Figure 1.

Discrete multicellular model of endothelial tube. Idealized diamond-shaped ECs, each with length = 35 μm (L_cell), width = 8.6 μm (d_cell), and thickness d, are arranged into a cylinder (dashed lines) with N_circum (= 14) cells encompassing the circumferential direction (y) and 71 cells encompassing the axial direction (x). Under control conditions, each EC is coupled to its four immediate neighbors through gap junctions. The total number of ECs in the discrete model of an endothelial tube of length L = 2.5 mm and diameter D = 38 μm is 1988. Each EC is modeled as described in Silva et al.¹⁷ and contains: store-operated Ca²⁺channels (SOC); nonselective cation channels (NSC); volume regulated anion channels (VRAC); Ca²⁺-activated Cl⁻ channels (CaCC); small- and intermediate-conductance Ca²⁺-activated K⁺ channels (SK_Ca and IK_Ca); Na⁺-K⁺-ATPase (NaK); plasma membrane Ca²⁺-ATPase (PMCA); Na⁺/Ca²⁺ exchanger (NCX); Na⁺/K⁺/Cl⁻ cotransporter (NaKCl); sarcoplasmic endoplasmic reticulum Ca²⁺-ATPase (SERCA); and IP₃ receptors (IP₃R). The electrical equivalent diagram of a rectangular region (dashed red line), which incorporates four halves of ECs and four gap junctions is shown (bottom right). Each EC has a total membrane resistance R_m, each EC-EC coupling has resistance R_gj, and there are N_circum such rectangular regions in the circumferential direction. The effective membrane and axial resistivities of the endothelial tube can be derived from N_circum parallel units having membrane resistance of R_m/2 and axial resistance of R_gj over distance L_cell.