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Background & Aims: Acid has been shown to stimulate calcitonin gene-related peptide (CGRP) release from peripheral sensory afferent nerve endings in the stomach. The aim of this study was to determine whether endogenous CGRP was involved, by a neurocrine mechanism, in acid-mediated stimulation of somatostatin and inhibition of gastrin release., Methods: A two-compartment sleeve of antral mucosal/submucosal tissue was perfused to determine sensory nerve and endocrine cell responses to luminal acid. CGRP receptor antagonist, CGRP8-37, was used to inhibit the actions of endogenously released CGRP., Results: Perfusion of the antral sleeve lumen with media of increasing hydrogen ion concentration caused pH-dependent increases in CGRP and somatostatin release and decrease in gastrin release. CGRP8-37 inhibited significantly basal somatostatin (-36%) and stimulated basal gastrin (+65%) release (P < 0.02). Furthermore, CGRP8-37 administration prevented luminal acid-mediated inhibition of gastrin release and stimulation of somatostatin release. These results indicate that CGRP8-37 prevented acid-mediated feedback inhibition of gastrin release and acid-induced feedforward somatostatin release., Conclusion: These results suggest that CGRP plays an important role in the response of antral D and G cells to luminal acid and that local effector action of endogenous CGRP participates in regulation of antral regulatory peptide secretion.

Codons of noncoding DNA strands for peptides have been found to code for amino acids with hydropathic properties opposite to those of the native peptides. Synthetic peptides, designated as complementary peptides, with amino acid sequences coded by noncoding DNA strands of several peptide hormones have been shown to bind the native peptides. In some instances, antibodies to these complementary peptides have shown agonist or antagonist properties of the native hormones. In this study a peptide was synthesized based on codons complementary to messenger RNA for the carboxyl-terminal gastrin tetrapeptide. This complementary peptide bound radiolabeled human gastrin (G17). Antibodies to the complementary peptide competitively inhibited the binding of 125I-gastrin by canine fundic mucosal membrane preparations. These antibodies also showed gastrin agonist properties in that they stimulated canine gastric mucosal parietal cell [14C]aminopyrine uptake, used as an index of stimulation of gastric acid secretion. Competitive inhibition of 125I-gastrin binding by membrane receptors for gastrin and stimulation of [14C]-aminopyrine uptake by antibodies to the complementary peptide for the gastrin tetrapeptide are consistent with their recognition, binding, and occupancy of gastrin receptors.

We evaluated effects of duodenojejunal (DJ) feeding on gastric pH and selected gastrointestinal hormones in 13 randomly selected patients in an intensive care unit (ICU). To obtain baseline values for gastric pH, a nasogastric (NG) tube was placed in each patient and gastric pH was measured every 30 minutes for 2 hours. To obtain control values, a Dobbhoff tube was placed fluoroscopically and 0.45 percent saline solution (NaCl), 75 ml, was infused for 1 hour and gastric pH was measured again; the previously placed NG tube was left in position. Then, by randomization, either 0.45 percent NaCl (pH = 5) was continued (n = 6) or a high-nitrogen, isotonic, enteral feeding solution (Osmolite HN, pH = 6.4) (n = 7) was infused, both at 75 ml/h. Gastric pH was noted hourly for 96 hours; antacid (Maalox TC, 15-ml aliquots) was given by NG tube when the pH was 4 or less. After 96 hours, the infusion was stopped and gastric pH was noted for 4 additional hours. Before and during initial saline solution infusion; after 24, 48, 72, and 96 hours of continuous infusion; and 4 hours after stopping the infusion, peripheral venous blood was obtained for measurement of plasma gastric inhibitory polypeptide (GIP) and serum gastrin. Data were analyzed by ANOVA (RMD), Fishers' exact test, and the unpaired t-test. Groups did not differ demographically. Throughout the infusion, gastric pH tended to be higher with the enteral feeding solution than with saline solution, but this was significant only at 24 hours. Less antacid was required with the enteral feeding solution at 24 and 48 hours than with saline solution. Plasma GIP levels were significantly higher with the enteral feeding solution than with saline solution during most of the infusion. Serum gastrin levels did not differ between the groups. In this cohort, infusion of the enteral feeding solution tended to maintain a gastric pH of more than 4 and was associated with increased plasma GIP levels, which may inhibit gastric acid secretion. Early enteral feeding may benefit certain ICU patients.

Human gastrin I heptadecapeptide was administered by constant intravenous infusion to 7 adult male volunteers without gastrointestinal disease, and serum gastrin concentrations and responses of the lower esophageal sphincter (LES) pressure and gastric acid output were measured and compared. Significant responses in LES pressure were found at gastrin infusion rates which produced submaximal gastric acid output. These LES pressure responses were quantitatively smaller than those occurring concomitantly with similar total immunoreactive gastrin levels evoked by administration of a protein meal in the same subjects. These observations suggest that, although increases in serum gastrin concentrations may contribute to increases in LES pressure seen under physiological conditions after feeding, the increase in LES pressure produced by feeding cannot be explained exclusively on the basis of endogenous gastrin release.

The present studies were directed to examine the effect of gastrin-releasing peptide (GRP) on beta-adrenergic stimulated gastrin release by cultured rat antral mucosa and to assess the anatomical relationship between gastrin cells and GRP nerves in rat and human antrum. Peptide-containing cells were identified by application of an avidin-biotin-peroxidase immunocytochemical double staining method utilizing antibodies to GRP and gastrin prepared in rabbits. Rat antral mucosa was cultured for 60 min and gastrin released into the culture medium was measured by radioimmunoassay. Inclusion of antibodies to GRP in culture medium did not affect carbachol-stimulated gastrin release, whereas isoproterenol-stimulated gastrin release into the medium was inhibited significantly by addition of GRP antiserum to the culture medium. GRP-containing neurons and axonal fibers were stained immunocytochemically with diaminobenzidine (reddish-brown specific staining) and were located in the lamina propria adjacent to and surrounding the main lobules of antral glands. After double staining utilizing 4-Cl-1-Naphthol as substrate, blue stained gastrin-containing cells were identified in the middle and deeper regions of antral glands in close proximity to GRP neuronal elements. These studies suggest that beta-adrenergic, but not cholinergic, stimulation of gastrin release is mediated, at least in part, through GRP. They also demonstrate intimate anatomical, as well as functional, relationships between gastrin cells and GRP-containing neurons.

