Pepsinogen Secretion Research Articles

Gastric acid secretion, serum pepsinogen I, and serum gastrin in Japanese with gastric hyperplastic polyps or polypoid-type early gastric carcinoma.

We determined the maximum secretion of gastric acid and the fasting serum levels of pepsinogen I and gastrin in Japanese patients with gastric hyperplastic polyps or polypoid-type early gastric carcinoma, comparing those findings with observations in control subjects. Both the maximum acid secretion and fasting levels of serum pepsinogen I were significantly lower in the patients with gastric hyperplastic polyps or polypoid-type early gastric carcinoma than in the controls. Fasting serum gastrin levels were significantly higher in the patients with gastric hyperplastic polyps than in the other two groups of subjects. These data demonstrated that the combination of hypochlorhydria, a low level of pepsinogen I, and hypergastrinemia (type-A gastritis) was common in the patients with gastric hyperplastic polyps, whereas hypochlorhydria and a low pepsinogen I without hypergastrinemia (type-B gastritis) were common in those with polypoid-type early gastric carcinoma.

Regulation of pepsinogen secretion

Regulation of pepsinogen secretion

Chief cells possess a receptor with high affinity for PACAP and VIP that stimulates pepsinogen release.

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a 38-amino acid peptide of the secretin-vasoactive intestinal peptide (VIP) family. To investigate whether PACAP alters chief cell function, we prepared isolated chief cells (> 90% pure) from guinea pig stomach. PACAP-38, PACAP-27, VIP, and secretin all caused a threefold increase in pepsinogen release. The dose-response curves of PACAP-38, PACAP-27, and VIP were biphasic, whereas with secretin it was not. The first phase comprised 40% of maximal release, and each of the three peptides (PACAP-38, PACAP-27, and VIP) were equipotent (EC50 0.1-0.3 nM). For the second phase, comprising 60% of maximal release, the relative potencies were PACAP-38 > PACAP-27 = VIP. 125I-labeled secretin, 125I-VIP, and 125I-PACAP-27 all demonstrated saturable binding to chief cells. Binding of both 125I-PACAP-27 and 125I-VIP was inhibited completely and with similar potencies by PACAP-38, PACAP-27, and VIP. Secretin had a > 500-fold lower affinity than PACAP-38 for displacing both 125I-PACAP-27 and 125I-VIP. With 125I-secretin, secretin was the most potent, and was 197 times more potent than PACAP-38, which was 6-8 times more potent than both PACAP-27 and VIP. We conclude that both PACAP-38 and PACAP-27 stimulate pepsinogen secretion from dispersed chief cells. In contrast to a number of other tissues, no evidence for a high-affinity receptor that interacted only with PACAP was found. PACAP and VIP interact with equal high affinity with a common receptor and with low affinity with the secretin receptor.

Effects of Ostertagia ostertagi infection on secretion of metabolic hormones in calves

Summary Effects of Ostertagia ostertagi infection on secretion of insulin, pancreatic glucagon, cortisol, gastrin, and pepsinogen were studied in calves inoculated with 100,000 (group 1) or 10,000 (group 2) O ostertagi infective larvae weekly for 14 weeks. Plasma insulin concentrations in both inoculated groups were lower than those in a noninfected (group 3) control group. The differences between group 1 and group 3 were significant (P < 0.05) at 2 and 12 weeks after initial inoculation. Plasma pancreatic glucagon and cortisol concentrations of groups 1 and 2 did not differ significantly from those of the control group, although plasma pancreatic glucagon concentration was consistently lower in group-1 calves from 4 weeks to the end of the study. Plasma pepsinogen and serum gastrin concentrations also increased significantly (P < 0.05) in both groups that received inoculations. We concluded that decreased plasma insulin concentrations are contributory to changes in postabsorptive protein metabolism, and that serum gastrin concentrations are more representative of the pathologic changes in the abomasum than are plasma pepsinogen concentrations.

Pepsinogen secretion from streptolysin O-permeabilized chief cells from guinea pig stomach.

