Effects of truncal vagotomy and antrectomy on bombesin-stimulated pancreatic secretion,release of gastrin,and pancreatic polypeptide in the anesthetized dog

The short-term effects of truncal vagotomy and antrectomy on bombesin-stimulated pancreatic secretion and release of gastrin and pancreatic polypeptide (PP) were studied in 18 anesthetized dogs. Together with an intravenous infusion of secretin (250 ng/kg/hr) bombesin (500 ng/kg/hr) was given before and after truncal vagotomy, antrectomy, and sham operation (N=6 dogs per group). Peak incremental pancreatic protein output in procedures (tachyphylaxis). Neither truncal vagotomy nor antrectomy significantly altered the pancreatic protein response to bombesin when compared with sham operation. Bombesin produced a mean 1-hr increase over basal of 196 pM for gastrin, which was abolished by antrectomy but not appreciably affected by truncal vagotomy and sham operation. The mean 1-hr increment (207 pM) for PP in response to bombesin was not changed by truncal vagotomy, antrectomy, and sham operation. This study shows in the anesthetized dog that exogenous bombesin stimulates release of PP as well as gastrin; that the release of gastrin by bombesin is not vagally dependent; that neither truncal vagotomy nor antrectomy alter the release of PP by bombesin; and that the action of bombesin on pancreatic protein secretion does not depend on release of gastrin or on intact vagal nerves.Parts of this paper have been presented at the 12th European Pancreatic Club Meeting, Copenhagen, Denmark, October 11–13, 1979, and at the 3rd International Symposium on Gastrointestinal Hormones, Cambridge, England, September 15–18, 1980.     

Effects of exogenous and endogenous bombesin on gastrin secretion from rat antral mucosa in tissue culture

Effects of exogenous and endogenous bombesin on gastrin secretion were examined using rat antral mucosa in tissue culture. Gastrin secretion was significantly stimulated by exogenous bombesin at a dose of 10(-8) M. Atropine 10(-6) M, which abolished the action of the cholinergic agent carbachol to stimulate gastrin secretion, had no effect on bombesin-stimulated gastrin secretion. In addition, gastrin secretion was significantly inhibited by anti-bombesin antiserum used to block the effect of endogenous bombesin by immunoneutralization. These findings suggest that the stimulation of gastrin secretion by bombesin does not involve cholinergic neural pathways and that endogenous bombesin exerts a continuous stimulation on gastrin secretion in the basal state.     

Neural pathways for the release of gastrin,cholecystokinin, and pancreatic polypeptide after a meal in dogs

We have measured gastrin, cholecystokinin (CCK), and pancreatic polypeptide (PP) release after a meal in normal dogs under basal conditions and during atropine infusion, and after various neural sections. Denervation of the gastric antrum (antral vagotomy) abolished the early part of the gastrin response to food. Truncal vagotomy, celiac ganglionectomy, and atropine reduced the early release of CCK, which occurred before the start of gastric emptying, suggesting that a neural, cholinergic mechanism may release CCK immediately after a meal. PP release was abolished by truncal vagotomy, and also by antral vagotomy. As no direct pathways are known between the antrum and the pancreas, this suggests either that antral afferents are essential for this response or that vagally mediated hormone release from the antrum mediates PP release.     

The role of gastrointestinal peptides on pancreatic secretion in response to different stimulants in conscious rats

