Fig. 6.

Somatostatin tonically inhibits both glucagon and insulin secretion. In Sst^+/+ islets (solid curved line), increasing glucose decreases glucagon secretion (A) while increasing somatostatin (B) and insulin secretion (C). Although insulin and glucagon are both higher in Sst^−/− islets (dashed curved line; A and C), glucose still retains its inhibitory effect on glucagon secretion (compare with the 4th figure in Ref. 15). Parameters are as follows for 1 mM glcuose (G1): ${\overline{\text{g}}}_{{\text{K}}_{\text{ATPa}}}$ = 3 nS, gK_ATPb = 150 pS, gK_ATPd = 0.29 nS, and k_SERCA = 0.05; for 7 mM glucose (G7): ${\overline{\text{g}}}_{{\text{K}}_{\text{ATPa}}}$ = 0.6 nS, gK_ATPb= 85 pS, gK_ATPd= 0.27 nS, k_SERCA = 0.5, and ${\overline{\text{g}}}_{\mathrm{S}\mathrm{O}\mathrm{C}}$ = 0.025 nS throughout. Relation of K_ATP conductance to bell-shaped curve is the same as in Fig. 5.