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Inhibition of stimulated exocrine pancreatic secretion by leptin
April 2000
AGAA299
1663
1665
INHIBITION OF STIMULATED EXOCRINE PANCREATIC SECRETION BY LEPTIN. Jan Bilski, Aleksandra Szlachcic, Jolanta Jaworek, Joanna Bonior, Jolanta Majka, Artur Dembinski, Zygmunt Warzecha, Stanislaw J. Konturek, Dept of Physiology, Jagiellonian Univ Med Sch, Cracow, Poland; Dept Physiol , Univ Med Sch, Cracow, Poland. Leptin is an adipocyte produced peptide that controls food intake and the energy expenditure. Many of its effects are mediated centrally via hypothalamic receptor but also peripheral effects of leptin such as gastroprotection has been recently described and found to contribute to action of CCK on the stomach. Leptin receptors and leptin were detected recently in the. pancreas. CCK was found to increase the plasma leptin but this leptin seems to originate mainly from stomach where it inhibits gastric secretion but its role control of pancreatic secretion has not been studied. The aim of this study was to evaluate the effect of leptin on pancreatic secretion in vivo in rats surgically with pancreatic fistulas and in vitro using dispersed pancreatic acini on exocrine. After preliminary administration of various doses ofleptin, the standard dose of (10 I-tglkg-h, s.c.), that inhibited gastric secretion for testing pancreatic secretion. The pancreatic secretory response to sham feeding, ordinary feeding and pancreatic juice diversion were significantly inhibited by this dose of leptin by about 29%, 60% and 82%, respectively. In isolated pancreatic acini, obtained from the rat by collagenase digestion, increasing concentrations of leptin (10·1~-1O.7M) added to incubation medium failed to affect significantly basal secretion but produced dose-dependent inhibition of amylase release stimulated by submaximal dose of caerulein (1O_ 12M) but not by urecholine (lO·5M). We conclude that leptin inhibits stimulated pancreatic secretion both in vivo and in vitro, and this effect could be mediated at least in part by its direct action on pancreatic acinar cells
INTESTINAL LYMPH FISTULA RAT: A MODEL FOR STUDYING THE RELEASE OF GLUCAGON-LIKE PEPTIDE 1. David D' Alessio, Jeffrey B. Schwimmer, Min Liu, Patrick Tso, Univ of Cincinnati Coli of Medicine, Cincinnati, OH; Acad Hosp Med Ctr, Cincinnati, OH.
1664 UROGUANYLIN AND SEROTONIN SECRETION FROM THE ISOLATED RAT JEJUNUM: VASCULAR AND LUMINAL RELEASE. Jean Claustre, Pascale Plaisancie, Severine Pain, Gerard Jourdan, JeanAlain Chayvialle, Jean-Claude Cuber, INSERM U45, Lyon, France. Background and aims: Uroguanylin (URO) is a peptide recently isolated from the mucosa of the small bowel. This peptide has been proposed both to induce intestinal secretion through activation of luminal receptors on enterocytes and to be a natriuretic hormone. The rates of secretion of URO in the intestinal lumen and in the portal vein have not been determined yet. Because URO has been proposed to be colocalized with serotonin in enterochromaffin cells of the proximal gut, we addressed the portal and luminal secretions of URO and serotonin from rat jejunum in basal conditions and under stimulation. Methods: The secretions of URO and serotonin were measured in the portal vein and luminal effluents of a model of isolated rat jejunum (15 ern). The jejunum was vascularly perfused with an oxygenated medium (Krebs-Henseleit buffer containing dextran, glucose, albumin and aminoacids). The lumen was perfused with isotonic saline. Experiments consisted in a 10 min basal period followed by a 30 min stimulation. URO was assayed by RIA with an antiserum that crossreacts less than I% with the other intestinal peptide, guanylin. Serotonin was assayed by HPLC with electrochemical detection. Results: The jejunum URO content was 2.6±0.3 pmoles/g tissue. When purified on HPLC, the immunoreactive material isolated from luminal and portal fluids collected from the jejunum was eluted in one peak, corresponding to synthetic rat URO. In control conditions, URO was secreted both in the luminal and portal effluents from the jejunum (secretion rates: 94±32 and 51 ±9 fmoles/min, respectively). Serotonin, in contrast was secreted mainly in the portal effluent (14± I pmoles/min), and to a minor extent in the luminal effluent (2.8±0.2 pmoles/min). Carbachol (10-4 M) strongly stimulated portal URO secretion, to 280% of controls, whilst isoproterenol had no significant effect (177% of controls). Portal serotonin secretion was increased both by carbachol and isoproterenol, to ISOand 200% of controls, respectively. None of the stimulants increased significantly luminal URO or serotonin secretion but isoproterenol decreased luminal uro secretion, to 60% of controls. Conclusions: URO is secreted both in the lumen and the portal vein, thus suggesting potential luminal and endocrine effects. Serotonin in contrast would act preferentialy through the vascular way. The patterns of secretion of the two mediators in control conditions and under stimulation suggest that their secretion could be regulated specifically.