To evaluate directly the actions of cellular mediators on pepsinogen secretion, a nearly homogeneous population of dispersed chief cells was permeabilized using the bacterial toxin streptolysin O (30 IU/ml for 10 min). This resulted in the release of > 60% of cellular lactate dehydrogenase activity, whereas cellular pepsinogen levels were not altered. Examination of permeabilized cells using light and electron microscopy revealed preservation of cellular polarity and organelles. Pepsinogen secretion from permeabilized chief cells could be stimulated with increasing concentrations of calcium (300 nM to 10 microM), adenosine 3',5'-cyclic monophosphate (cAMP; 1 microM to 1 mM), phorbol 12-myristate 13-acetate (10 nM to 1 microM), or by addition of carbamylcholine (0.1 mM) to the incubation solution. In the absence of calcium [0.4 mM ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid], activators of protein kinase C stimulated a two- to threefold increase in pepsinogen secretion, and potentiation of secretion was observed when these agents were combined with 0.3 and 1.0 microM calcium. In contrast to the effects of activators of protein kinase C, cAMP-induced pepsinogen secretion was observed only with calcium concentrations > or = 100 nM. Combinations of increasing concentrations of cAMP and calcium resulted in an additive secretory response. This study indicates the utility of streptolysin O-permeabilized chief cells for the study of signal transduction mechanisms that mediate pepsinogen secretion.

M3 muscarinic receptors mediate pepsinogen secretion via polyphosphoinositide hydrolysis in guinea pig gastric chief cells

The muscarinic receptor system involved in pepsinogen secretion from isolated guinea pig gastric chief cells was investigated by evaluating the effect of muscarinic receptor antagonists on carbamylcholine (CCh)-stimulated chief cell responses. CCh stimulated the hydrolysis of polyphosphoinositide in chief cells at the same concentrations as it stimulated pepsinogen secretion. Each of five different muscarinic receptor antagonists, atropine, pirenzepine, 4-diphenylacetoxy-N-methylpiperidine methiodide (4-DAMP), AF-DX116 and scopolamine, inhibited both pepsinogen secretion and inositol phosphate accumulation stimulated by graded concentrations of CCh. The pA2 values of the antagonists calculated from data on inositol phosphate accumulation and pepsinogen secretion (atropine = scopolamine = 4-DAMP greater than pirenzepine greater than AF-DX116) suggest that the muscarinic acetylcholine receptor in gastric chief cells is the M3 subtype. On the other hand, CCh did not affect the adenylate cyclase/cAMP signaling pathway in gastric chief cells. All pA2 values of the antagonists were also in agreement with the Ki values determined by [3H]NMS binding to chief cells. Furthermore, GTP gamma S reduced [3H]acetylcholine binding to chief cell membranes in a concentration-dependent manner. The present study, therefore, suggests that muscarinic M3 receptors, which may be coupled to a G protein, mediate pepsinogen secretion, probably by activation of the polyphosphoinositide second messenger system in guinea pig gastric chief cells.

Basal and Meal‐Stimulated Pepsinogen Secretion in Preterm Infants

SummaryIn order to establish longitudinal normal values for basal and meal‐stimulated pepsinogen secretory function in preterm infants, we studied 44 preterm infants with gestational ages of 28–36 weeks during the period of nasogastric tube feeding. Three age groups were evaluated: gestational ages of 28–30, 31–33, and 34–36 weeks. Basal pepsinogen did not change with postnatal age in any of the groups. Significant meal‐stimulated pepsinogen secretion appeared during the third postnatal week in infants of 28–30 weeks of gestation. In the groups of infants of 31–33 and 34–36 weeks of gestation, significant meal‐stimulated pepsinogen secretion was apparent in the first postnatal week. This study suggests that maturation of pepsinogen secretion appears at 31 weeks of gestation, independent of early feeding.

Basal and meal-stimulated pepsinogen secretion in preterm infants: a longitudinal study.

