FIGURE 2.

Models of calcium dynamics in SMCs. (a) The Wong and Klassen model of Ca²⁺ dynamics and membrane's electrical behavior in vascular smooth muscle (reproduced with permission from Ref 53. Copyright 1993 Elsevier). The model includes two intracellular stores. A-store is an IP₃-sensitive store. C-store is replenished by extracellular Ca²⁺. J_eff and J_D are the active and passive transmembrane Ca²⁺ efflux; J_p is the Ca²⁺ uptake rate of the A-store; I_Ca is the Ca²⁺ current through the voltage-operated channel; I_in is the inward current through the receptor-operated channel; I_K,Ca and I_K are the calcium and voltage-dependent K⁺ channels. (b) Minimal model reproduced from Parthimos and coworkers.⁵⁸ Model contains two independent internal stores [a ryanodine-sensitive (CICR) and inositol 1,4,5-trisphosphate (InsP3) sensitive]. Membrane component contains descriptions for: transmembrane currents for Cl^–, K⁺ channels; voltage- and receptor-operated Ca²⁺ channels (VOCCs and ROCCs, respectively); Na⁺-K⁺-ATPase, and Ca²⁺-ATPase pumps; NCX. (c) Detailed model reproduced with permission from Ref 62. Copyright 2003 Elsevier. Membrane model (upper panel) describing ionic membrane currents and transmembrane potential. Black and white indicates resistance with voltage-dependent nonlinearity, and the all white resistor indicates linear element. Fluid compartment model (lower panel) describes ionic dynamics, Ca²⁺ buffering, and Ca²⁺ handling by sarcoplasmic reticulum (SR). The SR is divided into a ryonadine-sensitive release compartment and an uptake compartment containing SERCA pumps that communicate. (d) Diagram of the cell model presented and reproduced from Ref 65. Copyright 2007 American Physiological Society. Model contains three intracellular compartments: bulk cytosol (cyt), microdomains (md), and sarcoplasmic reticulum (SR). J_i,diff is the electrodiffusive flux of ion i between the microdomains and the bulk cytosol.