Fig. 12.

A and B: if glucagon is secreted from 5 uncoupled α-cells, total glucagon secretion is flat. Paracrine effects are suppressed by fixing ${\overline{\text{g}}}_{\mathrm{G}\mathrm{I}\mathrm{R}\mathrm{K}}$ to 0, r_−2a to 0.001, and ${\overline{\text{g}}}_{{\text{K}}_{\text{ATPa}}}$ to 2.7 nS. C and D: however, if the same cells are coupled by paracrine effects, total glucagon secretion is oscillatory. α-Cell heterogeneity was modeled by having different J_GK and κ values for the 5 α-cells: J_GK,a1 = 0.2, J_GK,a2 = 0.1, J_GK,a3 = 0.15, J_GK,a4 = 0.25, J_GK,a5 = 0.3, κ_a1 = 0.003, κ_a2 = 0.005, κ_a3 = 0.003, κ_a4 = 0.005, and κ_a5 = 0.003.