In order to establish longitudinal normal values for basal and meal-stimulated pepsinogen secretory function in preterm infants, we studied 44 preterm infants with gestational ages of 28-36 weeks during the period of nasogastric tube feeding. Three age groups were evaluated: gestational ages of 28-30, 31-33, and 34-36 weeks. Basal pepsinogen did not change with postnatal age in any of the groups. Significant meal-stimulated pepsinogen secretion appeared during the third postnatal week in infants of 28-30 weeks of gestation. In the groups of infants of 31-33 and 34-36 weeks of gestation, significant meal-stimulated pepsinogen secretion was apparent in the first postnatal week. This study suggests that maturation of pepsinogen secretion appears at 31 weeks of gestation, independent of early feeding.

Y2 receptors for peptide YY and neuropeptide Y on dispersed chief cells from guinea pig stomach.

Peptide YY (PYY) and neuropeptide Y (NPY) inhibit agonist-induced adenosine 3',5'-cyclic monophosphate (cAMP) production and pepsinogen secretion from chief cells. We used radiolabeled PYY and NPY to characterize receptors on chief cells from guinea pig stomach. Binding of 125I-labeled PYY was rapid (70% maximal within 10 min) and specific (not inhibited by secretin, vasoactive intestinal peptide, cholecystokinin, carbachol, prostaglandin E2, forskolin, or cholera toxin). Measurement of the ability of PYY to inhibit binding of 125I-PYY indicated the presence of 1.8 x 10(3) high-affinity [dissociation constant (Kd) = 1.7 nM] and 5.1 x 10(4) low-affinity (Kd = 83.3 nM) sites/cell. Internalization of bound 125I-PYY was suggested by slow and incomplete dissociation in the presence of unlabeled PYY (50% after 2 h) and was examined further by measuring residual binding after washing with acetic acid (pH 2.5), glycine (pH 10.5), or trypsin. After 30 min at 37 degrees C, internalization of radioligand was evidenced by the failure of washing with these solutions to remove 50-65% of bound radioactivity. At 4 degrees C, internalization of 125I-PYY was nearly abolished. Binding of 125I-PYY and 125I-NPY was inhibited by NPY-(13-36) but not by [Leu31,Pro34]NPY indicating that these are Y2 receptors. In guinea pig chief cells, PYY and NPY modulate cAMP-mediated pepsinogen secretion by interacting with specific high-affinity Y2 receptors.

Cellular distribution of gastric chief cell protein kinase C activity: differential effects of diacylglycerol, phorbol esters, carbachol, and cholecystokinin.

Stimulation of chief cells with carbachol or cholecystokinin (CCK) results in the production of inositol trisphosphate (IP3) and diacylglycerol (DAG). Although IP3 increases cell calcium concentration, thereby stimulating pepsinogen secretion, the role of DAG and its target, protein kinase C (PKC), is less clear. To examine the relation between the cellular distribution of PKC activity and pepsinogen secretion, we determined PKC activity in cytosolic and membrane fractions from dispersed chief cells from guinea pig stomach. To validate our assay, we studied the actions of the phorbol ester PMA. PMA caused a rapid, dose-dependent, 6-fold increase in pepsinogen secretion and membrane-associated PKC activity. Similarly, dose-response curves for pepsinogen secretion and the increase in membrane-associated PKC activity induced by a membrane-permeant DAG (1-oleoyl-2-acetylglycerol) were superimposable. In contrast, CCK (0.1 nM to 1.0 microM) and carbachol (0.1 microM to 1.0 mM) caused a 4-fold increase in pepsinogen secretion, but did not alter the distribution of PKC activity. These results indicate that in gastric chief cells, PMA- and DAG-induced pepsinogen secretion is accompanied by increased membrane-associated PKC activity. However, the cellular distribution of PKC activity is not altered by CCK or carbachol.

Role of intracellular Ca2+ and the calmodulin messenger system in pepsinogen secretion from isolated rabbit gastric mucosa.