This study was designed to examine and compare the nature of gastrinlike and cholecystokininlike peptides released into the portal and peripheral venous circulation in response to a peptone meal. Six dogs were prepared with portal venous catheters and gastric fistulas. Portal and peripheral venous sera were obtained before and after gastric infusion of a 10% peptone meal. Serum levels of gastrin and cholecystokinin immunoreactive peptides were determined by radioimmunoassay using two distinct peptide region-specific antibody preparations. These separate antibody preparations demonstrated specificity for (a) C-terminal tetradecapeptide gastrin (4-17hG17), heptadecapeptide gastrin (G17), and big gastrin (G34) (gastrin antibody); and (b) all biologically active forms of gastrin and cholecystokinin (gastrin-cholecystokinin antibody). Using the antibody preparation with specificity for gastrin and not cholecystokinin, the mean basal immunoreactive gastrin from portal (8.33 +/- 2.4 fmol/ml, mean +/- SEM) and from peripheral (6.19 +/- 0.9 fmol/ml) venous sera both increased after peptone infusion, with an early peak (2 min in portal and 4 min in peripheral serum) and a second peak at 30 min in both circulations. Measurements using antibodies with specificity for both cholecystokinin and gastrin yielded strikingly different results. The portal venous serum peptide concentration (49 +/- 10 fmol/ml) increased sharply within 30 s after peptone infusion to a single peak at 2 min (139 +/- 37 fmol/ml). The basal peripheral venous serum peptide concentration (43 +/- 8.8 fmol/ml) increased more gradually to a single peak at 8 min (78 +/- 14 fmol/ml). Studies with Sephadex (G-50 superfine) gel chromatography indicated that gastrin released in response to the peptone meal was primarily G17. However, of the peptides released in response to the peptone meal that were recognized by the gastrin-cholecystokinin antibody, greater than 80% were shown to be distinct from gastrin. Gel chromatographic studies demonstrated that peptone meal-stimulated immunoreactive cholecystokinin release consisted of two major peaks, eluting in positions identical to those of intact cholecystokinin (CCK33) and the octapeptide of cholecystokinin (CCK8).

The purpose of this study was to examine and quantify hepatic uptake and degradation of gastrin and cholecystokinin peptides. Rat livers were perfused in situ, without recirculation, with Krebs-Ringer bicarbonate (pH 7.4) containing 10% bovine erythrocytes, gassed with 95% O2-5% CO2. Gastrin and cholecystokinin peptide fragments of various lengths were injected into a portal vein via a sidearm syringe for over 1 min, and hepatic venous effluent was collected every minute for 20 min. After injection of 125I-labeled gastrin peptides more than eight amino acids in length, greater than 95% radioactivity appeared in the hepatic venous effluent, all of which was intact peptide, as determined by immunoprecipitation, trichloroacetic acid precipitation, and Sephadex gel chromatography. Decreasing the chain length to eight or less amino acids resulted in progressive increases in hepatic uptake and degradation of gastrin fragments. Injected cholecystokinin peptides greater than seven amino acids in length traversed the liver intact, whereas smaller cholecystokinin peptides were cleared by the liver. The liver eliminated greater than 90% of the biologically active carboxyl-terminal tetrapeptide amide common to gastrin and cholecystokinin. The results of this study indicate that gastrin and cholecystokinin peptides longer than seven amino acids traverse the liver without significant degradation, however, smaller peptides are progressively cleared during hepatic transit. Therefore, if small gastrin and cholecystokinin peptides from antral and intestinal mucosa are released and reach the portal venous circulation, hepatic inactivation would appear to prevent them from reaching the systemic circulation, precluding their significant contribution to gastric acid secretion and other physiologic functions.

Proximal gastric vagotomy-mucosal antrectomy (PGV-MA) was devised in an attempt to reduce the cephalic and hormonal phases of acid secretion without disturbing gastric emptying. The current study determines the effects of proximal gastric vagotomy (PGV), or PGV-MA on acid secretion, gastrin, and gastric emptying. Twelve dogs underwent measurement of gastric emptying, fasting and postcibal acid production, and fasting and postprandial gastrin levels. The animals then underwent either PGV or PGV-MA and the studies were repeated. PGV markedly decreased basal acid (P less than 0.001); however, there was still a large postprandial acid increase. In contrast, PGV-MA nearly abolished both fasting and postprandial acid secretion (difference from control and PGV significant at P less than 0.001). Gastric emptying was not significantly altered by either procedure. PGV was associated with increased fasting and postprandial gastrin levels, while PGV-MA produced lower gastrin levels at all intervals than either controls or PGV-MA. PGV-MA emulates the effects of truncal vagotomy and antrectomy on acid secretion, without affecting gastric emptying and deserves further investigation as a possible surgical alternative in the treatment of duodenal ulcer disease.

The effects of alterations in availability and access of extracellular media calcium on antral gastrin release were examined in the basal state and in response to cholinergic stimulation in rat antral organ culture experiments. In the presence of either divalent cationic chelator (EGTA) or calcium channel blocker (verapamil, nifedipine), carbachol-stimulated gastrin release was inhibited completely to values that were not significantly different from non-stimulated control. In the absence of added calcium chloride, carbachol stimulated gastrin release during the initial 30 min of culture but not at 69 and 120 min of culture. Inhibition by EGTA and verapamil of carbachol-stimulated gastrin release during the initial 30 min of culture suggests, but does not prove, that these agents may also effect intracellular availability and movement of calcium. Cholinergic stimulation of gastrin release demonstrated a concentration-dependent relationship with extracellular calcium: optimal culture media calcium concentration was 1 mM. In conclusion, these studies indicate that cholinergic stimulation of the gastrin cell requires availability of extracellular calcium.

