Pancreatic polypeptie (PP) is released from the pancreas in response to vagal stimulation. Amongst other effects, PP has been reported to inhibit pancreatic exocrine function. Apart from any potential physiological role, such inhibition could have important consequences for in vitro studies of pancreatic function employing acetylcholine as a stimulus. We have therefore tested the effect of bovine PP on two in vitro pancreatic preparations: the incubated, uncinate pancreas of young rats and the perfused cat pancreas. In the former, PP (10(-10)-10(-8)M) had little or no effect on enzyme discharge or45Ca efflux under basal conditions or during stimulation with caerulein, CCK-PZ or acetylcholine. In the perfused cat pancreas, similar concentrations of PP were also without effect on fluid secretion evoked by secretin infusion, or enzyme discharge evoked by CCK-PZ injection or infusion. We conclude that bovine PP has no direct effects on the cellular mechanisms responsible for pancreatic electrolyte secretion or enzyme discharge in the species studied.
Acetylcholine/pharmacology ; Amylases/secretion* ; Animal ; Caerulein/pharmacology ; Calcium/metabolism* ; Cats ; Cholecystokinin/pharmacology ; Electrolytes/secretion* ; In Vitro ; Pancreas/drug effects ; Pancreas/metabolism* ; Pancreatic Polypeptide/pharmacology* ; Perfusion ; Rats ; Secretin/pharmacology

OBJECTIVES: Investigate the influence of benazepril and amlodipine on the expression of secretin (PZ) and somatostatin (SS) in spontaneously hypertensive rats (SHR). METHODS: Forty-five SHRs (14 weeks old, male) were randomly assigned into 3 groups (=15):SHR group, Benazepril group (which was given benazepril 0.90 mg·kg·d) and Amlodipine group (SHRs were given amlodipine 0.45 mg· kg·d), taking WistarKyoto(WKY) as normal control (=15), meanwhile, rats in SHR group and WKY group were given the same volume of distilled water. After 8 weeks of intervention, the expression of protein and mRNA of PZ in duodenum and SS in sinuses ventriculi was detected by enzyme-linked immunoassay and RT-PCR. RESULTS: After 8 weeks of intervention, compared with the WKY group, the expression of protein and mRNA of PZ in duodenum and SS in sinuses ventriculi was increased significantly in SHR group (<0. 05). Compared with SHR group, the expression of PZ in duodenum and SS in sinuses ventriculi was decreased significantly in Benazepril group and Amlodipine group (<0.05). Compared with Benazepril group, in Amlodipine group the expression of PZ mRNA in duodenum and SS mRNA in sinuses ventriculi was decreased more significantly (<0.05). CONCLUSIONS The regulation disorder of PZ in duodenum and SS in sinuses ventriculi exists in SHR. The antihypertensive effect of benazepril and amlodipine may be realized by regulating the expression of PZ and SS, while the regulation of amlodipine is more obvious than benazepril.
Amlodipine ; pharmacology ; Animals ; Antihypertensive Agents ; pharmacology ; Benzazepines ; pharmacology ; Blood Pressure ; Hypertension ; drug therapy ; Male ; Random Allocation ; Rats ; Rats, Inbred SHR ; Rats, Inbred WKY ; Secretin ; metabolism ; Somatostatin ; metabolism

1. 5-HT inhibits spontaneous fluid secretion as well as stimulated secretion with secretin (cAMP mediated) or ACh (Ca2+ mediated) in the isolated guinea pig pancreatic ducts. 2. The inhibitory effect of 5-HT is reversible and is dependent on the concentration in the range 0.01-0.1 microM, which is much lower than those that affect intestinal motility and secretion. 3. The 5-HT3 receptor in duct cells appears to mediate the inhibitory effect of 5-HT. 4. [Ca2+]i is unlikely to mediate the inhibitory effect of 5-HT.
5-Methoxytryptamine/pharmacology ; Acetylcholine/pharmacology ; Animal ; Calcium/metabolism ; Guinea Pigs ; Pancreatic Ducts/metabolism* ; Pancreatic Ducts/drug effects ; Secretin/pharmacology ; Serotonin/pharmacology ; Serotonin/metabolism* ; Serotonin/analogs & derivatives* ; Vasodilator Agents/pharmacology

