Effect Of Pancreastatin Research Articles

Effect of pancreastatin on cerulein-stimulated pancreatic blood flow and exocrine secretion in anaesthetized rats.

Pancreastatin (PST) is an inhibitor of pancreatic exocrine secretion in vivo but not in vitro, which suggests that the inhibitory effect of PST is indirect, that is, not mediated by a specific receptor on pancreatic acinar cells. In this study, we investigated the effects of PST on pancreatic exocrine secretion and local pancreatic blood flow in anaesthetized rats to elucidate the participation of PST in indirect regulation of pancreatic exocrine function through blood supply. Pancreastatin (100, 200 or 500 pmol/kg per h) was administered intravenously under background infusion of cerulein (0.5 microg/kg per h), a cholecystokinin analogue. Pancreatic exocrine secretion was monitored by volume and protein output of the pancreatic juice and local pancreatic blood flow was measured by the hydrogen gas clearance method. Pancreastatin significantly reduced cerulein-induced local pancreatic blood flow in a dose-dependent manner. Pancreatic exocrine secretion was also reduced significantly by PST dose-dependently. Pancreastatin did not change systemic blood pressure. These results suggested that the reduction of pancreatic blood flow is associated with the reduction of pancreatic exocrine secretion. We conclude that the mechanism of PST-induced inhibition of pancreatic exocrine secretion is, at least, partly mediated by the reduction of local pancreatic blood flow through blockade, caused by the action of cerulein on pancreatic blood flow.

Effects of pancreastatin and somatostatin on secretagogues-induced rise in intracellular free calcium in single rat pancreatic islet cells

Pancreastatin (PST) is known to inhibit glucose-stimulated insulin release both in vivo and in vitro, but it has not been determined whether PST acts directly on pancreatic B-cells and no study has been reported on the effect of PST on the intracellular free Ca 2+ concentration ([Ca 2+] i) in pancreatic islet cells. In the present study, by using the dissociated rat pancreatic B-cells, we examined the effects of PST on the increase in [Ca 2+] i induced by several insulin secretagogues, and compared them with those of somatostatin (SRIF). PST (1–100 nM) dose-dependently inhibited the glucose-induced rise in [Ca 2+] i in single pancreatic islet cells. SRIF (10 nM) also suppressed the glucose-induced rise in [Ca 2+] i. These demonstrated direct inhibitory actions of PST and SRIF on the pancreatic B-cells. Acetylcholine (ACh, 10 μM) with 5.5 mM glucose induced a biphasic increase in [Ca 2+] i in single islet cells. SRIF (10 nM) suppressed the second phase in [Ca 2+] i increase without affecting the first phase. In contrast, PST (100 nM) had no effect on the ACh-induced response. Gastric inhibitory polypeptide (100 nM) with 5.5 mM glucose induced a rise in [Ca 2+] i in single islet cells. SRIF inhibited this increase, but PST did not. Both PST and SRIF failed to affect the sustained rise in [Ca 2+] i evoked by excess K +. These results suggest that PST and SRIF suppress the glucose-induced insulin secretion at least partly by inhibiting the rise in [Ca 2+] i in pancreatic B-cells. Furthermore, PST may suppress the glucose-induced rise in [Ca 2+] i via a mechanism different from that of SRIF.

Pancreastatin activates pertussis toxin-sensitive guanylate cyclase and pertussis toxin-insensitive phospholipase C in rat liver membranes