Summary Effects of intragastric food, intraduodenal amino acids, and intravenously administered bombesin and gastrin-releasing peptide (GRP) were examined in conscious rats with pancreatic fistula in terms of responses of exocrine pancreatic secretion, plasma levels gastrin, and cholecystokinin (CCK). Pancreatic juice and blood samples were collected at regular intervals before and after the stimuli. Intragastric food increased pancreatic secretion and plasma levels of gastrin and CCK. Intraduodenal infusion of amino acids had no effect on pancreatic secretion and plasma levels of gastrin and CCK. Intravenous infusion of bombesin at 1 μg/kg/h induced significant increases in pancreatic volume and protein outputs, but had no effect on plasma levels of gastrin and CCK. Bombesin infusion at 10 μg/kg/h resulted in significant increases in pancreatic volume and protein outputs as well as plasma gastrin levels, but had no effect on plasma CCK levels. Intravenous infusion of GRP induced increases in pancreatic volume and protein outputs and plasma gastrin levels, but had no effect on CCK levels. Antrectomy resulted in significant decreases in basal levels of plasma gastrin. GRP-stimulated pancreatic volume and protein outputs were not significantly changed by antrectomy. In rats that underwent antrectomy, GRP infusion significantly increased pancreatic volume and protein outputs, but had no effect on plasma levels of gastrin and CCK. Food-stimulated pancreatic secretion and plasma levels of gastrointestinal peptides of rats were similar to other species, but amino acids, bombesin, or GRP may not be the stimulants for CCK release in rats. The stimuli that release CCK from duodenal mucosa probably varies among species.     

The cephalogastric phase of the pancreatic response to food in the dog

We studied post-meal pancreatic secretion and gastrin release in conscious dogs with duodenal Thomas cannulas. Normal dogs were tested in physiological conditions and with an i.v. infusion of atropine 20 micrograms/kg/h or secretin 0.5 CU/kg/h. The responses were also studied after antral and truncal vagotomy. In the early phase (0-20 min) of the response, before gastric emptying started, antral vagotomy reduced fluid and protein outputs, and truncal vagotomy reduced them still more. Atropine reduced only the protein response. Gastrin release reached a peak after 20-25 min. After antral and truncal vagotomy, gastrin release was reduced within 10 min after the meal. Late-phase (greater than 20 min) pancreatic secretion depended on the presence of chyme in the duodenum. The effects of atropine and antral vagotomy in the cephalogastric phase could be explained by antropancreatic reflexes stimulating fluid secretion (atropine-resistant pathway) and protein output (atropine-sensitive pathway).     

Stimulation of gastrin release and gastric secretion: effect of bombesin and a nonapeptide in fistula dogs with and without fundic vagotomy.

Bombesin and a synthetic bombesin nonapeptide were studied by intravenous infusion at a dose of 0.5 microgram.kg-1.h-1 for 4 h in 7 dogs with esophagostomy and gastric fistula. In 3 of the dogs who had highly selective (fundic) vagotomy, mean integrated gastrin output over 4 h was double that in the 4 dogs with vagi intact during both nonapeptide (1,554 vs. 700 pg.ml-1.4 h-1) and bombesin infusion (2,442 vs. 1,440 pg.ml-1.4 h-1). Peak concentrations of serum gastrin reached during bombesin (490 +/- 100 vs. 320 +/- 90) were higher than those during nonapeptide infusion (270 +/- 40 vs. 160 +/- 28 pg/ml) in the vagotomized and intact dogs, respectively. The difference between vagotomized and vagally intact dogs suggests that the fundic vagotomy removed an inhibitor of gastrin release from the innervated antrum. Despite these differences in gastrin release, gastric acid output with the two peptides was the same (49--52 mEq/4 h) whether the fundus was denervated or innervated. This suggests that bombesin may stimulate gastric acid secretion by the release of an additional secretagogue which is not measured by the gastrin assay. Neither of the two inhibitors of gastrin release--antral acidification to pH 1.4 or less or atropine (100 microgram/kg)-- inhibited gastrin release by bombesin, even though the atropine reduced acid output by 80%. Bombesin is a potent gastric stimulus whose action is only partly explained by the measured gastrin release.     

Effect of truncal vagotomy on functional and morphological changes produced by duodenogastric reflux

The effects of truncal vagotomy on the functional and morphological changes produced by duodenogastric reflux have been studied in the dog. Duodenogastric reflux caused progressive damage to gastric mucosa, hypersecretion of acid to pentagastrin, and a hypergastrinemic response to a standard meal. Truncal vagotomy barely altered the mucosal changes produced by reflux, but it did prevent antral gland hyperplasia and reduced the acid gastrin secretory responses. These findings are clinically reassuring in that vagotomy effectively prevented the hypersecretory state produced by duodenogastric reflux.     

