Figure 1.

A: Stimulus-secretion coupling of the pancreatic β-cell (“consensus model”). The arrows (↑,↓) indicate an increase or decrease of the indicated parameter. Glucose initiates insulin secretion following its metabolism with a resultant increase in cytoplasmic ATP-to-ADP ratio, closure of K_ATP channels, membrane depolarization, opening of voltage-gated Ca²⁺ channels, and initiation of Ca²⁺-dependent exocytosis of the insulin-containing secretory granules (SG). In addition, the β-cells are electrically coupled to neighboring β-cells via gap junctions consisting of connexin-36. Ψ, membrane potential. Sulfonylureas (SUs) stimulate insulin secretion by closing the K_ATP channels. B: Glucose-induced electrical activity recorded from a β-cell in intact mouse (top) or human (bottom) islets when the glucose concentration was increased from 1 to 10 or 11 mmol/L (as indicated by horizontal bars).