Recent developments have led to a further appreciation of the various species of circulating gastrin and to provocative tests for the presence of the Zollinger-Ellison syndrome. Studies of serum gastrin levels, together with other studies of physiologic response, have suggested some possible roles of gastrin in the complex gastric acid hypersecretory state that frequently accompanies duodenal ulcer. Finally, investigations of exogenous and endogenous serum gastrin have provided a mechanism to examine the possible physiologic effects of this hormone.

Serum gastrin has been reported to increase after therapy with some agents effective in the treatment of duodenal ulcer (DU). Misoprostol, a prostaglandin E1 analog, is effective in the treatment of DU, with healing rates similar to those achieved with vigorous antacid therapy or H2-receptor antagonists. Misoprostol reduces gastric acid secretion and also possesses cytoprotective properties. This multicenter study examined serum gastrin levels before and after treatment of DU patients with misoprostol. Sera for gastrin measurement were obtained from DU patients after an 8-hr fast, and 15 and 30 min after a standard mixed meal. DU patients were studied before and after two to four weeks of treatment with placebo or misoprostol: in one study, misoprostol 100 micrograms qid (without antacid) was compared with placebo; in the other study, misoprostol at 50- or 200-micrograms qid dosages (with limited antacid, Amphojel up to 54 meq/day) was compared with placebo. In addition, the serum gastrin values obtained in healthy subjects were compared with those from DU patients. Fasting and postprandial serum gastrin concentrations were essentially similar for DU patients and healthy subjects. There were no significant differences, either in fasting serum gastrin or in integrated gastrin responses, in DU patients after treatment with placebo or misoprostol at 100 micrograms (P = 0.32), 50 micrograms, or 200 micrograms doses (P = 0.85). It is concluded that misoprostol, when administered four times daily for two to four weeks at dosages required for the acceleration of DU healing, does not affect serum gastrin levels.

Human gastrin I heptadecapeptide, infused intravenously to healthy volunteers in a dose of 0.5 micrograms/kg/hr, caused a prompt, significant reduction in gastric potential difference (decrease of mucosal negativity), with the peak change at 6 min. This decline in potential difference occurred at a time when the serum gastrin level was between 24 and 83 pg/ml; at the same time, scanning electron microscopic examination of fractographs of parietal cells demonstrated marked increase in canalicular membrane area. This study shows that the decrease in potential difference after gastrin occurs with serum gastrin levels which are in the physiologic range.

Previous studies have questioned the physiological role of gastric inhibitory peptide in inhibiting gastric acid secretion. The present study was designed to examine and compare peptone meal-stimulated gastric acid secretion in dogs after intravenous infusion of rabbit serum containing antibodies to gastric inhibitory peptide or normal rabbit serum (as control). Five dogs were prepared with gastric fistulas. Basal acid output was collected for 90 min through the gastric fistula. After 30 min of basal acid output collection, either rabbit serum containing antibodies to gastric inhibitory peptide or normal control rabbit serum (0.1 ml/kg) was infused intravenously over 1 min. After the basal acid output collection, a 10% peptone meal was infused into the stomach. Gastric acid output was measured by intragastric titration (pH 5.0) for 60 min. Peripheral venous plasma was collected for measurement of gastrin and gastric inhibitory peptide and for binding of endogenous plasma gastric inhibitory peptide by administered antibodies to gastric inhibitory peptide before and at 2, 5, 10, 15, 30, 60, 90, and 120 min after the meal. After intravenous administration of antibodies to gastric inhibitory peptide, 98% +/- 3% (SEM) of endogenous plasma gastric inhibitory peptide was bound by administered antibodies to gastric inhibitory peptide. No binding of endogenous plasma gastric inhibitory peptide was detected after infusion of normal rabbit serum. In dogs receiving intravenous antibodies to gastric inhibitory peptide, both peptone-stimulated gastric acid output and integrated gastrin release responses were increased when compared with dogs receiving normal rabbit serum. With infusion of antibodies to gastric inhibitory peptide, there was a high degree of correlation between the increase in gastric acid output and the increase in integrated gastrin response (r = 0.900, p less than 0.04) that followed the peptone meal. This study, using antibodies to bind endogenous gastric inhibitory peptide, demonstrates the capacity of circulating gastric inhibitory peptide to inhibit meal-stimulated gastric acid secretion. Furthermore, these results support the conclusion that this enterogastrone effect of gastric inhibitory peptide is due, at least in part, to inhibition of gastrin release.

Vagally denervated (Heidenhain) pouch acid outputs and serum gastrin concentrations, basal and in response to feeding, were measured in dogs before and after massive intestinal resection. Both 24-hr and postprandial Heidenhain pouch acid outputs increased (P less than 0.01) after intestinal resection. Increases in serum gastrin concentrations following feeding were greater after massive resection of the small intestine. There was an excellent correlation (r= 0.967; P less than 0.005) between increases in serum gastrin concentrations and Heidenhain pouch acid outputs after intestinal resection. These studies support and are consistent with the hypothesis that the polypeptide hormone gastrin plays a role in the production of the gastric acid hypersecretion which, in both dogs and man, frequently results from massive resection of the small intestine.

