Stimulatory effects of human pancreatic polypeptide on rat pancreatic acini

The effect of human pancreatic polypeptide (HPP) on rat pancreatic acini has been studied. It was found that HPP stimulated amylase and lipase release from the acini. The secretory response of acini to HPP was dose-dependent in a sigmoidal fashion. Between 10(-9) M and 10(-8) M concentration of HPP there was a slow increase of enzyme release to about 40-60% over basal release. At concentrations of HPP above 10(-8) M there was a rapid increase of enzyme release, amounting to 4-6 times over basal release at 10(-6) M concentration of HPP. The potency of HPP compared to other secretagogues at 10(-7) M concentration was 45% of CCK, 60% of carbachol and 75% of secretin. HPP did not inhibit the effect of CCK, secretin and carbachol on amylase release. The amylase release stimulated by HPP was accompanied by an increase in 45Ca2+ efflux. Atropine or dibutyryl cyclic GMP did not influence the effect of HPP. It is concluded that HPP stimulates the release of enzymes from rat pancreatic acini and that Ca2+ may be a mediator for this secretion.     

Relationship between intravenous ethanol, alcohol-induced inhibition of pancreatic secretion and plasma concentration of immunoreactive pancreatic polypeptide, vasoactive intestinal peptide, and somatostatin in man

We have studied in seven men, consuming less than 50 g alcohol daily, the effect of intravenous (i.v.) ethanol on (a) hormonally (secretin + CCK PZ) submaximally stimulated pancreatic secretion and (b) blood levels of pancreatic polypeptide (PP), vasoactive intestinal peptide (VIP) and somatostatin. After intravenous ethanol (600 mg/kg), pancreatic secretion decreased in all subjects and plasma levels of PP and VIP increased significantly. Moreover, there was a significant correlation between the mean inhibition of chymotrypsin output and the mean increase in PP plasma levels during the first 45 min following ethanol infusion. Therefore i.v. infusion of alcohol elicits release of PP and VIP and PP release could explain in part at least the alcohol-induced pancreatic inhibition observed in non-alcoholic men.     

Meal stimulated levels of pancreatic polypeptide (PP) and vasoactive intestinal polypeptide (VIP) in gastroplasty for morbid obesity

Plasma concentrations of pancreatic polypeptide (PP) and vasoactive intestinal polypeptide (VIP) were measured after a meal consisting of 11 ml meat extract and 40 ml of 20% soya oil in 11 patients before and 3 months after gastroplasty for morbid obesity. Gastroplasty results in a small proximal pouch with a narrow stoma allowing delayed emptying into the distal pouch, and consequently postprandial distension of the proximal pouch. Postprandial plasma PP increased significantly (P less than 0.01) independent of gastroplasty. PP is therefore not involved in the early satiety after gastroplasty. Postprandial plasma VIP increased significantly from fasting levels both before and after gastroplasty (P less than 0.05). Only 10 min after a meal, the median value of VIP was significantly higher after than before gastroplasty (P less than 0.02) and may be caused by distension of the proximal pouch.     

Effect of proglumide, a cholecystokinin receptor antagonist, on caerulein-stimulated pancreatic enzyme secretion and pancreatic polypeptide release in the dog

In five conscious dogs we studied the effect of proglumide, a cholecystokinin (CCK) antagonist, on caerulein-stimulated pancreatic secretion and release of pancreatic polypeptide (PP). Graded doses of caerulein (15-240 ng/kg per h) were infused intravenously. Experiments were repeated with a fixed infusion of proglumide (40 mg/kg per h). Release of PP following increasing doses of caerulein was significantly inhibited by proglumide (P less than 0.01). However, proglumide did not significantly affect caerulein-stimulated pancreatic protein secretion. Proglumide might be useful in defining the physiological role of CCK.     

