Effect of long-term cimetidine on gastric acid secretion, serum gastrin, and gastric emptying.

Gastric acid secretion, gastric emptying, fasting serum gastrin and the serum gastrin response to a meal were measured in duodenal ulcer patients before, and at least five days after completing prolonged treatment with cimetidine (1 or 2 g/day for four or eight weeks followed by 600 mg twice daily for six months). Fasting serum gastrin and the gastrin response were also measured during treatment. Compared with pretreatment values, fasting serum gastrin concentrations were raised both during and five to 31 days after stopping treatment (P less than or equal to 0.02). The integrated gastrin response and the rate of gastric emptying of the solid component of the meal were increased during treatment (P less than 0.001 and P less than 0.002 respectively) but returned to pretreatment levels after stopping therapy. No significant changes were observed in the basal or maximal acid outputs or the rate of emptying of the liquid component of the meal. The results imply that the hypergastrinaemia associated with long-term cimetidine therapy does not result in increased gastric acid secretion.     

Effect of optimum therapeutic dose of poldine on acid secretion, gastric acidity, gastric emptying, and serum gastrin concentration after a protein meal.

An oral optimum therapeutic dose of poldine was established in 5 normal subjects. Acid secretion in response to a protein meal was measured for 3 hr by continuous intragastric titration with sodium bicarbonate. Poldine 30 min before the meal reduced food-stimulated acid secretion from zero to 60% in the 5 subjects (average inhibition 32%). Poldine inhibited histamine-stimulated acid secretion to approximately the same extent. In separate experiments, gastric acidity after the meal was allowed to seek its natural level (i.e., there was notitration with bicarbonate). Poldine reduced average hydrogen concentration of the gastric contents by 85 to 50% from 1.5 to 3 hr after the meal. Since poldine did not alter the volume or the buffer content of the stomach, poldine inhibition of gastric acidity is due entirely to reduction of acid secretion and not to delayed emptying of food buffer. Poldine had no consistent effect on serum gastrin concentration after the meal when pH was maintained at a constant level by titration with bicarbonate; therefore, poldine inhibition of acid secretion is not mediated by a reduction of serum gastrin concentration.     

Postprandial Pancreatic Secretion and Plasma Hormones in Dogs with Pancreatic Fistula

The responses of exocrine pancreas, plasma secretin, and gastrin to a test meal were studied in six dogs prepared with gastric and duodenal fistulas. The experiment was doubly repeated in each dog. Pancreatic juice was diverted to the exterior by direct cannulation into the major pancreatic duct. Volume, bicarbonate, and protein secretion of pancreatic juice were rapidly increased and then gradually reduced after the ingestion of the meal. Plasma secretin concentration reached a peak at 25 min after the ingestion of the meal and remained higher than the basal level for about 3 h. Plasma gastrin concentration rapidly reached a higher plateau which lasted for 40 min after the load of the test meal. A close correlation was observed between bicarbonate secretion and the increment in plasma secretin concentration and between protein secretion and the increment in plasma gastrin concentration. When pancreatic juice is diverted to the exterior, endogenously released secretin and gastrin appear to play an important role in postprandial pancreatic secretion.     

Mechanisms of the inhibitory action of prostaglandins on meal-induced gastric secretion

In dogs with gastric fistula and Heidenhain pouch (HP), 15(S)-15-methyl prostaglandin E2 methyl ester (PG-S) infused intravenously in graded doses (0.5--2.0 microgram/kg/h) inhibited dose-dependently, meal-induced acid secretion both from the vagally innervated main stomach and from the HP. This inhibition was associated with a marked reduction in mucosal blood flow but without significant change in the ratio of aminopyrine concentration in the gastric juice and blood plasma, indicating that the reduction in gastric microcirculation was probably secondary to the inhibition of gastric secretion. In dogs with special cannulae that allowed complete separation of the stomach and the intestine, PG-S caused stronger inhibition of gastric acid and serum gastrin responses to gastric and intestinal meals after application directly to the gastric mucosa, than following duodenal administration. PG-S applied topically to the HP mucosa also suppressed direct chemical stimulation of the HP by L-histidine meal. We conclude that PG-S exerts its inhibitory action on gastric secretion both by local contact with the mucosa via suppression on gastrin release from the antral G-cells and by direct inhibition of the secretory activity of the oxyntic glands.     

Gastrin and Acid Studies in the Pouch Dog

Serum gastrin and pouch acid secretion were measured in dogs with either innervated (Pavlov) or denervated (Heidenhain) pouches in the basal state and following a meat meal or insulin hypoglycaemia. The gastrin response to meat was consistently greater than to insulin hypoglycaemia and pouch acid output followed the changes in serum gastrin in both groups. These studies confirm that gastrin is the secretagogue responsible for acid secretion from a denervated pouch. They also indicate that intact vagal innervation is essential for the optimal effect of gastrin on acid secretion to be observed.     