Neural and paracrine regulation of gastrin release using rat antral mucosa in tissue culture--the effect of carbachol, bombesin, and anti-somatostatin antibody on gastrin release

Gastrin release was significantly stimulated by the cholinergic agent carbachol at doses of 10(-4) M, 10(-5) M, and 10(-6) M. Peak stimulation was observed at 10(-5) M. Gastrin release was also significantly stimulated by bombesin at a dose of 10(-8) M, and 10(-6) M atropine which abolished the effect of carbachol in stimulating gastrin release had no effect on the bombesin-stimulated gastrin release. In addition, anti-somatostatin antiserum significantly stimulated gastrin release. These findings suggest that gastrin release is regulated by cholinergic and noncholinergic neurons the latter being thought to be a bombesin-containing neuron, and that antral somatostatin exerts a continuous restraint on gastrin release by the paracrine mechanism.     

Effects of bombesin on the release of glycine-extended progastrin (gastrin G) in rat antral tissue culture

Recently, glycine-extended processing intermediates of progastrin were identified in porcine stomach using a radioimmunoassay with conventional polyclonal antisera developed against a synthetic peptide analogue for progastrin processing intermediates, gastrin 6-G(Tyr-Gly-Trp-Met-Asp-Phe-Gly). We developed monoclonal antibodies specific for glycine-extended processing intermediates of progastrin (gastrin G). Monoclonal antibody 109-21 appeared to require the carboxyl-terminal pentapeptide structure of gastrin 6-G for maximal binding. Cross-reactivities of 109-21 against gastrin 17 I, gastrin 17 II, cholecystokinin-octapeptide, des(SO3) cholecystokinin-octapeptide, and gastrin 6-G-R-R were respectively 1%, less than 0.1%, less than 0.1%, 0.1%, and 0.5%. With this monoclonal antibody and a polyclonal gastrin antibody we examined the concentrations of gastrin and gastrin G in tissue and the effects of bombesin on the release of gastrin and gastrin G from rat antral mucosa in tissue culture. The gastrin G to gastrin ratio was 2.2 in rat antral mucosa and 0.66 in rat duodenal mucosa. In tissue culture, bombesin significantly stimulated gastrin and gastrin-G secretion at doses of 10(-8) and 3 X 10(-8) M. Atropine (10(-6) M) abolished the actions of carbachol to stimulate gastrin and gastrin-G secretion but had no effect on bombesin-stimulated gastrin and gastrin-G secretion. These results suggest that gastrin G is cosecreted with gastrin in response to carbachol and bombesin, and the stimulation of gastrin and gastrin-G secretion by bombesin does not involve cholinergic neural pathways and may reflect a direct action on gastrin cells.     

The vagus exerts trophic control of the stomach in the rat

Bilateral subdiaphragmatic truncal vagotomy results in great functional changes in the stomach although the changes in the gastric mucosal architecture are small. A trophic effect of the vagus on the stomach is revealed after unilateral vagal sectioning, taking advantage of the fact that, in the rat, each vagal trunk innervates only one side of the stomach, and that denervation of one side does not impair the functional capacity of the other. The denervated side of the stomach displayed atrophy that was reflected in reduced weight and height of the oxyntic mucosa and a reduced density of argyrophil cells. The lack of atrophy after bilateral vagotomy can be explained by counteracting forces, in that the subsequent rise in gastrin secretion (due to lack of acid feedback inhibition of gastrin release) probably masks antitrophic effects of the vagotomy per se. Interestingly, the number of somatostatin cells in the oxyntic mucosa was not reduced after unilateral vagotomy, nor was the weight of the antral mucosa or the density of enterochromaffin and gastrin cells in the antrum on the denervated side.     