Background. Glucagon-like peptide I (GLP-l) is derived from differential post-translational processing of proglucagon (proG) by endocrine cells in the intestinal mucosa. GLP-I is secreted following carbohydrate, fat, or mixed meals and serves as an incretin hormone augmenting nutrient stimulated insulin secretion. The in vivo study of GLP-I secretion is limited by the peptide's low circulating concentrations and its rapid metabolism to an inactive form. Aim. We will test the hypothesis that GLP-I is detectable in intestinal lymph, and that this compartment will be a useful site to study GLP-I secretion. Methods. Under halothane anesthesia, the small intestinal lymph duct was cannulated with a PVC tube. A silastic tube was installed in the duodenum for infusion. Glucose-saline was infused at 3 m1Ih during the recovery period (overnight), and the animals were kept at an ambient temperature of 30° C. Lymph was collected from the major intestinal lymph duct of unanesthetized rats receiving intraduodenal (ID) infusions of 10% glucose (n=6) or intralipid (n=3) and from the jugular vein of animals receiving an ID glucose meal (n=6). Plasma was extracted with ethanol, lymph with diisopropyl ether, and GLP-I levels determined by RIA. Results. In those animals fed glucose, basal (fasting) levels of GLP-I were significantly greater in lymph (54±4 pglrnl) than in plasma (10±2 pg/ml; p <0.05). Peak GLP-Ilevels during the ID infusion of glucose were 249±99 pg/ml in lymph, and 44±7 pg/rnl in plasma (p<0.05). ID intralipid caused lymph concentrations of GLP-I· to increase from fasting values of87±3 to peak values of 160±3. Degradation ofGLP-I, measured as the recovery of intact, iodinated GLP-I, was substantially less in buffer and lymph than plasma (92,84, and 17 % respectively). Conclusions. We demonstrated that GLP-I is present in lymph at higher concentrations than plasma, and that feeding glucose or lipid increases the secretion of GLP-I into lymph. Furthermore, the degradation of lymphatic GLP-I is relatively minimal. Based on these findings we propose that measurement of GLP-I in the lymph collected from conscious intestinal lymph fistula rats will be a useful model for studying the secretion of this peptide.
