Fig 2: Insulin secretion by isolated pancreatic islets in response to GLP-1 agonists and an antagonist.(A) Insulin secretion was concentration-dependent with GLP-1 (7–37), and was higher in the presence of a DPPIV inhibitor. The basal insulin secretion (at 2.75 mM glucose) in the absence of GLP-1 is shown by the dashed line. (B) The synthetic GLP-1 analogue exendin-4 did not stimulate an insulin response from the isolated equine pancreatic islets. (C) The insulin release stimulated by GLP-1 (at the estimated EC50 of 1 nM) tended to be lower (27%, P = 0.08) in the presence of the antagonist exendin 9-39 (1 nM).

Fig 3: GLP-1 secretion by equine intestinal explants in response to glucose.The mean (±s.e.m.) GLP-1 concentration reached following the incubation of intestinal explants for 30 min in the presence of two glucose concentrations. GLP-1 secretion tended to be greater (P = 0.07) when the explants were stimulated with 4 mM glucose, compared to 12 mM glucose. The data were individually corrected for the incidental secretion when the explant was incubated without glucose.