Both carbachol (10(-4)-10(-3) mol/l) and cholecystokinin octapeptide (CCK-8) (10(-8)-10(-6) mol/l) significantly stimulated the release of pepsinogen from rabbit gastric mucosa maintained in organ culture (213-216% and 143-261% of control, respectively, p less than 0.05-0.01). The secretion was not affected by removing Ca2+ from the culture medium with ethylene glycol tetra-acetic acid. Verapamil failed to inhibit the secretion of pepsinogen induced by the drugs in ordinary culture medium containing Ca2+. In contrast, nicorandil (10(-6)-10(-4) mol/l) attenuated the release of pepsinogen by the drugs in a dose dependent manner, regardless of the presence or absence of Ca2+ in the culture medium. W-7 (10(-6)-10(-4) mol/l) and W-5 (10(-5) and 10(-4), or 10(-6) mol/l) reduced significantly the secretion of pepsinogen induced by carbachol (53-71% and 63-81% of control, respectively, p less than 0.05-0.01) and that by CCK-8 (49-67% and 66-76% of control, respectively, p less than 0.01) in the Ca2+ containing medium. However, W-7 did not show significant inhibition of cyclic adenosine monophosphate (cAMP) and forskolin induced pepsinogen secretion. These findings indicate that the calmodulin messenger branch that is activated by a rise of intracellular Ca2+ mobilised in cytosol from its intracellular, but not extracellular, source plays a critical role in pepsinogen secretion induced by carbachol and CCK-8. It seems likely that an increase in cAMP in cytosol does not provoke any calmodulin mediated pepsinogen secretion.

Electron microscopy of the oxynticopeptic cells of the gastric glands and the intestinal glands of the caecum of the guineapig.

Histomorphology of the gastric and intestinal glands was investigated in 19 sexually mature, adult guineapigs by light and transmission electron microscopy. Gastric glands exhibited the cytological characteristics of oxynticopeptic cells capable of both hydrochloric acid (HCl) and pepsinogen secretion. In the literature, occurrence of oxynticopeptic cells in the proventriculus of the domestic fowl (Toner, 1963; Bell & Freeman, 1971) and in the gastric glands of frogs has been reported (Sedar, 1961; Patt & Patt, 1969; Forte & Forte, 1970). It has been claimed by other investigators (Herriot et al., 1938; Long, 1967) that simultaneous secretion of HCl and pepsinogen by a single, not completely differentiated 'pure' cell type, was highly effective for rapid conversion of the zymogen to active enzyme. Under the light microscope with haematoxylin and eosin stain, the protein secreting activity of gastric glands in guineapigs was masked by the HCl secreting activity, thus morphologically resembling the oxyntic cells. Therefore, different cell types, for example protein-secreting peptic cells and the acid-secreting oxyntic cells, could not be distinguished on the basis of their morphology and staining affinity. For histochemical evaluation of the sections with stains-all method, most cells in the gastric glands responded by a positive reaction to protein. Further, protein containing cells were seen in the intestinal glands of the guineapig caecum. The function of this cell type was correlated with caecotrophic food habits of this species.

Gastric Secretory Abnormalities in Duodenal Ulcer: Primary or Secondary toHelicobacter pyloriInfection?

Hypersecretion of gastric acid, gastrin, and pepsinogen are considered to be causally related to duodenal ulcer diathesis. Until recently, these abnormalities have been considered to be primary and largely genetically determined. However, Helicobacter pylori infection has been shown to be responsible for several of the abnormalities of gastric secretion in duodenal ulcer. H. pylori infection is not only associated with chronic active inflammation but also with a reduction of somatostatin producing D-cells and somatostatin concentrations in the gastric mucosa. The reduced inhibitory action of somatostatin on the secretion of gastric acid, gastrin, and pepsinogen may be responsible for the hypersecretory state of the stomach in duodenal ulcer. These recent findings have drastically changed our understanding of the pathogenesis of duodenal ulcer.

Control of pepsinogen secretion

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Prostaglandin E2 desensitizes cAMP-mediated pepsinogen secretion in chief cells.