Effect of Platelet-Activating Factor on Gastrin Release from Cultured Rabbit G-Cells

Gastric infection with Helicobacter pylori is associated with hypergastrinemia. Platelet activating factor (PAF) is produced in H. pylori-infected mucosa. The effects of PAF on gastrin release from cultured antral rabbit G cells were examined. Rabbit antral G-cells were obtained by collagenase-EDTA digestion and enriched by centrifugal elutriation. After 40 hr in culture, gastrin release in response to PAF was assessed. PAF stimulated gastrin release in a dose-dependent manner. A maximal release of 67% above basal was seen with PAF at 100 nM. PAF also enhanced the gastrin release stimulated by forskolin and bombesin. PAF-stimulated gastrin release was abolished by a PAF-receptor antagonist. Gastrin release stimulated by PAF was abolished by chelation of intra- or extracellular calcium or the L-type calcium channel inhibitor verapamil as well as by the protein kinase C inhibitor chelerythrine. Platelet-activating factor may contribute to the hypergastrinemia of H. pylori infection by stimulating gastrin release from G cells. PAF-stimulated gastrin release involves influx of extracellular calcium via L-type channels and activation of protein kinase C.     

Response of Heidenhain Pouch to Histamine,Gastrin and Feeding before and after Truncal Vagotomy in Dogs

Dogs with both gastric fistulas of the main stomach and Heidenhain pouches were studied before and after transthoracic truncal vagotomy. Confirming earlier studies in dogs with gastric fistulas alone, truncal vagotomy abolished the acid secretion in response to 2-deoxy-D-glucose (2-DG) and depressed the response to submaximal doses of exogenous gastrin or histamine but did not alter the maximal responses to gastrin or histamine. Effects of truncal vagotomy on acid secretion from the Heidenhain pouches: a) response to 2-DG with the gastric fistulas open was abolished, b) submaximal, but not maximal, responses to histamine were decreased, c) submaximal and maximal responses to exogenous gastrin were markedly increased, and d) response to feeding was markedly increased.     

The role of the antrum and the vagus nerve in the metabolism of histamine in the human gastric mucosa.

The effects of antrectomy and proximal gastric vagotomy on the metabolism of histamine in the human gastric mucosa were studied in the basal state and during pentagastrin stimulation in patients with duodenal or gastric ulcer disease. Mucosal biopsy specimens were taken from the antral and oxyntic gland areas, whereafter histamine content, histidine decarboxylase activity, and histamine methyltransferase activity were simultaneously assayed. Vagotomy was followed by a decrease in the acid secretory capacity and an increase in basal serum gastrin levels. Histamine content of the oxyntic mucosa increased after vagotomy, but the ability of pentagastrin to form new amounts of the amine was impaired. Antrectomy caused a decrease in acid secretion and a fall in gastrin concentrations. Basal histamine content and rate of amine formation in the remaining oxyntic mucosa were unaffected by antrectomy. Antrectomy impaired the ability of pentagastrin to release histamine. Histamine methyltransferase was not affected by pentagastrin, vagotomy, or antrectomy. In conclusion, both antral gastrin and the vagus nerve seem to exert a regulatory influence on the metabolism of histamine in the human oxyntic mucosa. The withdrawal of these factors either causes impaired ability of pentagastrin to release histamine from its storage site or counteracts the ability of pentagastrin to accelerate histamine synthesis.     

Effect of bombesin on extragastric gastrin in man

The effect of a protein test meal and a bombesin infusion on extragastric gastrin levels was studied in patients with truncal vagotomy, antrectomy, and gastroduodenostomy or gastrojejunostomy and in patients with total gastrectomy. In patients with vagotomy, antrectomy, and gastroduodenostomy and in patients with total gastrectomy the gastrin levels were raised by 33% and 35%, respectively, from basal after test meal, while during BBS infusion gastrin values decreased by 25% and 30%, respectively, from basal. In patients with vagotomy, antrectomy, and gastrojejunostomy, test meal and BBS infusion did not significantly alter basal gastrin values. It is concluded that BBS does not stimulate extragastric gastrin.     