The purpose of the present study was to examine stimulation of gastrin release and the synthesis of gastrin directly by measurement of incorporation of [(3)H]tryptophan into gastrin in rat antral mucosal explants maintained in organ culture. Gastrin synthesis and secretion were assessed simultaneously at intervals over the 24-h duration of explant culture. Antral mucosal explants from fed female Wistar rats (4-5 wk, 100-150 g) were cultured at 37 degrees C (95% O(2)/5% CO(2)) in medium containing 70% Trowell-T8 and 10% NCTC-135 without unlabeled tryptophan, 10% dialyzed fetal calf serum and [(3)H]tryptophan (100 muCi/ml). Antral tissue was harvested at regular intervals during 24-h culture periods. Incorporation of [(3)H]tryptophan into immunoreactive gastrin was determined by techniques utilizing double-antibody immunoprecipitation. Antral tissue protein synthesis was assessed by measurements of incorporation of [(3)H]tryptophan into tissue protein of cultured antral explants. In paired experiments, gastrin synthesis and secretion in the presence of dibutyryl cAMP (DBCAMP) were compared to those observed under control conditions. Gastrin and protein specific activity progressively increased with time. Gastrin specific activity at 30 min increased from 3.3+/-0.5 (SEM) to 55.2+/-10.6 fmol [(3)H]tryptophan/pmol gastrin (or from 1.57+/-0.48 to 26.28+/-5.05 pmol [(3)H]tryptophan/mug gastrin) at 24 h: specific activity of antral tissue protein at 30 min increased from 33.6+/-8.4 to 1,660+/-236 fmol [(3)H]tryptophan/mug protein at 16 h. Culturing of explants for 4 h in the presence of cycloheximide (100 mug/ml) inhibited both gastrin synthesis and protein synthesis by greater than 90 and 95%, respectively. DBCAMP (10 mM) significantly increased both the synthesis and secretion of antral gastrin when compared with control cultured explants. Results of these experiments provide direct demonstration of gastrin synthesis by rat antral mucosal explants in organ culture, indicate that both gastrin and total antral protein synthesis are inhibited by cycloheximide, and demonstrate DBCAMP-induced stimulation of both gastrin synthesis and secretion, suggesting the potentially important role of cyclic AMP in gastrin cell function.

Gastrin release was studied from rat antral mucosal cells maintained under tissue culture conditions. Results of experiments with neurotransmitter agonists, antagonists, and modulators indicate the following: Adrenergic mediation of gastrin release occurs in vitro. Adrenergic stimulatory action could be demonstrated by norepinephrine and, more specifically, beta-receptor activators, whereas an alpha-receptor activator was inhibitory. The effects appear to be specific because the agonists stimulate gastrin release at low concentrations and because these effects are blocked by the appropriate antagonists. Because high carbachol concentrations were needed to produce gastrin secretion, and inhibition by atropine occurred also at high concentrations, these effects may be nonspecific. Both carbachol- and norepinephrine-mediated gastrin release are modified by somatostatin and adenosine. Effective modulation of gastrin release by these substances may be relevant in understanding the fine regulation of gastrin release during digestive processes.

Serum gastrin determinations were performed in 32 normal-term infants to determine the level of this hormone in normal infants at birth and its response to normal feeding. Significant differences were noted between newborn cord blood and maternal blood at birth. Further significant elevations in fasting serum gastrins were noted in these infants over the first 72 hr of life. Pre- and postprandial determinations with normal feeding failed to demonstrate a significant elevation in serum gastrin levels following ingestion of protein-containing formulas. These data suggest a relative insensitivity of the release of gastrin from the gastric antrum in response to protein, a powerful mediator of gastrin release in the adult.

Somatostatin-containing cells have been shown to be in close anatomic proximity to gastrin-producing cells in rat antral mucosa. The present studies were directed to examine the effect of secretin on carbachol-stimulated gastrin release and to assess the potential role of somatostatin in mediating this effect. Rat antral mucosa was cultured at 37 degrees C in Krebs-Henseleit buffer, pH 7.4, gassed with 95% O2-5% CO2. After 1 h the culture medium was decanted and mucosal gastrin and somatostatin were extracted. Carbachol (2.5 X 10(-6) M) in the culture medium increased gastrin level in the medium from 14.1 +/- 2.5 to 26.9 +/- 3.0 ng/mg tissue protein (P less than 0.02), and decreased somatostatin-like immunoreactivity in the medium from 1.91 +/- 0.28 to 0.62 +/- 0.12 ng/mg (P less than 0.01) and extracted mucosal somatostatin-like immunoreactivity from 2.60 +/- 0.30 to 1.52 +/- 0.16 ng/mg (P less than 0.001). Rat antral mucosa was then cultured in the presence of secretin to determine its effect on carbachol-stimulated gastrin release. Inclusion of secretin (10(-9)-10(-7) M) inhibited significantly carbachol-stimulated gastrin release into the medium, decreasing gastrin from 26.9 +/- 3.0 to 13.6 +/- 3.2 ng/mg (10(-9) M secretin) (P less than 0.05), to 11.9 +/- 1.7 ng/mg (10(-8) secretin) (P less than 0.02), and to 10.8 +/- 4.0 ng/mg (10(-7) M secretin) (P less than 0.02). Secretin (10(-7) and 10(-8) M) also increased concomitantly culture medium somatostatin concentration. To determine whether secretion inhibition of carbachol-stimulated gastrin release was mediated by somatostatin, antral mucosa was cultured with carbachol, secretin (10(-9)-10(-7) M), and antibodies to somatostatin. Inclusion of somatostatin antibodies in the culture medium abolished the capacity of secretin (10(-7) and 10(-8) M) to inhibit carbachol-stimulated gastrin release. Results of these studies indicate (a) that secretin inhibits carbachol-stimulated gastrin release and (b) that under the conditions of these experiments secretin inhibition of gastrin release is mediated, at least in part, locally through release of antral somatostatin.