Since GABA and its related enzymes had been determined in beta-cells of pancreas islets, effects of GABA on pancreatic exocrine secretion were investigated in the isolated perfused rat pancreas. GABA, given intra-arterially at concentrations of 3, 10, 30 and 100 microM, did not exert any influence on spontaneous or secretin (12 pM)-induced pancreatic exocrine secretion. However, GABA further elevated cholecystokinin (10 pM)-, gastrin-releasing peptide (100 pM)- or electrical field stimulation-induced pancreatic secretions of fluid and amylase, dose-dependently. The GABA-enhanced CCK-induced pancreatic secretions were completely blocked by bicuculline (10 microM), a GABAA receptor antagonist but not affected by saclofen (10 microM), a GABA(B) receptor antagonist. The enhancing effects of GABA (30 microM) on CCK-induced pancreatic secretions were not changed by tetrodotoxin (1 microM) but partially reduced by cyclo-(7-aminoheptanonyl-Phe-D-Trp-Lys-Thr[BZL]) (10 microM), a somatostatin antagonist. In conclusion, GABA enhances pancreatic exocrine secretion induced by secretagogues, which stimulate enzyme secretion predominantly, via GABA(A) receptors in the rat pancreas. The enhancing effect of GABA is partially mediated by inhibition of islet somatostatin release. GABA does not modify the activity of intrapancreatic neurons.
Amylases/metabolism ; Animal ; Baclofen/pharmacology ; Baclofen/analogs & derivatives* ; Bicuculline/pharmacology ; Cholecystokinin/metabolism ; Dose-Response Relationship, Drug ; Electric Stimulation ; GABA/pharmacology* ; GABA Antagonists/pharmacology ; Gastrin-Releasing Peptide/metabolism ; Hormones/pharmacology ; In Vitro ; Pancreas/secretion* ; Pancreas/enzymology ; Pancreas/drug effects* ; Rats ; Receptors, GABA-A/metabolism ; Secretin/metabolism ; Somatostatin/pharmacology ; Tetrodotoxin/pharmacology

The gastrointestinal functions of secretin have been fairly well established. However, its function and mode of action within the nervous system remain largely unclear. To gain insight into this area, we have attempted to determine the effects of secretin on neuronal differentiation. Here, we report that secretin induces the generation of neurite outgrowth in pheochromocytoma PC12 cells. The expressions of Tau and beta-tubulin, neuronal differentiation markers, are increased upon secretin stimulation. In addition, secretin induces sustained mitogen-activated protein kinase (MAPK) activation and also stimulates the cAMP secretion. Moreover, the neurite outgrowth elicited by secretin is suppressed to a marked degree in the presence of either PD98059, a specific MAPK/ERK kinase (MEK) inhibitor, or H89, a specific protein kinase A (PKA) inhibitor. Taken together, these observations demonstrate that secretin induces neurite outgrowth of PC12 cells through cAMP-MAPK pathway, and provide a novel insight into the manner in which secretin participates in neuritogenesis.
Animals ; Cell Culture Techniques ; Cell Differentiation/drug effects ; Comparative Study ; Cyclic AMP/analysis/metabolism ; Enzyme-Linked Immunosorbent Assay ; Fluorescein-5-isothiocyanate ; Fluorescent Dyes ; Immunoblotting ; Immunohistochemistry ; Microscopy, Confocal ; Mitogen-Activated Protein Kinases/*metabolism ; Neurites/*drug effects ; Neurons/cytology/drug effects ; PC12 Cells ; Rats ; Research Support, Non-U.S. Gov't ; Reverse Transcriptase Polymerase Chain Reaction ; Secretin/*pharmacology