Fig. 4.

Insulin secretion from islets isolated from normal and GLP-1 receptor knockout mice. (a) Islets from CD1 wild-type mice. After a preperifusion the concentration of glucose was 3 mM from 0–60 min and 10 mM after 60 min. At 10 min, 100, and 1,000 nM compound 2, 100 nM GLP-1 or glucose alone was added and removed again at 70 min. Data are shown as mean ± SEM for three groups of 30 islets. Asterisks indicate a significant difference between GLP-1 and the 1,000 nM compound 2 vs. glucose alone. (b) Islets from CD1 GLP-1 receptor knockout mice. After the preperifusion, the concentration of glucose was 3 mM from 0 to 30 min and 10 mM after 30 min. At 10 min, 1,000 nM compound 2 and 100 nM GLP-1, 10 μM imidazoline control compound NNC77-0074, or vehicle were added and removed again at 60 min. Groups of islets were perifused the day after isolation. Before perifusate collection was started, all groups of islets were perifused with 3 mM glucose for 30 min to establish stable basal rates of release. Data are shown as mean ± SEM for three groups of 30 islets. Asterisks indicate a significant difference between imidazoline vs. all other groups.