1666 INHIBITION OF CENTRAL TRH-INDUCED GASTRIC ACID SECRETION BY INTRAVENOUS (IV) SECRETIN IS MEDIATED BY SOMATOSTATIN RECEPTOR 2. Ming-Luen Doong, Hong Yang, Pu-Qing Yuan, Travis Solomon, Yvette F. Tache, John H. Walsh, Ctr for Gen Education, National Yang-Ming Univ, Taipei, Taiwan, ROC; Cure/Ddrc., UCLA, Los Angeles, CA. Background: Secretin is reported to inhibit gastrin-induced acid secretion through vagal afferent sensory nerves and local release of somatostatin (SST). Aim: To investigate whether peripheral secretin I)inhibits acid response to central vagal stimulation; 2)induces Fos expression in medullary dorsal vagal complex (DMN + NTS) and area postrema (AP); 3) inhibits acid secretion through SST receptor 2. Methods: Male SD rats fasted for 24 h were anesthetized with urethane. Gastric acid secretion was induced by intracisternal injection (ic) of the TRH analog, RX 77368 and measured by flushing the stomach through gastric cannula. Fos expression in the medulla was quantitated by immunohistochemistry at 90 min after intraperitoneal (ip) secretin injection in awake rats. Results: ic RX 77368 (5ng) stimulated net gastric acid output (p,ffioV90 min) to 56.8±8.0. Secretin (0.25,0.5 and I nmol/kg-h by iv infusion started 10 min before ic RX 77368) reduced acid output to 37.3±12.7, 11.1±1O.5 and -3.7±3.9 respectively. Pretreatment with the SST receptor 2 antagonist, PRL-2903 (1.3JLmoVkg, iv), not only abolished the inhibitory effects of secretin but also augmented both basal and ic RX 77368-induced acid secretion (244.5±39.0). Pretreatment with saline (vehicel for PRL-2903) did not alter the stimulatory effect of ic RX 77368 (42.7±8.7) or the inhibitory effect ofiv secretin (-11.0±2.3 at I nmoVkg-h). Secretin (1 nmol/kg-h) did not inhibit iv PRL-2903 (1.3JLmoVkg)-induced increase in basal acid secretion (143.3±25.7). Secretin (1 nmoVkg, ip) did not increase significantly the number of Fos positive neurons in the medial and interstitial NTS, DMN and AP (Table). Conclusions: I) secretin inhibits ic TRHinduced gastric acid secretion through SST receptor 2; 2) secretin ip at the dose of I nmol/kg does not induce Fos expression in medullary dorsal vagal complex and the area postrema.
Secretin (1 nmollkg,ip) did not increase Fos induction inthe medullary dorsal vagal complex and the area postrema (number ofFos positive neurons/nuclei, mean of20sections)
Group saline secretin
NTS
DMN
AP
18.4±2.0 21.0±2.9
4.9±1.4 5.1±2.0
19.0±3.6 30.0±11.8
AGAA299
1663
1665
INHIBITION OF STIMULATED EXOCRINE PANCREATIC SECRETION BY LEPTIN. Jan Bilski, Aleksandra Szlachcic, Jolanta Jaworek, Joanna Bonior, Jolanta Majka, Artur Dembinski, Zygmunt Warzecha, Stanislaw J. Konturek, Dept of Physiology, Jagiellonian Univ Med Sch, Cracow, Poland; Dept Physiol , Univ Med Sch, Cracow, Poland. Leptin is an adipocyte produced peptide that controls food intake and the energy expenditure. Many of its effects are mediated centrally via hypothalamic receptor but also peripheral effects of leptin such as gastroprotection has been recently described and found to contribute to action of CCK on the stomach. Leptin receptors and leptin were detected recently in the. pancreas. CCK was found to increase the plasma leptin but this leptin seems to originate mainly from stomach where it inhibits gastric secretion but its role control of pancreatic secretion has not been studied. The aim of this study was to evaluate the effect of leptin on pancreatic secretion in vivo in rats surgically with pancreatic fistulas and in vitro using dispersed pancreatic acini on exocrine. After preliminary administration of various doses ofleptin, the standard dose of (10 I-tglkg-h, s.c.), that inhibited gastric secretion for testing pancreatic secretion. The pancreatic secretory response to sham feeding, ordinary feeding and pancreatic juice diversion were significantly inhibited by this dose of leptin by about 29%, 60% and 82%, respectively. In isolated pancreatic acini, obtained from the rat by collagenase digestion, increasing concentrations of leptin (10·1~-1O.7M) added to incubation medium failed to affect significantly basal secretion but produced dose-dependent inhibition of amylase release stimulated by submaximal dose of caerulein (1O_ 12M) but not by urecholine (lO·5M). We conclude that leptin inhibits stimulated pancreatic secretion both in vivo and in vitro, and this effect could be mediated at least in part by its direct action on pancreatic acinar cells
INTESTINAL LYMPH FISTULA RAT: A MODEL FOR STUDYING THE RELEASE OF GLUCAGON-LIKE PEPTIDE 1. David D' Alessio, Jeffrey B. Schwimmer, Min Liu, Patrick Tso, Univ of Cincinnati Coli of Medicine, Cincinnati, OH; Acad Hosp Med Ctr, Cincinnati, OH.