The effects of somatostatin on gastrin release and total gastrin immunoreactivity were examined under in vitro conditions in rat antral organ culture experiments. Basal antral gastrin release was inhibited by somatostatin. Total culture gastrin contents (culture medium gastrin plus extracted antral mucosal gastrin) at 6 h were reduced significantly by 10(-5) M (p less than 0.02) and 10(-4) M (P less than 0.01) somatostatin. Gastrin release into the culture media stimulated by the cholinergic agent, carbachol (10(-5) M), was suppressed by somatostatin: at 30 min and 6 h of culture 10(-8) M somatostatin inhibited carbachol-stimulated gastrin release by 66% and 54%, respectively, and 10(-5) M and 10(-4) M somatostatin completely abolished gastrin release. The rate of gastrin release stimulated by carbachol was suppressed significantly by each dose of somatostatin examined (10(-8) M to 10(-4) M). The present studies indicate that somatostatin inhibits both gastrin secretion by cultured rat antral mucosa and total antral culture gastrin contents, and demonstrate that cholinergically-mediated gastrin secretion is inhibited by somatostatin.

The effect of cyclic adenosine and cyclic guanosine nucleotides and theophylline upon gastrin synthesis and secretion were examined in rat antral mucosa maintained in organ culture. In concentration-response experiments, cyclic AMP, dibutyryl cyclic AMP and theophylline stimulated gastrin release and incorporation of [3H]-tryptophan into gastrin: a high degree of positive correlation was demonstrated between gastrin synthesis and gastrin release in response to control and test culture conditions. Cyclic GMP and dibutyryl cyclic GMP also stimulated gastrin secretion to a degree similar to that seen with cyclic AMP. These studies provide support for the proposal that the cyclic nucleotide system is involved in the stimulation of gastrin synthesis and release by the antral gastrin cell.

To define the role of gastrin, if any, in the response of the lower esophageal sphincter (LES) to bethanechol, serum gastrin determinations and LES pressure measurements were made in controls, patients with vagotomy and antrectomy (V&A), and patients with vagotomy and pyloroplasty (V&P). Despite significant differences in mean basal serum gastrin levels no differences were found in mean resting LES pressures among these groups. In controls significant increases in LES pressure occurred after subcutaneous bethanechol, but serum gastrin levels did not change from basal values. Subcutaneous injections of bethanechol produced significantly greater increases in LES pressures in V&P patients than in V&A patients. Serum gastrin levels did not change in either group; however, background serum gastrin concentrations were significantly greater for V&P patients than V&A patients throughout the study. Intravenous infusion of human gastrin I heptadecapeptide in controls significantly increased sphincter responses to bethanechol. Thus, these studies provide evidence to suggest that the LES response to bethanechol is affected by background serum gastrin levels.

The purpose of the present study was to examine the effects of microtubular-microfilament (MT-MF) modifying agents on gastrin release from antral mucosal cells maintained for 3 days under tissue culture conditions. Gastrin levels in the media, determined by radioimmunoassay, were monitored at hourly intervals for 6-8-hr periods. Colchicine, 1 mM, produced mild depression in media gastrin levels and completely inhibited dcAMP-theophylline-induced gastrin release. Ethyl alcohol depressed secretion of gastrin. Conversely, colchicine at 0.01 mM, significantly increased levels of gastrin. Gastrin levels were also significantly increased by tetracaine, 1 mM, and by deuterium oxide, 75% and 37.5%. Cytochalasin D had little effect on resting gastrin levels. Results of these experiments indicate response of gastrin-producing cells maintained under these conditions to a number of test agents; that the secretory responses of gastrin cells to the MT-MF modifying agents are similar to those of other endocrine cells in which concommitant changes in the MT-MF system have been studied, providing support for the proposal that this system is involved in the sequence of intracellular events which leads to gastrin secretion.

Canines with vagally innervated fundic pouches and chronic esophageal fistulas were subjected to sham feeding experiments during which pouch acid output and peripheral serum gastrin levels were measured. These dogs then underwent construction of vagally innervated antral pouches. The sham feeding experiments were repeated after recovery. Preoperatively sham feeding provoked a substantial increase in acid output accompanied by a small serum gastrin increase which did not achieve statistical significance. After creation of the innervated antral pouches, sham feeding evoked an acid secretory response similar to control values. Serum gastrins, however, increased nearly 500 percent in response to sham feeding. Our data support the concept that direct vagal stimulation of the parietal cell mass is the major mechanism by which sham feeding increased acid secretion.

Studies were performed in anesthetized opossums to determine the influence of binding of circulating gastrin with a high titer gastrin antiserum on lower esophageal sphincter pressure. Gastrin antiserum or control antiserum was administered intravenously in successive doses of 0.02, 0.1, and 0.5 ml/kg on separate days. The lower esophageal sphincter pressures were measured for 1 h before and for 1 h after antiserum administration. The control serum caused no binding of opossum circulating gastrin, nor did it modify lower esophageal sphincter pressure. On the other hand, the administration of gastrin antiserum resulted in the binding of 85-90% of circulating gastrin, but it did not reduce sphincter pressure. A continuous infusion of 0.25 mug-kg-1-h-1 of synthetic human gastrin I caused a significant (P less than 0.05) increase in the sphincter pressure, a 30-fold increase in gastric acid output, and a fourfold increase in immunoreactive gastrin in the opossum blood. Prior treatment with 0.1 ml/kg of gastrin antiserum antagonized and 0.2 ml/kg of the antiserum abolished the gastrin-stimulated gastric acid secretion and the stimulating effect of gastrin on lower esophageal sphincter pressure. However, neither dose of antiserum modified basal lower esophageal sphincter pressure. It is concluded that circulating gastrin may be an important determinant of basal sphincter pressure.