Role of gastrin in bombesin-stimulated somatostatin release

The intermediary pathways in the bombesin-induced somatostatin release were examined in isolated perfused rat stomach obtained from male rats that were fasted overnight. The stomachs were perfused by way of the celiac artery. On coinfusion of 1.0 mumol/L tetrodotoxin and 1 nmol/L bombesin, a significant depression in release of somatostatin was observed compared with that observed with bombesin alone. The 5-minute integrated somatostatin response after treatment with tetrodotoxin and bombesin was 173% +/- 14% of basal, which was significantly lower than that observed with bombesin alone (394% +/- 59% of basal, P less than 0.05) but significantly higher than that observed with medium-199 alone (95% +/- 7% of basal, P less than 0.05); this indicated that approximately 70% of the bombesin-stimulated somatostatin release was indirectly mediated through neural pathways, while a significant (approximately 30%) segment of it was mediated by nonneural mechanisms. To test if the 30% somatostatin release was secondary to gastrin release in response to bombesin, gastrin antiserum and bombesin (1 nmol/L) were coadministrated in the presence or absence of tetrodotoxin (1 mumol/L). Gastrin antiserum alone did not significantly affect basal release of somatostatin but caused a significant inhibition (approximately 23%) of bombesin-provoked somatostatin release. Coadministration of gastrin antiserum and tetrodotoxin attenuated bombesin-stimulated somatostatin release. Gastrin (1 mumol/L) alone significantly stimulated somatostatin release (150% +/- 10% of basal), which was completely attenuated in the presence of gastrin antiserum. Tetrodotoxin did not affect bombesin-elicited gastrin release, confirming that bombesin-stimulated gastrin release was directly mediated. To determine the nature of the neural pathways mediating the bombesin-induced somatostatin release, atropine (100 nmol/L) was used. Atropine inhibited bombesin-induced somatostatin release to the same extent as tetrodotoxin, indicating that cholinergic pathways mediated bombesin-induced somatostatin release. These results show that almost all the somatostatin response to bombesin is indirectly mediated, and is composed of a major neural (cholinergic) and a minor nonneural pathway. The nonneural mechanism appears to be contributed primarily by gastrin released in response to bombesin, which apparently has a short paracrine positive feedback effect on somatostatin release.     

The effect of chemical sympathectomy on the cell kinetics of gastric mucosa in golden hamsters

The effects of chemical sympathectomy on the differentiation of the generative cells, superficial epithelial cells and gastrin cells of the gastric mucosa of hamster were examined by 3H-thymidine autoradiography. The labeling indices of the generative cell zone in the gastric mucosa and antral gastrin cells showed a transient significant decrease after chemical sympathectomy, and then they were gradually restore with time. After 4 weeks onward, the labeling indices of the generative cells showed a slightly low value compared with those in controls. The renewal of superficial epithelial cells and gastrin cells was examined in the hamster sympathectomized for 4 weeks. The time required for the differentiation to PAS positive superficial epithelial cells or gastrin cells had a tendency to elogate after chemical sympathectomy. These results suggest that chemical sympathectomy played an inhibitive action on the proliferation and the differentiation of gastric mucosa.     

Gastrin secretion from human antral G cells in culture

Receptor-dependent and -independent regulation of gastrin secretion from cultured human antral G cells was investigated. Human antral mucosal cell preparations that were enriched for G cells were obtained by sequential incubations with collagenase and ethylenediaminetetraacetic acid, centrifugal elutriation, and short-term culture. After a 2-day incubation period, gastrin- and somatostatin-containing cells accounted for 15% and 5%, respectively, of the total adhered-cell population. Forskolin, A23187, and beta-phorbol 12 myristate 13-acetate stimulated basal gastrin secretion from cultured human G cells in a concentration-dependent fashion. These results indicate that gastrin release could be mediated by elevations in cytosolic cyclic adenosine monophosphate levels, calcium influx, or activation of protein kinase C. A direct stimulatory role for bombesin- and gastrin-releasing peptide was supported by experiments showing concentration-dependent enhancement of gastrin release by bombesin from 0.01 fmol/L to 10 nmol/L. The putative bombesin antagonist [Leu13-psi-CH2NH-Leu14] bombesin augmented basal gastrin levels by itself and produced weak inhibition of bombesin-induced gastrin secretion from human antral G cells. Somatostatin potently suppressed forskolin- and bombesin-mediated gastrin release but did not significantly alter basal gastrin levels. These results suggest that bombesin and somatostatin directly activate and inhibit G-cell function via specific and sensitive receptors. Furthermore, the adenylate cyclase and phosphatidyl inositide second messenger systems seem to be intracellular mediators of gastrin secretion from human antral G cells.     