1664 UROGUANYLIN AND SEROTONIN SECRETION FROM THE ISOLATED RAT JEJUNUM: VASCULAR AND LUMINAL RELEASE. Jean Claustre, Pascale Plaisancie, Severine Pain, Gerard Jourdan, JeanAlain Chayvialle, Jean-Claude Cuber, INSERM U45, Lyon, France. Background and aims: Uroguanylin (URO) is a peptide recently isolated from the mucosa of the small bowel. This peptide has been proposed both to induce intestinal secretion through activation of luminal receptors on enterocytes and to be a natriuretic hormone. The rates of secretion of URO in the intestinal lumen and in the portal vein have not been determined yet. Because URO has been proposed to be colocalized with serotonin in enterochromaffin cells of the proximal gut, we addressed the portal and luminal secretions of URO and serotonin from rat jejunum in basal conditions and under stimulation. Methods: The secretions of URO and serotonin were measured in the portal vein and luminal effluents of a model of isolated rat jejunum (15 ern). The jejunum was vascularly perfused with an oxygenated medium (Krebs-Henseleit buffer containing dextran, glucose, albumin and aminoacids). The lumen was perfused with isotonic saline. Experiments consisted in a 10 min basal period followed by a 30 min stimulation. URO was assayed by RIA with an antiserum that crossreacts less than I% with the other intestinal peptide, guanylin. Serotonin was assayed by HPLC with electrochemical detection. Results: The jejunum URO content was 2.6±0.3 pmoles/g tissue. When purified on HPLC, the immunoreactive material isolated from luminal and portal fluids collected from the jejunum was eluted in one peak, corresponding to synthetic rat URO. In control conditions, URO was secreted both in the luminal and portal effluents from the jejunum (secretion rates: 94±32 and 51 ±9 fmoles/min, respectively). Serotonin, in contrast was secreted mainly in the portal effluent (14± I pmoles/min), and to a minor extent in the luminal effluent (2.8±0.2 pmoles/min). Carbachol (10-4 M) strongly stimulated portal URO secretion, to 280% of controls, whilst isoproterenol had no significant effect (177% of controls). Portal serotonin secretion was increased both by carbachol and isoproterenol, to ISOand 200% of controls, respectively. None of the stimulants increased significantly luminal URO or serotonin secretion but isoproterenol decreased luminal uro secretion, to 60% of controls. Conclusions: URO is secreted both in the lumen and the portal vein, thus suggesting potential luminal and endocrine effects. Serotonin in contrast would act preferentialy through the vascular way. The patterns of secretion of the two mediators in control conditions and under stimulation suggest that their secretion could be regulated specifically.