It has now been well established that the ulcerogenic syndrome associated with non-beta islet cell tumors of the pancreas is due to excess gastrin release and consequent marked gastric acid hypersecretion. The clinical manifestations may be similar to, but are often more severe and recurrent than, common peptic ulcer. The diagnosis of gastrinoma in patients with this clinical syndrome can be established principally by demonstration of fasting hypergastrinemia, and by application of provocative tests with measurement of serum gastrin in response to intravenous calcium infusion, intravenous secretin injection and feeding of a standard meal. Gastrinomas are usually located within the pancreas, are often multifocal and metastatic, but may be primary in non-pancreatic sites. There is substantial heterogeneity in the molecular forms of circulating and gastrinoma gastrin. Although hypergastrinemia is characteristic of gastrinoma, serum gastrin levels may be increased in disorders other than gastrinoma. Techniques are available to document the presence of gastrin in islet cell tumors and, thereby, to establish these as gastrinomas.

Recent studies have demonstrated that somatostatin-containing cells are in close anatomic proximity to gastrin-producing cells in antral mucosa, suggesting a potential local regulatory role for somatostatin. The purpose of this study was to examine further the relationships between gastrin and somatostatin and the effects of the cholinergic agonist carbachol on content and release of gastrin and somatostatin using rat antral mucosa in tissue culture. Antral mucosa was cultured at 37 degrees C in Krebs-Henseleit buffer, pH 7.4, gassed with 95% O2-5% CO2. After 1 h, the culture medium was decanted and the tissue was boiled to extract mucosal gastrin and somatostatin. Inclusion of carbachol 2.5 X 10(-6) M in the culture medium decreased medium somatostatin from 1.91 +/- 0.28 (SEM) ng/mg tissue protein to 0.62 +/- 0.12 ng/mg (p less than 0.01), extracted mucosal somatostatin from 2.60 +/- 0.30 to 1.52 +/- 0.16 ng/mg (p less than 0.001), and percentage of somatostatin released from 42% +/- 2.6% to 27% +/- 2.2% (p less than 0.01). Carbachol also increased culture media gastrin from 14 +/- 2.5 to 27 +/- 3.0 ng/mg protein (p less than 0.01). Tissue content and release of gastrin and somatostatin were also examined during culture of rat antral mucosa in culture media containing antibodies to somatostatin in the presence and in the absence of carbachol. Incubation with somatostatin antisera, both with and without carbachol, markedly increased culture media concentrations of somatostatin, all of which was effectively bound by antibodies present in the media. Antibody binding of somatostatin was accompanied by significant increases in culture media gastrin concentrations, both in the presence and in the absence of carbachol. Results of these studies support the hypothesis that antral somatostatin exerts a local regulatory effect on gastrin release and that cholinergic stimulation of gastrin release is mediated, at least in part, through inhibition of somatostatin synthesis and release.

The role of calcium in gastrin release was investigated using rat antral organ culture. During the initial 4-h culture interval, in the absence of calcium in the culture medium, gastrin release was not different from that observed with 0.5, 1, and 2 mM calcium. However, after 6 h of culture, gastrin release with 0.5, 1, and 2 mM calcium was significantly greater than that with antral explants cultured in calcium-free media. In the presence of 1 mM calcium in the culture medium gastrin release was stimulated by dibutyryl cyclic AMP, whereas with calcium-free culture medium dibutyryl cyclic AMP was ineffective in stimulating gastrin release. Effects of ionophore A23187 on gastrin release were examined in experiments with culture medium containing no added calcium and with 2 mM calcium. The dose-response to ionophore A23187 (1.2--10 microgram/ml) with 2 mM calcium demonstrated progressive increases in culture media gastrin at 30, 60, and 120 min of culture. Maximal gastrin release occurred with 10 microgram/ml ionophore at each culture interval. Gastrin releases was not stimulated by increasing doses of ionophore when added to calcium-free organ culture media. Results of these experiments suggest that calcium is important in regulation of antral gastrin release and that dibutyryl cyclic AMP-stimulated release of antral gastrin is, at least in part, calcium-dependent. Stimulation of gastrin secretion by ionophore A23187 (in the presence of calcium) further supports the role of calcium in antral gastrin release and suggests that transport of calcium across cellular membranes is important in the coupling of secretory events in the gastrin cell.

Gastrin conjugated to bovine serum albumin was administered to New Zealand white rabbits by repeated injections at a standard immunizing dose of 2 mg BSA-gastrin conjugate, as well as at 0.2 mg (10%) and 0.02 (1%) of BSA-gastrin conjugate. The immediate dose of immunogen (0.2 mg) was also given by multiple simultaneous intradermal injections, with one later booster immunization. Resultant antisera from footpad injected rabbits were found to be of comparable high affinity, which was uninfluenced by the size of the administered dose of antigen conjugate. Antibody binding sites concentrations in these antisera, however, were found to be proportional to immunizing dose. Antibodies to gastrin produced after intradermal injection, although of comparable serum antibody concentrations, were of significantly lower affinity than after footpad immunization. It is concluded that high affinity antisera suitable for use in radioimmunoassay of gastrin can be produced by footpad immunization utilizing a small fraction of the standard immunizing dose of gastrin-bovine serum albumin conjugate.

Conflicting data exist regarding the physiology of serum gastrin production in neonates and infants, and the response of the neonatal gastric antrum to feeding. Normal neonates and infants underwent serial determination of fasting and postprandial serum gastrin levels from birth to 4 months of age. The mean fasting serum gastrin levels in newborns and infants up to 4 months remained considerably higher than the mean maternal levels, the elevations being statistically significant until 2 months of age. In addition, in the first 2 months of life, there was no evidence of postprandial stimulation of serum gastrin levels 30 minutes following normal feeds consisting of breast milk or commercial formula. At 3 and 4 months of age, the response appears to revert to an adult pattern with statistically significant postprandial elevations following normal feeds (p = 0.003 and p = 0.02, respectively). This study confirms the presence of neonatal hypergastrinemia and reveals a persistence of elevated serum gastrin levels through early infancy. A maturation of the antral gastrin release response with postprandial elevations of serum gastrin levels occurs at approximately 3 months of age.