We have recently found the calcium dependent glycogenolytic effect of a pancreastatin on rat hepatocytes and the mobilization of intracellular calcium. To further investigate the mechanism of action of pancreastatin on liver we have studied its effect on guanylate cyclase, adenylate cyclase, and phospholipase C, and we have explored the possible involvement of GTP binding proteins by measuring GTPase activity as well as the effect of pertussis toxin treatment of plasma liver membranes on the pancreastatin stimulated GTPase activity and the production of cyclic GMP and myo-inositol 1,4,5-triphosphate. Pancreastatin stimulated GTPase activity of rat liver membranes about 25% over basal. The concentration dependency curve showed that maximal stimulation was achieved at 10(-7)M pancreastatin (EC50 = 3 nM). This stimulation was partially inhibited by treatment of the membranes with pertussis toxin. The effect of pancreastatin on guanylate cyclase and phospholipase C were examined by measuring the production of cyclic GMP and myo-inositol 1,4,5-triphosphate respectively. Pancreastatin increased the basal activity of guanylate cyclase to a maximum of 2.5-fold the unstimulated activity at 30 degrees C, in a time- and dose-dependent manner, reaching the maximal stimulation above control with 10(-7) M pancreastatin at 10 min (EC50 = 0.6 nM). This effect was completely abolished when rat liver membranes had been ADP-ribosylated with pertussis toxin. On the other hand, adenylate cyclase activity was not affected by pancreastatin. Phospholipase C activity of rat liver membranes was rapidly stimulated (within 2-5 min) at 30 degrees C by 10(-7) M pancreastatin, reaching a maximum at 15 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Pancreastatin increases free cytosolic Ca2+ in rat hepatocytes, involving both pertussis-toxin-sensitive and -insensitive mechanisms.

Freshly isolated rat hepatocytes, loaded with the Ca2+ probe Fluo-3, responded to homologous pancreastatin with a sudden increase in free cytosolic Ca2+ ([Ca2+]i) as well as glucose release. Addition of rat pancreastatin (0.1 microM) to hepatocytes resulted in an increase in [Ca2+]i from 150 nM to 700 nM, which declined back to nearly basal values within 2-3 min. Half-maximal and maximal effects were observed at 0.3 and 100 nM pancreastatin respectively. The increase in [Ca2+]i induced by vasopressin and noradrenaline was very similar in extent (from 150 to 800 nM) to that produced by pancreastatin. Neither the alpha 1-adrenergic blocker prazosin nor the vasopressin antagonist V1 modified the increase in [Ca2+]i induced by pancreastatin. Pig pancreastatin and its 33-49 C-terminal fragment produced about 65 and 75% of the effect of homologous pancreastatin respectively. Glucose production correlated with changes in [Ca2+]i in the same order of potency: vasopressin > rat pancreastatin > pig 33-49 pancreastatin > pig 1-49 pancreastatin. The effect of pancreastatin on [Ca2+]i was decreased by 50% when Ca2+ was omitted from the medium, and totally abolished when hepatocytes were depleted of internal Ca2+ stores by preincubation without Ca2+ and with 2 mM EGTA. When hepatocytes were preincubated for 5 min with PMA, the effects of ATP and noradrenaline were prevented, and those of vasopressin and pancreastatin remained unchanged. The pretreatment of hepatocytes with pertussis toxin diminished the response to pancreastatin and vasopressin. These results suggest that pancreastatin is a new Ca(2+)-mobilizing glycogenolytic hormone acting through a specific receptor which may involve both pertussis-toxin-sensitive and -insensitive GTP-binding regulatory proteins.

Effects of Pancreastatin (24–49) on Growth of Normal Pancreas and Pancreatic Cancer

In the present study, the effects of pancreastatin on growth are evaluated in two human pancreatic cancer cell lines, in vivo and in vitro, and on athymic nude mouse pancreas. SW-1990 and MIA PaCa-2 pancreatic cancer cell lines were grown in serum-supplemented and serum-free medium in the presence of pancreastatin (10(-11)-10(-6) M), or cholecystokinin (CCK) (10(-11)-10(-8) M) or combinations thereof. Growth was evaluated by [3H]thymidine incorporation and cell counts. Pancreastatin significantly inhibited DNA synthesis in both cell lines, and cell counts in SW-1990 on days 3 and 5 but not 7. CCK-stimulated cell growth was inhibited in both cell lines and mouse pancreas by pancreastatin. Pancreastatin had no effect in the presence of fetal bovine serum. In the in vivo experiments, pancreastatin (15 micrograms/kg) did not affect growth of SW-1990 xenografts to nude mice, but inhibited CCK-stimulated growth transiently. Pancreastatin (100 micrograms/kg) transiently decreased volumes of MIA PaCa-2 xenografts to nude mice and significantly decreased weight, protein, and DNA of mouse pancreas. Fasting glucose levels of mice treated with pancreastatin 100 micrograms/kg for 35 days were significantly lower than controls. Our results demonstrate that pancreastatin not only inhibits CCK-stimulated pancreatic growth but also has inhibitory effects by itself.

