Mathematical Model of the Calcium-Dependent Chloride Current in a Smooth Muscle Cell

摘要

Employing the Hodgkin-Huxley formalism, we have developed a mathematical model of the calciumdependent chloride current on the basis of published experimental data concerning the kinetics of such current in cells of different types. The obtained results are destined for further use in a currently developed model of a smooth muscle cell of the bladder detrusor. A feature of the simulated current is the presence of two components with common kinetics of calcium-dependent activation and different (fast and slow) kinetics of voltage-dependent activation. In computational experiments performed with the use of a protocol of stepwise clamp of the membrane potential or the intracellular calcium concentration ([Са2+]i), static and dynamic dependences of the current on the membrane potential and [Са2+]i (the current-voltage and current-concentration relations, IVs and ICs, respectively) were obtained; analogous dependences of the kinetic variables of calcium- and voltage-dependent activation of the current were also plotted. The obtained characteristics of the simulated current were close to those of the prototype currents. The following properties were typical of the current: (i) the outward rectification, (ii) enhancement of the rectification effect with increase in the [Са2+]i, and (iii) a higher sensitivity to [Са2+]i deviations from the basal level (manifested in greater ratios of the current/concentration increments) within the range <1 μM, as compared to that within the range of higher concentrations.