To evaluate whether pretreatment with prostaglandin E2 (PGE2) could desensitize pepsinogen secretion in chief cells from guinea pig, chief cells were pretreated with 10 microM PGE2 for up to 30 min. Desensitization of subsequent PGE2-stimulated secretion was maximal after 15 min, averaging only 29 +/- 9% (SE) of pepsinogen secretion in control cells stimulated with 10 microM PGE2. Desensitization was half-maximal with 30 nM PGE2. PGE2 pretreatment at 4 degrees C did not cause desensitization. In cells pretreated with 10 microM PGE2 for 15 min and then given 60 min to recover, responsiveness increased to 79 +/- 7% of that for control cells stimulated with PGE2. Thus the desensitization was reversible. Pretreatment with PGD2 and PGF2a did not alter subsequent PGE2-mediated secretion. PGE2-induced desensitization was heterologous but mediator specific because pepsinogen secretion was reduced in response to adenosine 3',5'-cyclic monophosphate (cAMP)-mediated agents (secretin and vasoactive intestinal peptide) but not Ca(2+)-mediated agents (CCK-8, gastrin, or carbachol). Pretreating chief cells with 10 microM PGE2 did not significantly alter cAMP generation in response to PGE2, secretin, or 3-isobutyl-1-methylxanthine, suggesting that desensitization was not mediated by an alteration in the receptor-coupled adenylate cyclase system. Because PGE2 pretreatment also desensitized pepsinogen secretion induced by the synthetic cAMP analogues 8-BrcAMP and 2'-O-monobutyryl-8-BrcAMP, it is likely that the ability of PGE2 to desensitize pepsinogen secretion in chief cells isolated from guinea pig is due to a mechanism distal to generation of cAMP.

Gastric Mucosa in Female Patients with Fundic Glandular Polyps

To evaluate the characteristics of the gastric mucosa in women with fundic glandular polyps, we examined gastric acid secretion, fasting serum levels of pepsinogen I and gastrin, and gastric histology in 11 female patients with fundic polyps, and compared the results with 30 female controls without endoscopic abnormalities and 50 female patients with gastric foveolar hyperplastic polyps. No significant difference was found in gastric and secretion and fasting serum levels of pepsinogen I and gastrin between the patients with fundic glandular polyps and the control subjects. Histological examination showed that atrophic gastritis was generally not found in the patients with fundic glandular polyps. In contrast, gastric acid secretion and fasting serum levels of pepsinogen I were significantly lower and serum gastrin levels were significantly higher in the patients with foveolar hyperplastic polyps than in the other two groups. Also, patients with foveolar hyperplastic polyps had a higher prevalence and further advanced atrophic gastritis in the fundus than did the other two groups. Our investigations demonstrated that fundic glandular polyps arise from gastric mucosa without atrophic gastritis, whereas foveolar hyperplastic polyps develop from mucosa affected by atrophic gastritis, especially type A gastritis.

Actions of peptide YY and neuropeptide Y on chief cells from guinea pig stomach.

Peptide YY (PYY), found in intestinal endocrine cells, and neuropeptide Y (NPY), a structural analogue of PYY found in neurons, inhibit gastric, pancreatic, and intestinal fluid and electrolyte secretion. We examined the effects of these peptides on dispersed chief cells from guinea pig stomach. PYY and NPY, but not pancreatic polypeptide, starting at nanomolar concentrations, caused a 40-50% inhibition of secretin-, vasoactive intestinal polypeptide-, prostaglandin E2-, and forskolin-induced increases in chief cell adenosine 3',5'-cyclic monophosphate (cAMP) content and pepsinogen secretion. These inhibitory peptides did not alter pepsinogen secretion caused by cholecystokinin, carbamylcholine, A23187, 8-bromo-cAMP, or a phorbol ester. The inhibitory effects of PYY on chief cell cAMP production occurred within 30 s, were independent of phosphodiesterase activity, and did not affect the actions of cholera toxin. However, the inhibitory effects of PYY were abolished when chief cells were preincubated with pertussis toxin, an agent that uncouples inhibitory guanine nucleotide binding (G) proteins from their receptors. In gastric chief cells, PYY and NPY attenuate the stimulatory effects of secretagogues whose actions are mediated by changes in cellular levels of cAMP. PYY-induced attenuation of chief cell adenylate cyclase activity appears to involve activation of inhibitory G proteins.

