缓冲剂不饱和的近似方法的替代方法。该结果还提供了通道孔附近胞质钙离子域浓度（[Ca2+]d）的解析估计，并显示了[Ca2+]d对内源性移动缓冲剂、钙离子指示剂染料和胞质钙离子中等浓度的依赖性。假设[Ca2+]d与细胞内钙离子通道的腔耗竭域之间存在简单关系，将腔和胞质钙离子分布相匹配，以给出关于腔钙离子总量对[Ca2+]d影响的隐式解析表达式。