This study was performed to examine the effects of somatostatin on antral gastrin release stimulated by postreceptor increases in adenosine cyclic nucleotide. Increases in intracellular levels of cyclic adenosine monophosphate were achieved through the use of the dibutyryl derivative of cyclic adenosine monophosphate and the phosphodiesterase inhibitor theophylline. The effects of somatostatin on basal and stimulated gastrin release were examined in rat antral organ culture experiments. Inclusion of somatostatin in the culture medium (1 X 10(-8) to 1 X 10(-4) M) resulted in significant inhibition of gastrin release at somatostatin concentrations of 1 X 10(-5) and 1 X 10(-4) M: both doses of somatostatin inhibited gastrin release by approximately 52% at 30 min and by 32% at 6 h. Gastrin release stimulated by dibutyryl cyclic adenosine monophosphate was significantly inhibited by 1 X 10(-5) and 1 X 10(-4) M somatostatin to 133% and 121% at 30 min and 77% and 98% at 6 h, respectively. Gastrin release stimulated by theophylline (1 mM) was also significantly inhibited by somatostatin in doses ranging from 1 X 10(-6) to 1 X 10(-4) M. The degree of inhibition by somatostatin of dibutyryl cyclic adenosine monophosphate- and theophylline-stimulated gastrin release declined over the duration of culture. In conclusion, these results suggest that somatostatin inhibits adenosine cyclic nucleotide-stimulated gastrin release by acting at a point distal to the formation of cyclic adenosine monophosphate.

The present studies were directed to examine the effects of beta-adrenergic and cholinergic stimulation on gastrin release and to assess the potential role of gastrin-releasing peptide in exerting these effects, utilizing incubated rat antral mucosa. Rat antral mucosa was incubated at 37 degrees C in Krebs-Henseleit bicarbonate buffer, pH 7.4, continuously gassed with 95% O2-5% CO2. After 1 h media were sampled for radioimmunoassay measurement of gastrin content. Inclusion of carbachol (2.5 X 10(-6) M) in culture medium increased medium gastrin concentration by 106 +/- 28% (P less than 0.01); addition of specific antibodies to gastrin-releasing peptide to the culture medium did not affect carbachol-stimulated gastrin release. Inclusion of isoproterenol (10(-9) M) in culture medium did not affect somatostatin release into the medium, but increased medium gastrin by 234 +/- 24% (P less than 0.001). However, in contrast to carbachol, addition of antibodies to gastrin-releasing peptide to culture medium decreased isoproterenol-stimulated gastrin release by 67 +/- 9% (P less than 0.001). Results of these studies indicate that, under the conditions of these experiments, beta-adrenergic, but not muscarinic, stimulation of gastrin release may be mediated, at least in part, through gastrin-releasing peptide.

A model was designed to permit sampling of portal venous blood in nonanesthetized dogs. Five mongrel dogs were prepared with indwelling portal venous catheters and gastric fistulas. After a minimum recovery period of 7 days, a 10 percent peptone meal was infused into the stomach. Portal and peripheral venous sera were obtained in the basal state and at various time points after intragastric peptone infusion. Serum gastrin concentrations were later measured by radioimmunoassay. Mean basal gastrin from portal and peripheral venous sera were 17 +/- 5 and 13 +/- 2 pg/ml, respectively. After peptone infusion, a biphasic gastrin response was observed. The first peak in portal venous serum occurred at 2 minutes, increasing to 49 +/- 20 pg/ml, while in the peripheral venous serum, the initial peak occurred at 4 minutes to 33 +/- 4 pg/ml. The second peak component occurred at 30 minutes in both circulations, increasing to 35 +/- 14 pg/ml in portal venous serum and to 29 +/- 8 pg/ml in peripheral venous serum. The results of this study (1) demonstrate that the release of gastrin after a peptone meal in the dog is prompt and biphasic, and (2) provide an effective method for obtaining simultaneous portal and peripheral venous blood for measurement of gastrointestinal peptides in alert, nonanesthesized dogs.

Organ culture was used to compare gastrin and somatostatin release from cultured antral mucosa obtained from duodenal ulcer and non-ulcer (control) subjects. In response to dibutyryl cyclic AMP (DBCAMP) cultured antral mucosal explants from patients with a history of duodenal ulcer released a greater proportion of antral gastrin into the medium than did antral mucosal explants from non-ulcer subjects. Somatostatin release from antral mucosa from duodenal ulcer patients was substantially less than somatostatin released by antral explants from non-ulcer subjects. In the non-ulcer subjects there was a direct positive correlation between the amounts of antral somatostatin and gastrin released into the culture medium (r = 0.64, less than p 0.01). In the duodenal ulcer patients, however, there was no correlation between gastrin release and somatostatin release from antral mucosa ( r = 0.09; p greater than 0.2). Results of these studies identify enhanced gastrin release in response to stimulation and decreased release of somatostatin from antral mucosa of duodenal ulcer patients. These alterations in paracrine relationships of antral somatostatin and gastrin in duodenal ulcer subjects may contribute, at least in part, to the pathogenesis of duodenal ulcer disease.