Effect of adding albumin to solutions of cholecystokinin on pancreatic protein output and pancreatic polypeptide release

In four conscious dogs with chronic gastric and pancreatic Thomas fistulas we studied the effect of 99% pure cholecystokinin-33 (CCK-33) solutions on pancreatic secretion and PP release. CCK-33 was dissolved in 0.154 M NaCl alone or in the same solution containing 1 g per 100 ml dog albumin. The response of pancreatic protein output to increasing doses of CCK-33 (0.5, 1, 2, 4 IDU/kg per h) was significantly $\text{(P < 0.05)}$ higher when CCK was dissolved in NaCl with albumin than in NaCl alone. These results were confirmed by measuring CCK immunoreactivity in samples from tips of infusion lines by a gastrin radioimmunoassay. Release of pancreatic polypeptide (PP) following increasing doses of CCK-33 was also significantly $\text{(P < 0.05)}$ elevated when CCK was dissolved in an albumin-containing solution. There was a significant $\text{(P < 0.02)}$ correlation between plasma concentrations of PP and pancreatic protein output.This study suggests that albumin should be added to CCK-33 solutions to preserve biological activity. The biological effect of CCK-33 may be substantially underestimated if albumin is omitted.     

Elevated levels of circulating pancreatic polypeptide in inflammatory and infectious disorders

Circulating levels of pancreatic polypeptide (PP) were found to be elevated when compared to healthy controls in 54% of patients with chronic inflammatory connective tissue disorders (SLE, rheumatoid arthritis, scleroderma, mixed connective tissue disease and temporal arteritis) and in 96% of patients with acute viral or bacterial infections. Significant positive correlations were obtained between the serum values of PP and those of haptoglobin or orosomucoid. Accompanying successful anti-inflammatory treatment of patients with autoimmune disorders, a reduction of PP levels was observed. The findings suggest that the magnitude of increase in PP was associated with the degree of the inflammatory activity. Raised PP levels may contribute to the alterations in carbohydrate and lipid metabolism observed during active inflammatory diseases in man.     

Increased serum pancreatic polypeptide and serum gastrin secretion in patients with functional dyspepsia: correlation to the shape of the duodenal loop

Simultaneous measurement of food-stimulated serum pancreatic polypeptide and serum gastrin was carried out in 18 patients with functional dyspepsia and correlated to the shape of the duodenal loop. Significantly higher serum concentrations of pancreatic polypeptide and gastrin were encountered in patients with an abnormal shape of the duodenal loop compared to patients with a normal shape. Although no cause could be given to the phenomenon it may be taken into account when evaluating hormone profiles in patients with functional dyspepsia.     

A new in vitro model for studies of pancreatic polypeptide secretion and biochemistry

A new model tissue (pseudoislet) is described for studies of pancreatic polypeptide (PP) secretion and biochemistry. It consists of islet-like aggregates of canine pancreatic endocrine cells which are formed and maintained on tissue culture. Immunocytochemical staining revealed that pseudoislets prepared from the duodenal end of the pancreas contained a predominance (40-60%) of F cells (the PP secreting cell). Also present were 10-25% exocrine cells and an equal proportion of A, B and D cells. Several studies were conducted to characterize the pseudoislets' capacity to secrete PP. Basal rates of PP release and the concentration of PP per pseudoislet remained constant during four weeks of culture. Stimulation at weekly intervals by carbachol (0.1 mM) resulted in a stable secretory rate for 2 weeks, that declined progressively at weeks 3 and 4. When studied in a perfusion system, carbachol-stimulated PP release occurred in a biphasic pattern, similar to the well-recognized biphasic release of insulin from perifused rat islets. Dose-response curves of four cholinergic agonists revealed clear differences in secretagogue activity. Acetylcholine and methacholine were found to be equipotent, followed in order of potency by carbachol and bethanechol. These histologic and secretory data show that canine pseudoislets are healthy tissues composed of a high proportion of F cells which secrete PP in response to cholinergic stimulation. The data suggest that the cultured canine pseudoislet model provides an excellent system useful in studies of PP secretion and biosynthesis.     