Effects of pancreastatin and chromogranin A on insulin release stimulated by various insulinotropic agents

The effects of porcine pancreastatin on insulin release stimulated by insulinotropic agents, glucagon, cholecystokinin-octapeptide (CCK-8), gastric inhibitory polypeptide (GIP) and l-arginine, were compared to those of bovine chromogranin A (CGA) using the isolated perfused rat pancreas. Pancreastatin significantly potentiated glucagon-stimulated insulin release (first phase: 12.5 ± 0.9 ng/8 min ; second phase: 34.5 ± 1.6 ng/25 min in controls; 16.5 ± 1.1 ng/8 min and 44.0 ± 2.2 ng/25 min in pancreastatin group), whereas CGA was ineffective. The first phase of l-arginine-stimulated insulin release was also potentiated by pancreastatin ( 6.9 ± 0.5 ng/5 min in controls, 8.4 ± 0.6 ng/5 min in pancreastatin group), but not by CGA. Pancreastatin did not affect CCK-8 or GIP-stimulated insulin release. Similarly, CGA did not affect insulin release stimulated by CCK-8 or GIP. These findings suggest that pancreastatin stimulates insulin release in the presence of glucagon. Because pancreastatin can have multiple effects on insulin release, which are dependent upon the local concentration of insulin effectors, pancreastatin may participate in the fine tuning of insulin release from B cells.

Long Term Inhibitory Effects of Pancreastatin and Diazepam Binding Inhibitor on Pancreatic β-Cell Deoxyribonucleic Acid Replication, Polyamine Content, and Insulin Secretion*

The two peptides pancreastatin and diazepam binding inhibitor (DBI) were recently demonstrated in pancreatic islets and were shown to inhibit insulin secretion in short term experiments. In the present study we investigated long term effects of pancreastatin and DBI on the DNA synthesis, polyamine content, and insulin secretion of pancreatic beta-cells in tissue culture. For this purpose fetal rat pancreatic islets enriched in beta-cells were isolated and cultured for 3 days at different concentrations of rat pancreastatin and porcine DBI. It was found that pancreastatin dose-dependently decreased beta-cell DNA synthesis, reaching maximal inhibition at 100 nM. In parallel with this, pancreastatin also decreased insulin secretion and the islet contents of insulin and the polyamines spermidine and spermine. These effects were abolished by a high glucose concentration or addition of GH. Also, DBI evoked a dose-dependent inhibition of beta-cell DNA synthesis but affected neither the islet contents of insulin or polyamines nor insulin secretion. Like pancreastatin, DBI was ineffective in preventing the increased beta-cell DNA synthesis, insulin content, or secretion in response to high glucose or GH. It is concluded that pancreastatin and DBI inhibit beta-cell DNA synthesis and function in vitro. In the case of pancreastatin these inhibitory effects may be mediated by a decrease in islet polyamine content. It is suggested that pancreastatin and DBI may influence beta-cell replication and function in vivo in an autocrine or paracrine fashion.