The presence and development of immunoreactive gastrin (IRGa) in the fetal and neonatal pancreas and pyloric antrum of the rat were studied. IRGa appeared in both organs at least as early as the 16th day of fetal life. Antral IRGa increased rapidly and continuously in the neonatal period, while pancreatic IRGa concentration increased and was maintained at a relatively constant level from days 5 to 35. Monolayer cell cultures of the neonatal rat pancreas were used to evaluate the role of cyclic AMP mediated release of gastrin. The addition of N6,O2'-dibutyryl cyclic AMP (4 mM) or theophylline (4 mM) to the culture medium induced significant release of gastrin. The stimulation of adenylate cyclase with cholera toxin (10 ng/ml) also resulted in significant gastrin release. Long-term cultures (18-24 days) were shown to release gastrin continuously at a relatively constant rate. The cellular localization of pancreatic gastrin in 7-day-old cultures was performed by immunological techniques, using fluorescein-labeled antibodies to gastrin. The gastrin-containing cells were located at the periphery of most of the endocrine cell clusters. Immunofluorescence techniques for insulin and glucagon also showed that the alpha cells had a similar peripheral distribution, although they were more frequent in number. In contrast, insulin-containing cells were numerous and were present in all areas of the endocrine cell clusters. The studies support the following conclusions: a) Gastrin is present in the rat pancreas, even as early as late fetal life; b) Gastrin-producing cells are present and functionally competent in monolayer cell cultures of the neonatal rat pancreas for prolonged periods of time (24 days); c) Gastrin is released from these cells when intracellular levels of cyclic AMP are increased; d) By immunofluorescence methods, the gastrin-producing cells in pancreatic cell cultures are found to be located at the periphery of the endocrine cell clusters.

Tissue culture methods were used to study the gastrin-producing cells isolated from the pyloric antral mucosa of rats. Cultures were maintained for up to 7 days. Gastrin cells were identified by means of immunofluorescent and unlabeled antibody-enzyme techniques. The tissue culture medium was monitored for basal gastrin secretion. In addition, stimulation of gastrin release was achieved by the use of dibutyryl cyclic-AMP and theophylline. This is the first report of the successful application of tissue culture methods to the functional study of antral gastrin cells. The procedure has proven to be useful in assessing the mechanisms of gastrin secretion.

Specific binding of radiolabeled gastrin by gastric mucosal cells prepared from guinea pigs was detected and examined. Specific cell binding of gastrin was found to be both pH and temperature dependent. Maximum binding of radiolabeled gastrin by gastric mucosal cells was demonstrated at pH 7.4 and at 4 degrees C. Substantial degradation of 125I-gastrin occurred during incubation with gastric mucosal cells. Gastrin degradation was detected both by loss of immunological reactivity with antibodies to gastrin and by abolition of subsequent specific binding after prior incubation with gastric mucosal cells. Degradation of gastrin was most marked with incubations conducted at pH 7.4 and at low pH (pH 2.0), suggesting the activities of at least two gastrin-degrading enzyme systems in the gastric mucosal cell preparation.

Peptone perfusion of the excluded duodenum in dogs is associated with an increase in lower esophageal sphincter pressure (LESP). This study investigates the role of cholinergic, adrenergic, and hormonal mediators in the response of the LES to intraduodenal peptone infusion. Adult dogs underwent duodenal exclusion via a Roux-en-Y pylorojejunostomy with formation of a mucocutaneous fistula. Manometric measurements of LESP and radioimmunoassay determinations of gastrin and pancreatic polypeptide (PP) blood levels were made at rest and at 15-min intervals following peptone infusion of the excluded duodenum. In control experiments, peptone infusion resulted in an increase in mean LESP at all time intervals (P less than 0.05). PP blood levels increased significantly, while gastrin levels remained unchanged. Both truncal vagotomy and pretreatment with atropine blocked the changes in LESP. PP release in response to peptone was accentuated in vagotomized dogs, while atropine suppressed the release of PP following peptone infusion. Treatment with 6-hydroxydopamine did not affect the increase in either LESP or PP blood levels observed in controls. Intravenous somatostatin suppressed the release of PP following intraduodenal peptone, but did not block the lower esophageal sphincter response. This data indicates that the increase in LESP seen following intraduodenal peptone infusion is centrally mediated and dependent on vagal innervation and cholinergic neurotransmission.

The effects of the microtubule stabilizing agent, deuterium oxide, on in vitro rat antral gastrin release were examined under basal conditions and during stimulation with isobutyl methylxanthine and bombesin plus isobutyl methylxanthine. Basal gastrin release from antral mucosal fragments was unaffected by increasing media concentration of deuterium oxide (12.5 to 75% v/v) during 1 h incubations. Gastrin release stimulated by isobutyl methylxanthine (0.1 mM), a potent inhibitor of phosphodiesterase activity, was inhibited completely by 12.5% deuterium oxide. Bombesin (1 X 10(-8) M) in the presence of IBMX (0.1 mM) stimulated gastrin release (29.7 +/- 1.9% of total gastrin). This was significantly greater than gastrin released under control conditions and with IBMX alone: 12.0 +/- 1.1 (P less than 0.001) and 20.2 +/- 2.6% of total gastrin (P less than 0.02), respectively. Partial inhibition of bombesin-IBMX stimulated gastrin release was achieved with 12.5% and 25% deuterium oxide and stimulation of gastrin release was inhibited completely by 50% deuterium oxide. In contrast to these results, gastrin release stimulated by the calcium ionophore A23187 was not inhibited by 50% deuterium oxide. Additional studies were performed to assess reversibility of the effects of deuterium oxide on stimulated gastrin release. Antral tissue exposed to initial culture medium containing deuterium oxide (50%) and bombesin-IBMX for 60 min was exchanged for medium without deuterium oxide. Restimulation of antral tissue during the second hour of culture resulted in gastrin release that was comparable to that observed in cultures not exposed to deuterium oxide during the first hour of culture. Reversibility of the effects of deuterium oxide suggest that a functional alteration in microtubular function is restored by removal of heavy water from the culture medium. Results of these experiments indicate that deuterium oxide is capable of inhibiting gastrin release stimulated by the peptide hormone bombesin and by the phosphodiesterase inhibitor isobutyl methylxanthine. Furthermore, these results suggest that increased levels of intracellular calcium achieved by the action of ionophore A23187 prevent microtubular stabilization by deuterium oxide.