Meal-stimulated and atropine-inhibited secretion of pancreatic polypeptide in healthy subjects, members of MEA I families and patients with malignant endocrine tumours of the gastrointestinal tract

Pancreatic polypeptide has been suggested as a marker for endocrine malignancies of the gastrointestinal tract. However, the secretion of PP shows great intra- and inter-individual variation, causing both false negative and positive results. In order to reduce these risks, we have evaluated a new combined stimulatory and inhibitory test of PP secretion. Six healthy subjects, 23 members of three MEA I families, seven patients with malignant pancreatic endocrine tumours and four patients with carcinoid tumours of the gastrointestinal tract were subjected to a standardized test meal, followed by intravenous atropine 60 min after the start of the meal. Serum PP was monitored during 2 h. In healthy subjects the meal caused a rapid increase in serum PP within 20 min and intravenous atropine caused a significant (P less than 0.05) decrease of serum PP within 15 min. Patients with malignant endocrine pancreatic tumours or carcinoids had a delayed response after the test meal, with maximum levels at 45 min, but still with a significant inhibition by atropine. Even tumour patients with initially normal or slightly increased basal PP levels showed this secretion pattern. Healthy members of MEA I families displayed identical PP curves to healthy subjects, whereas members with elevated basal PP levels who had been previously affected by hyperparathyroidism and/or prolactinomas showed similar secretion patterns to pancreatic tumour patients. We think that a meal stimulatory test is of great value in the diagnosis of gastrointestinal endocrine tumours and also in the identification of subjects with the MEA I trait, who are at high risk of having pancreatic endocrine tumours.     

Effect of truncal vagotomy on intestinal phase of pancreatic polypeptide release in dogs

In order to elucidate the role of the vagus nerve in the intestinal phase of pancreatic polypeptide (PP) release, mongrel dogs were given a 4-min intraduodenal infusion of saline, 20% glucose, or 10% soybean oil solution (50 ml each), before and one month after truncal vagotomy including pyloroplasty (TV). The saline infusion did not change the basal PP level, while the glucose infusion elicited a monophasic transient PP release, and the soybean oil infusion elicited a monophasic prolonged PP release in the intact dogs. The PP response following glucose infusion was almost abolished after TV, while the PP response to fat was attenuated, but a significant increase was nevertheless observed after TV. These results suggest that the vagus nerve has an important role in the intestinal phase of PP release and that other factors, e.g. hormonal, might also be involved in the regulatory mechanism, especially after fat loading.     

Long cytoplasmic processes in pancreatic polypeptide cells

Pancreatic polypeptide (PP) cells were studied in human endocrine pancreatic tumours and in normal human pancreata by immunohistochemical techniques and electron miscroscopy. The existence of long cytoplasmic processes was demonstrated both in tumours and normal tissue. These processes are in close contact with other endocrine cells or with acinar cells. This particular morphological aspect suggests that PP cells may control the function of other cells via paracrine secretion.     

Bovine pancreatic polypeptide (bPP) undergoes significant changes in conformation and dynamics upon binding to DPC micelles

The pancreatic polypeptide (PP), a 36-residue, C-terminally amidated polypeptide hormone is a member of the neuropeptide Y (NPY) family. Here, we have studied the structure and dynamics of bovine pancreatic polypeptide (bPP) when bound to DPC-micelles as a membrane-mimicking model as well as the dynamics of bPP in solution. The comparison of structure and dynamics of bPP in both states reveals remarkable differences. The overall correlation time of 5.08ns derived from the 15N relaxation data proves unambiguously that bPP in solution exists as a dimer. Therein, intermolecular as well as intramolecular hydrophobic interactions from residues of both the amphiphilic helix and of the back-folded N terminus contribute to the stability of the PP fold. The overall rigidity is well-reflected in positive values for the heteronuclear NOE for residues 4-34.The membrane-bound species displays a partitioning into a more flexible N-terminal region and a well-defined alpha-helical region comprising residues 17-31. The average RMSD value for residues 17-31 is 0.22(+/-0.09)A. The flexibility of the N terminus is compatible with negative values of the heteronuclear NOE observed for the N-terminal residues 4-12 and low values of the generalized order parameter S(2). The membrane-peptide interface was investigated by micelle-integrating spin-labels and H,2H exchange measurements. It is formed by those residues which make contacts between the C-terminal alpha-helix and the polyproline helix. In contrast to pNPY, also residues from the N terminus display spatial proximity to the membrane interface. Furthermore, the orientation of the C terminus, that presumably contains residues involved in receptor binding, is different in the two environments. We speculate that this pre-positioning of residues could be an important requirement for receptor activation. Moreover, we doubt that the PP fold is of functional relevance for binding at the Y(4) receptor.     