The Effect of Propranolol on Insulin-stimulated Gastric Secretion in Dogs

The effect of beta-adrenergic blockade on the insulin hypoglycemia-induced gastric secretion was studied. Insulin-stimulated (0.15 IU/kg) gastric acid and pepsin output and serum gastrin were measured before and during beta-adrenergic blockade with propranolol (20 μg/kg/min intravenous infusion) in gastric fistula and Heidenhain pouch dogs. Insulin injection caused acid and pepsin secretion from the gastric fistula, and both acid and pepsin secretion was significantly increased during beta-adrenergic blockade. Significant gastrin release was observed after insulin stimulation. However, the insulin-induced gastrin release was unaltered by intravenous infusion of propranolol. The Heidenhain pouch did not show any secretion in these experiments. It is concluded that beta-adrenergic blockade augments the hypoglycemia-induced gastric secretion in dogs. Furthermore, it seems that this effect is not dependent on vagally released gastrin.     

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).     

Behaviour of acid secretion, gastrin release, serum pepsinogen I, and gastric emptying of liquids over six months from eradication of helicobacter pylori in duodenal ulcer patients. A controlled study.

The behaviour of basal and stimulated acid secretion, gastrin release, serum pepsinogen I, and gastric emptying of liquids was studied in 19 consecutive patients with Helicobacter pylori positive duodenal ulcer, over a follow up period of six months. Eleven patients were studied before and at three and six months after eradication with lansoprazole plus amoxicillin and tinidazole (case group), whereas the remainder, with persistent H pylori infection, were studied before and after three and six months from ulcer healing, thus constituting the control group. In the case group, three months after eradication, fasting serum pepsinogen I fell from (mean (SEM)) 91.9 (6.9) (pretreatment) to 72.2 (5.1) ng/l and the integrated gastrin response to a meal reduced from 11,470 (1174) (pretreatment) to 8130 (608) pg/ml/h (p < 0.05). Fasting serum gastrin concentrations and maximal acid output reduced significantly only six months after eradication. In contrast, no significant change of any of these measurements was seen in the control group either at three or six months from healing compared with the pretreatment values. Gastric emptying of liquids did not change over the entire period of follow up in both study groups. In conclusion, eradication of H pylori in duodenal ulcer patients is accompanied by a rapid fall in serum pepsinogen I and plasma gastrin concentrations, whereas a slight but significant reduction of maximal acid secretion takes place later on. In contrast, gastric emptying of liquids does not seem to be influenced by H pylori status.     

Serum gastrin response to food stimulation and gastric acid secretion in male patients with ileal resection.

Gastric acid secretion before and after stimulation with pentagastrin and serum gastrin response to a test meal were recorded in 9 male controls and in 7 male patients from whom more than 50 cm of the terminal ileum had been resected because of Crohn's disease. The mean gastric acid secretion before and after stimulation was not found to be significantly different in the two groups. The mean fasting serum gastrin concentration and the serum gastrin response in absolute values were not different in the two groups. The MAO-BAO/'integrated gastrin response' was higher (p less than 0.05), and the gastrin response in relation to fasting level was lower in the patients than in the controls (p less than 0.05). The results indicate that an increased parietal cell sensitivity to gastrin is present after ileal resection. The negative acid feed back mechanism, however, seems to be at work. Under physiological conditions, therefore, the increased sensitivity may not result in acid hypersecretion.     

Effect of calcitonin on gastric emptying in patients with an active duodenal ulcer.

In a double blind placebo controlled study the effect of calcitonin on gastric emptying and on serum concentrations of gastrin, insulin, glucose, calcium and phosphorus after a mixed solid-liquid meal was examined in eight patients with duodenal ulcer. Synthetic salmon calcitonin 415 pmol iv was given as a bolus followed by a 90 minute infusion to reach an overall dose of 62.25 pmol/kg. Gastric emptying of a radiolabelled meal was measured with a gamma camera. Calcitonin markedly delayed gastric emptying in all patients examined. The emptying index (Ix) decreased from 2.979 (0.397)/min after placebo to 0.896 (0.317)/min after calcitonin (p less than 0.001). Calcitonin did not affect significantly postprandial gastrin release: AUC0-90, 8768 (880) pg/l min (placebo) and 7807 (619) pg/l min (calcitonin). Postprandial insulin release was abolished by calcitonin -Auc0-90, 2258 (242) mU/l min (placebo) v 736 (131) mU/l min (calcitonin), p less than 0.001. Parallel to the suppression of insulin release was a steady increase in the serum glucose during calcitonin infusion, with the highest glucose concentration of 5.8 (0.53) mmol/l at the end of infusion of the hormone. Calcitonin did not change significantly serum calcium or phosphorus concentrations. A combination of a delaying effect on gastric emptying with the inhibition of gastric acid secretion elicited by calcitonin warrants further studies of calcinonin in the treatment of duodenal ulcer.     