Effect of different denervation procedures on catecholamines in the gut

Sympathectomy has been used to study the role of the sympathetic nervous system in the control of gastric acid secretion. Conflicting results may reflect differences in the sympathectomy procedures used. In a previous study we showed a reduction of catecholamines by more than 90% in the gut wall of the rat after surgical upper abdominal sympathectomy. The aim of the present investigation was to ascertain whether chemical sympathectomy was equally effective and whether total denervation, including combined chemical and surgical sympathectomy together with bilateral truncal vagotomy, would lower the catecholamine levels further. The results showed that chemical sympathectomy reduced noradrenaline levels in fundus (oxyntic) and antrum mucosa to levels similar to those after surgical sympathectomy (less than 5%), but the reduction was less pronounced in the muscle layer of the fundus and antrum and in the pancreas and spleen. Combined surgical and chemical sympathectomy did not reduce noradrenaline more effectively than surgical sympathectomy alone. Vagotomy reduced catecholamines in the stomach by about 50%; in extragastric tissues vagotomy was without effect. Total denervation, including combined surgical and chemical sympathectomy plus vagotomy, did not reduce noradrenaline levels more than surgical sympathectomy alone, suggesting that the proportion of adrenergic fibers that derive from the vagus is quantitatively insignificant but that the vagus exerts a local control of the sympathetic stores of gastric catecholamines.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of antisomatostatin gamma-globulin on gastrin release in rats

In order to determine the mechanism of endogenous gastric somatostatin in the regulation of gastrin release, antisomatostatin rabbit gamma-globulin was administered in vivo and in vitro in the rat. First, in rats anesthetized by chloral hydrate, intravenous injection of 1 ml antisomatostatin rabbit gamma-globulin had no significant effect on plasma gastrin levels. Second, basal gastrin release from the isolated perfused rat stomach was not affected by the administration of antisomatostatin rabbit gamma-globulin (1:99 and 1:1 dilutions). Third, the addition of antisomatostatin rabbit gamma-globulin (1:99) to incubated rat antral mucosa, however, significantly increased the basal gastrin release. From these results, it is concluded that antral somatostatin exerts its inhibitory effect on basal gastrin release mainly not through the circulation but via paracrine pathways.     

Involvement of capsaicin-sensitive neurons in gastrin release provoked by intragastric administration of bile salts in the rat

To clarify the mechanism of gastrin release provoked by the reflux of bile juice into the stomach, we studied the effects of tetrodotoxin (0.08 mg/kg), atropine sulfate (0.5 mg/kg), truncal vagotomy, and chemical denervation of afferent sensory neurons with capsaicin (100 mg/kg) on gastrin release induced by bile salts in the rat (n=6 per group). Sodium taurocholate and deoxycholate (>2.5 mM) significantly increased the serum levels of gastrin. However, sodium tauroursodeoxycholate had no effect. The levels of serum gastrin before and 1 h after administration of 2.5 mM sodium taurocholate were 94.6±10.7 and 211.0±21.1 pg/ml, respectively. Tetrodotoxin and atropine sulfate completely inhibited this sodium taurocholate inducedgastrin increase, while truncal vagotomy was without effect. Capsaicin markedly reduced the increasing effects of sodium taurocholate. These findings suggested that the neuronal pathways involved in gastrin release are probably an intragastric local circuit originating from capsaicin-sensitive afferent sensory neurons and terminating in muscarinic receptors in the postsynaptic efferent cholinergic neuron system.