Immunohistochemical identification and localization of pancreatic polypeptide cells in the pancreas and gastrointestinal tract of the human fetus and adult man

Summary Pancreatic polypeptide (PP)-containing cells were detected by using anti-bovine PP (BPP) serum in the pancreas and gastrointestinal tract of human fetuses, premature infants and in the pancreas, antrum and jejunum of adult man obtained by biopsy from patients with normal gastroduodenal endoscopy. The localization was established by studying the distribution of PP cells in comparison to the distribution of glucagon-, somatostatin- and insulin cells. The first PP cells are seen in the pancreas at 10 weeks of gestation. They are located preferentially in the lower part of the head of the pancreas. The specificity of immunocytological reaction was ascertained by the inhibition of the reaction by bovine pancreatic polypeptide, glucagon and insulin did not modify the immunocytological reaction.     

Effect of physiological increments of blood glucose on plasma somatostatin and pancreatic polypeptide levels in dogs

The present study was designed to determine the effects of physiological increments of plasma glucose levels upon basal and stimulated plasma somatostatin and pancreatic polypeptide levels. In seven conscious dogs the elevation of plasma glucose levels by 30-40 mg/dl did not change basal somatostatin and pancreatic polypeptide levels. During stimulation of these two hormones by acetylcholine and the octapeptide of cholecystokinin intravenous infusion of glucose elicited a significant decrease of somatostatin levels by 30 pg/ml and of pancreatic polypeptide levels by 300 pg/ml. The present data demonstrate that a physiological elevation of plasma glucose levels inhibits stimulated but not basal somatostatin and pancreatic polypeptide levels which may be of importance for nutrient entry and metabolism.     

Comparison of enkephalin and atropine in the inhibition of vagally stimulated gastric and pancreatic secretion and gastrin and pancreatic polypeptide release in dogs

Enkephalins have been detected in vagal nerves and myenteric plexus neurons but no study has been performed to determine their action on vagally stimulated gastric and pancreatic secretion. In this study we infused IV methionine-enkephalin (Met-enk) alone, naloxone (a pure opiate antagonist) alone, or their combination before, during and after vagal stimulation in 4 dogs with esophageal, gastric and pancreatic fistulas. For the comparison, atropine was given before, during and after vagal stimulation in the same animals. Vagal stimulation was obtained by 15 min sham-feeding, which produced an increase in gastric H⁺ output to a peak of about 75% of the maximal response to pentagastrin and pancreatic protein secretion amounting to about 71% of the maximal response to caerulein. It was accompanied by a significant rise in serum gastrin and pancreatic polypeptide (PP) levels. Met-enk inhibited significantly both gastric H⁺ and pancreatic protein secretion and reduced plasma PP but not gastrin levels. Similar effects were obtained after the administration of atropine. The effects of Met-enk were partly reversed by the addition of naloxone. We conclude that (1) enkephalin suppresses vagally stimulated gastric and pancreatic secretion and plasma PP release; (2) these secretory effects of enkephalin seem to be mediated by opiate receptors and could be explained by its inhibitory action on acetylcholine release (“anticholinergic” action) in the stomach and the pancreas.     

Amino Acids in Plasma and CSF and Monoamine Metabolites in CSF: Interrelationship in Healthy Subjects

Plasma and cerebrospinal fluid (CSF) concentrations of amino acids were measured in 65 healthy volunteers (50 men and 15 women). The CSF levels of the monoamine metabolites homovanillic acid (HVA), 3-methoxy-4-hydroxyphenylethylene glycol (MOPEG), and 5-hydroxyindoleacetic acid (5-HIAA) were also determined. Sex differences were observed in both plasma and CSF amino acid levels as well as in the relationship between these concentrations. No significant correlations were observed between the CSF levels of HVA and 5-HIAA, and the concentrations of their precursor amino acids in either plasma or CSF. The MOPEG level in CSF correlated positively with the plasma concentrations of several amino acids.     