Background. Glucagon-like peptide I (GLP-l) is derived from differential post-translational processing of proglucagon (proG) by endocrine cells in the intestinal mucosa. GLP-I is secreted following carbohydrate, fat, or mixed meals and serves as an incretin hormone augmenting nutrient stimulated insulin secretion. The in vivo study of GLP-I secretion is limited by the peptide's low circulating concentrations and its rapid metabolism to an inactive form. Aim. We will test the hypothesis that GLP-I is detectable in intestinal lymph, and that this compartment will be a useful site to study GLP-I secretion. Methods. Under halothane anesthesia, the small intestinal lymph duct was cannulated with a PVC tube. A silastic tube was installed in the duodenum for infusion. Glucose-saline was infused at 3 m1Ih during the recovery period (overnight), and the animals were kept at an ambient temperature of 30° C. Lymph was collected from the major intestinal lymph duct of unanesthetized rats receiving intraduodenal (ID) infusions of 10% glucose (n=6) or intralipid (n=3) and from the jugular vein of animals receiving an ID glucose meal (n=6). Plasma was extracted with ethanol, lymph with diisopropyl ether, and GLP-I levels determined by RIA. Results. In those animals fed glucose, basal (fasting) levels of GLP-I were significantly greater in lymph (54±4 pglrnl) than in plasma (10±2 pg/ml; p <0.05). Peak GLP-Ilevels during the ID infusion of glucose were 249±99 pg/ml in lymph, and 44±7 pg/rnl in plasma (p<0.05). ID intralipid caused lymph concentrations of GLP-I· to increase from fasting values of87±3 to peak values of 160±3. Degradation ofGLP-I, measured as the recovery of intact, iodinated GLP-I, was substantially less in buffer and lymph than plasma (92,84, and 17 % respectively). Conclusions. We demonstrated that GLP-I is present in lymph at higher concentrations than plasma, and that feeding glucose or lipid increases the secretion of GLP-I into lymph. Furthermore, the degradation of lymphatic GLP-I is relatively minimal. Based on these findings we propose that measurement of GLP-I in the lymph collected from conscious intestinal lymph fistula rats will be a useful model for studying the secretion of this peptide.
1666 INHIBITION OF CENTRAL TRH-INDUCED GASTRIC ACID SECRETION BY INTRAVENOUS (IV) SECRETIN IS MEDIATED BY SOMATOSTATIN RECEPTOR 2. Ming-Luen Doong, Hong Yang, Pu-Qing Yuan, Travis Solomon, Yvette F. Tache, John H. Walsh, Ctr for Gen Education, National Yang-Ming Univ, Taipei, Taiwan, ROC; Cure/Ddrc., UCLA, Los Angeles, CA. Background: Secretin is reported to inhibit gastrin-induced acid secretion through vagal afferent sensory nerves and local release of somatostatin (SST). Aim: To investigate whether peripheral secretin I)inhibits acid response to central vagal stimulation; 2)induces Fos expression in medullary dorsal vagal complex (DMN + NTS) and area postrema (AP); 3) inhibits acid secretion through SST receptor 2. Methods: Male SD rats fasted for 24 h were anesthetized with urethane. Gastric acid secretion was induced by intracisternal injection (ic) of the TRH analog, RX 77368 and measured by flushing the stomach through gastric cannula. Fos expression in the medulla was quantitated by immunohistochemistry at 90 min after intraperitoneal (ip) secretin injection in awake rats. Results: ic RX 77368 (5ng) stimulated net gastric acid output (p,ffioV90 min) to 56.8±8.0. Secretin (0.25,0.5 and I nmol/kg-h by iv infusion started 10 min before ic RX 77368) reduced acid output to 37.3±12.7, 11.1±1O.5 and -3.7±3.9 respectively. Pretreatment with the SST receptor 2 antagonist, PRL-2903 (1.3JLmoVkg, iv), not only abolished the inhibitory effects of secretin but also augmented both basal and ic RX 77368-induced acid secretion (244.5±39.0). Pretreatment with saline (vehicel for PRL-2903) did not alter the stimulatory effect of ic RX 77368 (42.7±8.7) or the inhibitory effect ofiv secretin (-11.0±2.3 at I nmoVkg-h). Secretin (1 nmol/kg-h) did not inhibit iv PRL-2903 (1.3JLmoVkg)-induced increase in basal acid secretion (143.3±25.7). Secretin (1 nmoVkg, ip) did not increase significantly the number of Fos positive neurons in the medial and interstitial NTS, DMN and AP (Table). Conclusions: I) secretin inhibits ic TRHinduced gastric acid secretion through SST receptor 2; 2) secretin ip at the dose of I nmol/kg does not induce Fos expression in medullary dorsal vagal complex and the area postrema.
Secretin (1 nmollkg,ip) did not increase Fos induction inthe medullary dorsal vagal complex and the area postrema (number ofFos positive neurons/nuclei, mean of20sections)
Group saline secretin
NTS
DMN
AP
18.4±2.0 21.0±2.9
4.9±1.4 5.1±2.0
19.0±3.6 30.0±11.8