Effects of synthetic human pancreastatin on pancreatic secretion and blood flow in rats and dogs

Effects of synthetic human pancreastatin-52 and human pancreastatin-29 on pancreatic secretion and blood flow were examined in rats and dogs. Synthetic human pancreastatin-52 and human pancreastatin-29 were equally potent in suppressing the release of amylase stimulated by cholecystokinin in rats in vivo. However, neither human pancreastatin-52 nor human pancreastatin-29 altered basal and cholecystokinin-stimulated amylase release from isolated dispersed rat pancreatic acini. In studies in dogs, human pancreastatin-29 suppressed releases of amylase and protein stimulated by cholecystokinin, but did not alter pancreatic blood flow. These results suggest that the inhibitory effects of pancreastatin on pancreatic secretion do not involve a direct action on pancreatic acinar cells nor alteration of pancreatic blood flow. Pancreastatin probably is important in regulating exocrine pancreatic secretions as well as endocrine pancreatic secretions.

The Effect of Pancreastatin on Endocrine and Exocrine Pancreas

The Effect of Pancreastatin on Endocrine and Exocrine Pancreas

Effects of Pancreastatin on Pancreatic Hormone Secretion in the Dog

In the anaesthetized dog, porcine pancreastatin (98 pmol/min) was infused for 10 min into the pancreaticoduodenal artery either alone or during infusion of glucose. Blood was sampled from the pancreaticoduodenal vein. We found that pancreastatin inhibited pancreatic insulin output only under normoglycaemic conditions. Furthermore, pancreastatin significantly stimulated pancreatic glucagon and somatostatin outputs both during normo- and hyperglycaemic conditions. Our results show that pancreastatin has the capability to affect directly the three pancreatic hormone secretions in dogs.

Pancreastatin: A novel peptide inhibitor of parietal cell signal transduction

The direct inhibition of secretion by pancreastatin was investigated in rabbit isolated parietal cells. Pancreastatin exerted no influence on basal aminopyrine uptake. Pancreastatin inhibited histamine stimulated aminopyrine uptake through a decrease in intracellular cAMP. Pancreastatin inhibition of histamine stimulated uptake was blocked in the presence of pertussis toxin. Pancreastatin also inhibited the carbachol stimulated increase in aminopyrine accumulation. However, the effects of pancreastatin on carbachol stimulation were not reversed by pertussis toxin. Pancreastatin did not alter the carbachol induced increase in cytosolic free calcium. Thus, pancreastatin appears to inhibit parietal cell signal transduction at multiple points along the second messenger pathways.

Pancreastatin inhibits insulin secretion as induced by glucagon, vasoactive intestinal peptide, gastric inhibitory peptide, and 8-cholecystokinin in the perfused rat pancreas

Pancreastatin is a 49-amino acid straight chain molecule isolated from porcine pancreatic extracts. In the perfused rat pancreas, this peptide has been shown to inhibit unstimulated insulin release and the insulin responses to glucose, arginine, and tolbutamide. To further explore the influence of pancreastatin on islet cell secretion, the effect of synthetic porcine pancreastatin (a 2-μg priming dose, followed by constant infusion at a concentration of 15.7 nmol/L) was studied on the insulin, glucagon, and somatostatin responses to 1 nmol/L vasoactive intestinal peptide (VIP), 1 nmol/L gastric inhibitory peptide (GIP), and 1 nmol/L 26 to 33 octapeptide form of cholecystokinin (8-CCK). The effect of pancreastatin on the insulin and somatostatin secretion elicited by glucagon (20 nmol/L) was also examined. Pancreastatin infusion consistently reduced the insulin responses to VIP, GIP, and 8-CCK without modifying glucagon or somatostatin release. It also inhibited the insulin release but not the somatostatin output induced by glucagon. These observations broaden the spectrum of pancreastatin as an inhibitor of insulin release. The finding that pancreastatin does not alter glucagon or somatostatin secretion supports the concept that it influences the B cell directly, and not through an A cell or D cell paracrine effect.