人G-CSF转基因鼠的稳定遗传与表达

利用人粒细胞集落刺激因子（Ｇ－ＣＳＦ）基因组基因作为目的片段,将其受控于２．６ｋｂ的小鼠乳清酸蛋白（ＷＡＰ）基因的调控区下,通过显微注射法获得了两只整合有人Ｇ－ＣＳＦ转基因小鼠,通过繁殖建立了稳定的转基因系．一些表型参数测定表明转基因鼠与正常鼠无明显差别．通过ＲＴ－ＰＣＲ及Ｓｏｕｔｈｅｒｎｂｌｏｔ检测,在乳腺表达出人Ｇ－ＣＳＦ,为乳腺表达外源蛋白质及今后大动物研究奠定了基础．     

Pancreatic polypeptide response to ethanol in humans and dogs

We studied the effect of a drink of various concentrations of pure ethanol and several commonly ingested alcoholic beverages on plasma levels of immunoreactive pancreatic polypeptide in six healthy human volunteers and compared the results to a protein-rich meal. A drink of distilled water (250 ml) and of pure ethanol (250 ml or 125 ml in the case of 40% v/v ethanol) in concentrations (4, 10, 20, and 40%, v/v) normally present in beer, wine, liquor and whisky did not stimulate plasma pancreatic polypeptide levels above basal. Neither beer, red and white wine (250 ml each) nor whisky (125 ml) caused an increase in basal plasma pancreatic polypeptide levels. The 90-min integrated plasma pancreatic polypeptide response to the protein-rich meal was significantly reduced by an additional drink of 250 ml of white wine ($\text{5987 ± 1315}$ versus $\text{4126 ± 809}\text{pmol · min}{}^{\mathrm{?1}}\text{· 1}{}^{\mathrm{?1}}$). An intravenous infusion of ethanol (300 mg · kg^?1 over 30 min) did not increase plasma pancreatic polypeptide levels above basal.In six dogs with gastric and duodenal fistulas the infusion of pure ethanol into a peripheral vein, into the stomach or into the duodenum did not alter plasma pancreatic polypeptide levels. When ethanol (200 ml of either 1.8, 10 or 40%, v/v) was given as an intragastric bolus injection, only 40% ethanol caused an increase in the mean 90-min integrated plasma pancreatic polypeptide response which was only one-twelfth of the pancreatic polypeptide response to an oral mixed meat meal (35 g · kg^?1). We conclude that in man neither an intravenous infusion nor a drink of ethanol in concentrations normally present in beer, wine and whisky, release pancreatic polypeptide. Also, beer, red and white wine and whisky have no effect on plasma pancreatic polypeptide concentrations. In dogs, a large amount of intragastric ethanol was needed to produce a very small rise in plasma pancreatic polypeptide levels. These results do not favour the hypothesis that, in man and dog, pancreatic polypeptide is the hormonal mediator of the ethanol induced inhibition of exocrine pancreatic secretion.     

Identical immunoreactivity of afferents to the rat suprachiasmatic nucleus with antisera against avian pancreatic polypeptide,molluscan cardioexcitatory peptide and neuropeptide Y

Summary Avian pancreatic polypeptide (APP)-like, molluscan cardioexcitatory peptide (FMRF)-like and neuropeptide Y (NPY)-like immunoreactivities were studied in a secondary visual pathway in rat brain. The cell bodies of this pathway are located in the lateral geniculate nucleus and its terminal plexus is found in the suprachiasmatic hypothalamic nucleus (SCN). The neurons and terminal plexus demonstrated by antiserum to each peptide are identical, and immunoreactivity is blocked by preabsorption of each antiserum with a low concentration of the antigen against which it was raised. Immunoreactivity is also blocked by preabsorption of each antiserum with either NPY or APP. In contrast, APP- and NPY-like immunoreactivities are blocked only partially when these antisera are preabsorbed with concentrations of FMRF as high as 100 M. Since NPY is the only one of these peptides that has been isolated from mammalian brain, we conclude that NPY is the endogenous CNS peptide produced by neurons of the lateral geniculate-SCN projection.