1. Enteric glucagon 37 rather than pancreatic glucagon 29 stimulates glucose absorption in rat intestine 
Frank Stümpel, Bettina Scholtka, Angela Hunger, Kurt Jungermann 
Gastroenterology 
Volume 115, Issue 5, Pages (November 1998)
DOI: /S (98)
Copyright © 1998 American Gastroenterological Association Terms and Conditions

2. Fig. 1
Scheme of the isolated perfused small intestine and the isolated perfused liver of the rat. (A) Nonrecirculating, vascular perfusion of the small intestine via the CT and SMA. Arrows indicate flow direction. Flow rates are expressed in milliliters per minute; flow in the SMA was measured by a flow meter and total flow by fractionated sampling of the outflow of the PV into calibrated tubes. The difference in flow between the two vessels was the calculated flow in the CT. Metabolite measurements were performed in the portal effluate. The effector substances were infused into the SMA. The carbohydrate bolus was applied via a catheter into the lumen of the duodenum. Outflow from the intestinal lumen was collected and analyzed for carbohydrates to determine transit time and volume of the intestinal effluate. (B) Perfusion of the isolated liver via the PV. Flow was determined by fractionated sampling of the IVC outflow, and metabolite measurements were performed in the effluate from the IVC. The effector substances were infused into the PV.
Gastroenterology  , DOI: ( /S (98) )
Copyright © 1998 American Gastroenterological Association Terms and Conditions

3. Fig. 2
Short-term increase by glucagon 37 (Gcg) 37 and dbcAMP but not glucagon 29 in glucose absorption in the isolated perfused small bowel of the rat. The intestine was perfused via the SMA and the CT with a Krebs–Henseleit bicarbonate buffer containing 5 mmol/L glucose, 2 mmol/L lactate, 0.2 mmol/L pyruvate, 3% dextran, and 1% bovine serum albumin equilibrated with 95% O2 and 5% CO2. Glucose (Glc) (1.65 mmol = 300 mg within 1 minute) was applied as an intraluminal bolus in the 6th minute and again in the 26th minute; it was absorbed as indicated by the increase in portal glucose concentration. From the 23rd to the 29th minute of the experiment, (A) glucagon 37 and (B) glucagon 29 (1 nmol/L each) and, from the 23rd to the 35th minute, (C) dbcAMP (10 μmol/L) or as a control buffer only (○) were infused into the mesenteric artery. Values are expressed as means ± SEM of 3–4 experiments each.
Gastroenterology  , DOI: ( /S (98) )
Copyright © 1998 American Gastroenterological Association Terms and Conditions

4. Fig. 3
Stimulation by glucagon (Gcg) 29 but not glucagon 37 of glucose release in the isolated perfused liver of the rat. The liver was perfused via the portal vein with a Krebs–Henseleit bicarbonate buffer containing 5 mmol/L glucose, 2 mmol/L lactate, 0.2 mmol/L pyruvate, and 0.5% bovine serum albumin. (A) Glucagon 37 or (B) glucagon 29 (1 nmol/L each) were infused via the portal vein from the 11th minute onwards for a period of 2 minutes. Values are expressed as means ± SEM of 3 experiments each.
Gastroenterology  , DOI: ( /S (98) )
Copyright © 1998 American Gastroenterological Association Terms and Conditions

5. Fig. 4
Reciprocal dose dependencies of the increases by glucagon (Gcg) 37 and glucagon 29 in the isolated perfused organs in intestinal glucose absorption and hepatic glucose release. The small intestine was perfused with luminal application of a 300-mg glucose bolus in the 6th and 26th minutes as described in the legend to Figure 1, and the liver was perfused as described in the legend to Figure 2. Glucagon 37 and glucagon 29 were infused with the indicated concentrations as described in Figures 1 and 2. Calculation of the area under the curve (AUC) for both kinds of experiments is described in Results. Values are expressed as means ± SEM of 3 experiments each.
Gastroenterology  , DOI: ( /S (98) )
Copyright © 1998 American Gastroenterological Association Terms and Conditions

6. Fig. 5
Dose dependency of the increase by glucagon 37 and glucagon 29 in [14C]3-O-methyl-glucose uptake in isolated enterocytes. Villus tips enterocytes were isolated by a collagenase-free chelate buffer and incubated in single glass flasks in a thermostated water bath (37°C). Glucagon 37 or glucagon 29 were given with the indicated concentrations 10 minutes before starting the experiments by adding 0.45 mmol/L [14C]3-O-methyl-glucose (0.6 μCi) into the flasks. Experiments were stopped with a rapid filtration technique, and the retained cell pellet was washed and counted for radioactivity. Data represent the means ± SEM of 6–10 experiments each.
Gastroenterology  , DOI: ( /S (98) )
Copyright © 1998 American Gastroenterological Association Terms and Conditions

7. Fig. 6
Increase by glucagon (Gcg) 37 and dbcAMP in intestinal glucose and galactose but not fructose absorption in the isolated perfused small intestine of the rat. The organ was perfused as described in the legend to Figure 1. Glucose, galactose, or fructose (1.65 mmol = 300 mg within 1 minute) was applied as an intraluminal bolus in the 6th minute and again in the 26th minute. Carbohydrate absorption was quantitated as described in Results. Glucagon 37 (1 nmol/L) was infused from the 23rd to the 29th minute, or dbcAMP (10 μmol/L) was infused from the 23rd to the 35th minute. (A) Basal carbohydrate absorption after the first luminal carbohydrate bolus without infusion of an effector. (B) Increase in carbohydrate absorption by glucagon 37. (C) Increase in carbohydrate absorption by dbcAMP after the second carbohydrate bolus. Values are expressed as means ± SEM of 3–4 experiments each.
Gastroenterology  , DOI: ( /S (98) )
Copyright © 1998 American Gastroenterological Association Terms and Conditions

8. Fig. 7
Increase by glucagon (Gcg) 37 via cAMP in glucose uptake via the SGLT1 in isolated rat enterocytes. Villus tip enterocytes were isolated by a collagenase-free chelate buffer and incubated in single glass flasks in a thermostated water bath (37°C). The experiments were started by adding 0.45 mmol/L [14C]3-O-glucose (0.6 μCi) into the flasks (A). In the controls, no effector was added, and [14C]3-O-methyl glucose uptake after 10 minutes was taken as 100% (actual transport rates are given in Results). dbcAMP (10 μmol/L); phlorizin, a specific SGLT1 inhibitor17 (1 mmol/L); (B) Rp-cAMPs, a specific cAMP antagonist18 (10 μmol/L); glucagon 37 (1 nmol/L); glucagon 37 plus Rp-cAMPS; and glucagon 37 plus phlorizin (Gcg-37 + phlorizin) were given 10 minutes before starting the experiments. The experiments were stopped at the indicated time points by quantitative transfer of the contents of the flasks onto a Whatman filter; the retained cell pellet was washed and counted for radioactivity. Data represent the means ± SEM of 4–5 experiments each.
Gastroenterology  , DOI: ( /S (98) )
Copyright © 1998 American Gastroenterological Association Terms and Conditions