Somatostatin inhibits pepsinogen secretion via a cyclic AMP-independent pathway

Frog esophageal mucosa contains peptic glands which release pepsinogen in response to a variety of secretagogues and serves as a model to examine the inhibitory action of somatostatin. The pepsinogen secretion in response to bethanechol was inhibited by somatostatin in a noncompetitive fashion. The maximal response induced by bethanechol was reduced and the EC 50 for bethanechol was increased in the presence of somatostatin. On the other hand, somatostatin showed essentially no effect on pepsinogen release evoked by ionophore A23187, dibutyryl cAMP or by forskolin in the presence of atropine. Atropine was included in the incubation mixture to eliminate the effect of acetylcholine released by forskolin from the intrinsic cholinergic neurons also present in the mucosa. Somatostatin did not exert any significant effect on the basal or the forskolin-stimulated cAMP accumulation in the mucosa, nor the basal or the forskolin-stimulated adenylate cyclase activity in the membranes of the peptic cells isolated from the mucosa. Thus, these results seem to suggest that somatostatin inhibits pepsinogen secretion from frog esophageal mucosa by a cAMP-independent pathway.

Difference in Effects of Sodium Fluoride and Cholecystokinin on Pepsinogen Secretion from Isolated Guinea Pig Gastric Chief Cells

In order to further investigate the precise mechanisms of cholecystokinin(CCK)-induced pepsinogen secretion from gastric chief cells, we compared the signal transducing mechanisms activated by CCK with those activated by sodium fluoride (NaF) in isolated guinea pig gastric chief cells. NaF stimulated a monophasic increase in diacylglycerol accumulation with a peak value observed at 15 sec, while CCK strongly stimulated its biphasic accumulation. NaF evoked an increase in initial Ca2+ influx rate with a slow and smooth increase in intracellular free Ca2+ concentration [( Ca2+]i) monitored by fura-2, while CCK stimulated a rapid increase in [Ca2+]i followed by a late sustained phase of [Ca2+]i increase. Lanthanum chloride (La3+) effectively (unlike either nifedipine or verapamil) blocked NaF-stimulated increase in [Ca2+], but it blocked only CCK-stimulated late sustained phase of [Ca2+]i increase. La3+ reduced NaF-or CCK-stimulated maximal pepsinogen secretion to 57.0 +/- 2.5% and 73.1 +/- 3.1% of control, respectively. These results suggest that NaF activates a signal transducing mechanism which seems to be distinct from that activated by CCK, thereby inducing an increase in diacylglycerol accumulation, Ca3+ influx and pepsinogen secretion in guinea pig gastric chief cells.

Helicobacter pyloriStimulates Pepsin Secretion from Isolated Rabbit Gastric Glands

In man, type-B gastritis caused by Helicobacter pylori has been associated with both increased serum pepsinogen in the presence of hypochlorhydria and increased levels of gastric pepsin. We investigated the effect of H. pylori on pepsinogen secretion in vitro and found that a sonicated preparation of H. pylori increased pepsinogen secretion from isolated rabbit gastric glands. This increase was significant after 5 min (p = 0.001), and maximum secretion was obtained after 30 min of incubation. The effect was additive to the secretion achieved by stimulation with carbachol at 10(-4) M plus 10(-4) isobutylmethylxanthine or 10(-8) M cholecystokinin. There was no detectable stimulation of pepsinogen synthesis by 2 h. Lactate dehydrogenase (LDH) release was assayed as an index of cell damage, and no significant LDH release was noted. The secretory factor in the H. pylori sonicate is inhibited by boiling, unaffected by heating at 60 degrees C for 30 min, dialysable, and inactivated by pronase. These data suggest that H. pylori stimulates pepsinogen secretion by a mechanism different from that of other tested stimulants. H. pylori-stimulated pepsinogen release may be a factor in the etiology of type-B gastritis and peptic ulcers.