Fig. 2: The stomach produced active GLP-1 in response to a gastric glucose load.

Spontaneous (a) and IBMX-stimulated (b) GLP-1 release from fundus, antrum, and colon fragments ex vivo. Stomach and colon from overnight fasted lean rat were collected and incubated for 1 h with PBS (without IBMX) and with 100 µM IBMX. GLP-1 was assayed in the supernatant. Results are expressed as mean ± SEM in pmoles/mg protein for basal release in a with n = 12 for fundus and n = 14 for antrum and the colon and statistically analyzed with one-way ANOVA followed by Tukey’s multiple comparison test. ***P < 0.001, **P < 0.01, and NS not significant. When stimulated with IBMX, results are expressed as mean ± SEM in percentage of basal release (without IBMX n = 19 for fundus, n = 15 for antrum, and n = 13 antrum and with IBMX n = 11 for fundus, antrum, and colon) and statistical analysis was performed using Mann–Whitney test to compared with and without IBMX **P < 0.01, ***P < 0.001. c Scheme of the stomach showing the portal and gastric vein blood sampling and loading of PBS and glucose. d In vivo intragastric load of glucose increases total GLP-1 levels in the portal vein of anesthetized rat. Total GLP-1 levels after intragastric (Ig) or intraduodenal (IDuo) load of glucose (2 g/kg BW) or PBS measured in the portal vein (blue: Ig Glc and PBS; green: IDuo Glc). Data are the mean ± SEM of n values indicated at each time point on the graph. Data were analyzed by a two-way ANOVA. *P < 0.05 vs. PBS. Total (e) and active (f) GLP-1 levels increase after intragastric load of glucose in the gastric vein of anesthetized rat. Total and active GLP-1 levels after an intragastric (Ig) load of glucose (2 g/kg BW) or PBS measured in the gastric vein. Data are the mean ± SEM, n values indicated at each time point on the graph, and data were analyzed by a two-way ANOVA. *P < 0.05 vs. PBS. Source data are provided as a Source data file.