Effect of Ca²⁺ Efflux Pathway Distribution and Exogenous Ca²⁺ Buffers on Intracellular Ca²⁺ Dynamics in the Rat Ventricular Myocyte: A Simulation Study

Figure 7

Effect of EGTA and BAPTA on intracellular Ca²⁺ and 𝐼_Ca inactivation at the t-tubular and surface membranes during a voltage clamp pulse from −80 to 0 mV in the model. The upper panels show the differences between concentrations in the dyadic and subsarcolemmal spaces of the buffers with bound Ca²⁺  (Δ[B_ext−Ca²⁺]=[B_ext−Ca²⁺]_d−[B_ext−Ca²⁺]_s) and unbound Ca²⁺  (Δ[B_ext−free]=[B_ext−free]_d−[B_ext−free]_s). The other panels show Ca²⁺ transients in both dyadic spaces ([Ca²⁺]_dt,[Ca²⁺]_ds), Ca²⁺-dependent inactivation of t-tubular and surface membranes 𝐼_Ca (CDI_t, CDI_s), and time courses of related current components (𝐼_Ca,dt and 𝐼_Ca,ds). The solid, dashed, dotted, and dashed-dotted lines show the data obtained in control conditions and in the presence of 5 mM EGTA, 10 mM EGTA, and 10 mM BAPTA, respectively. The insets in the graphs of [Ca²⁺]_dt and [Ca²⁺]_ds show the dyadic Ca²⁺ transients in the presence of Ca²⁺ buffers at a higher gain.