Effect of Pancreastatin on Pancreatic Endocrine and Exocrine Secretion

Pancreastatin is a novel peptide that was recently purified from extracts of the porcine pancreas. The present study shows that pancreastatin (10(-9)-10(-8) M) can stimulate release of insulin from both the isolated perfused rat pancreas and from cultured rat islet cells in the presence of a low, non-insulinotropic concentration of glucose (4.2 mM). Pancreastatin (10(-9) M) can also inhibit release of insulin stimulated by a high concentration of glucose (16.7 mM). Pancreastatin, at 10(-8) M, can enhance glucose (8.3 mM) induced release of insulin in the static islet cell incubation. In addition, pancreastatin (10(-9)-10(-8) M) can inhibit, in a dose-dependent fashion, cholecystokinin (CCK)-8 stimulated release of amylase from dispersed guinea pig pancreatic acini. Pancreastatin alone, however, did not affect basal release of amylase. Our study shows that pancreastatin can exert a direct effect on both pancreatic endocrine and exocrine secretion.

Effect of pancreastatin on pancreatic exocrine secretion in vivo and in vitro

Effect of pancreastatin on pancreatic exocrine secretion in vivo and in vitro

Effects of pancreastatin on insulin and pancreatic polypeptide secretion in the dog.

Porcine pancreastatin (1.19 nmol) was administered into the peripheral vein (i.v.) or the third cerebral ventricle (i.t.v.) of dogs and its effect on the secretion of insulin and pancreatic polypeptide (PP) studied. Neither means of administration had any effect on basal and glucose-induced insulin or PP secretion. However, i.v. pancreastatin did inhibit the i.v. CCK-8-induced insulin but not PP release. Pancreastatin may thus play a role in the regulation of insulin secretion in the canine pancreas.

Effects of systemic pancreastatin on memory retention.

Pancreastatin, a peptide isolated from the pancreas, was shown to enhance memory retention after peripheral administration in mice when administration following T-maze footshock avoidance training. The effect of pancreastatin on memory retention, one week after training, was time dependent showing enhancement of retention when pancreastatin was administered 0 and 30 min but not 60 min after training. Pancreastatin reversed the amnesia produced by scopolamine. The pancreastatin fragment (33-49) also enhanced memory. Pancreastatin did not increase glucose in vivo. We conclude that peripherally administered pancreastatin modulates memory processing.

Effects of pancreastatin on insulin, glucagon and somatostatin secretion by the perfused rat pancreas

Pancreastatin is a novel peptide, isolated from porcine pancreatic extracts, which has been shown to inhibit glucose-induced insulin release “in vitro”. To achieve further insight into the influence of pancreastatin on pancreatic hormone secretion, we have studied the effects of this peptide on unstimulated insulin, glucagon and somatostatin output, as well as on the responses of these hormones to glucose and to tolbutamide in the perfused rat pancreas. Pancreastatin strongly inhibited unstimulated insulin release as well as the insulin responses to glucose and to tolbutamide. It did not significantly affect glucagon or somatostatin output under any of the above-mentioned conditions. These findings suggest that pancreastatin inhibits B-cell secretory activity directly, and not through an A-cell or D-cell paracrine effect.

Pancreastatin and islet hormone release.

The effect of pancreastatin on the release of insulin, glucagon, and somatostatin was studied in the isolated perfused rat pancreas. After an initial equilibration period (-20 to 0 min) with a basal glucose concentration (3.3 mM), the pancreata were perfused with either 16.7 mM glucose (0-40 min) or with 20 mM arginine (0-20 min). Pancreastatin was introduced 10 min prior to and throughout the administration of the high glucose and arginine and continued during their perfusion. As expected, the glucose and the arginine augmented insulin and somatostatin release. Pancreastatin (1 and 10 nM) markedly suppressed the first phase of insulin release with both insulinogogues used, while the early somatostatin secretion was not significantly decreased. However, the peak incremental somatostatin response to arginine was reduced by 50% (P less than 0.05). Conversely, the peptide (10 nM) tended to augment arginine-induced glucagon release. Pancreastatin (100 nM) also suppressed glucose-stimulated insulin release from isolated rat islets. These pancreastatin-mediated alterations in islet hormone release are reminiscent of those known to characterize non-insulin-dependent diabetes. Therefore, the significance of pancreastatin in islet physiology and pathophysiology deserves special consideration.