Responses of serum gastrin and gastric acid output before and after bilioenteric by-pass in the dog and man.

Responses of serum gastrin and gastric acid output levels were studied in four dogs before and after a bilioenteric by-pass. Serum gastrin levels during bombesin infusion were measured in eight patients submitted to Roux-en-Y hepatocholangiojejunostomy. No change was observed in acid secretion from the main stomach or from the Heidenhain pouch in dogs following biliojejunostomy. The peak acid output, however, occurred significantly earlier after diversion of bile from the duodenum. Serum gastrin levels decreased significantly in dogs after bilioenteric by-pass and in the operated patients compared with normal subjects. The possible role played by bile in the release of duodenal gastrin is hypothesized.     

Chemicals bathing the oxyntic gland area stimulate acid secretion in dog.

Release of gastrin is the only recognized mechanism by which chemicals in the stomach stimulate acid secretion. We report here that dietary components coming in contact only with oxyntic gland mucosa stimulate near maximal acid secretion through a local, H-sensitive mechanism that does not involve gastrin. In 4 dogs with gastric fistula and Heidenhain pouch (HP), 10% liver extract, 10% peptone, 0.4 M glycine, or Tris buffer, as control, was instilled into the HP in volumes of 40, 80, or 160 ml every 30 min. Instilled solutions were adjusted to pH 8.0 and HP acid secretion was measured by titrating a sample of the fluid recovered from the HP back to pH 8.0 with 0.2 M NaOH. Instillation of liver extract into the HP stimulated acid secretion from the HP but caused no change in serum gastrin and no change in acid secretion from the gastric fistula. The maximal response to liver extract occurred with the largest volume instilled and was 80% of the maximal response to histamine and 188% of the maximal response to pentagastrin. Expressed as per cent of maximal response to histamine, the maximal response to Tris buffer was 8%, to peptone 44%, and to glycine 14%. Intact bovine serum albumin gave no response, but after digestion by pepsin it stimulated acid secretion moderately. At pH 2.0, liver extract caused no stimulation of acid secretion. The pH threshold was about 2.5, and at pH 4.5 acid secretion was 55% of the response at pH 8.0. The response to liver extract at pH 8.0 was only minimally decreased by topical lidocaine or by intravenous atropine or metiamide. Since atropine and metiamide almost totally abolish the acid response to food in the main stomach, but do not inhibit secretion of acid evoked by instilling liver extract into the HP, there is reason to doubt whether this new mechanism operates under physiological conditions.     

Stress-induced changes in gastric emptying, postprandial motility, and plasma gut hormone levels in dogs

The influence of acoustic stress on postprandial gastrointestinal motility, gastric emptying, and plasma gastrin, pancreatic polypeptide, motilin, and somatostatin was evaluated in conscious dogs. Six dogs were equipped with strain-gauge transducers and were exposed from 1-3 h after the meal to prerecorded music (80-90 dB broad frequency noise), which produced a significant (p less than or equal to 0.05) lengthening of the gastric (31.2%) and jejunal (37.0%) postprandial pattern. In 4 other dogs with gastric cannula, a 2-h session of acoustic stress beginning just after eating a radiolabeled standard meal induced a slowing of gastric emptying of both liquid (45.7%) and solid (47.1%) phases of the test meal when measured 0.5 h after feeding. In contrast, when measured 2 h after feeding, similar values of gastric emptying of liquids and solids were observed in stressed and control animals. Compared with controls, the postprandial increases of plasma gastrin and pancreatic polypeptide levels were significantly enhanced in stressed animals and occurred early (15 min after the meal). Although postprandial decrease in plasma motilin was unchanged by acoustic stress, the rise in plasma somatostatin level was significantly (p less than or equal to 0.05) prolonged in stressed dogs. These results indicate that acoustic stress affects gastric and intestinal postprandial motility in dogs, delaying the recovery of the migrating motor complex pattern, inducing a transient slowing of gastric emptying, and enhancing the feeding-induced release of gastrin, pancreatic polypeptide, and somatostatin. Such hormonal changes might be due to a direct effect of stress rather than being the consequence of acoustic stress-induced slowing of gastric emptying.     

The effect of cimetidine, a new histamine H2-receptor antagonist, on meal-stimulated acid secretion, serum gastrin, and gastric emptying in patients with duodenal ulcer.

Meal-stimulated acid secretion, measured by in vivo intragastric titration, was progressively inhibited by increasing oral doses of cimetidine (25 to 400 mg). Four hundred milligrams suppressed acid secretion by 73% for the first 3 hr after the meal, whereas it inhibited acid secretion by 94% during the 30-min period of maximal inhibition. The dose of cimetidine required to suppress acid secretion by 50% during the 30-min period of maximal inhibition was 25 mg. The duration of action of a 300-mg dose was at least 7 hr. Cimetidine was equally effective in inhibiting meal-stimulated acid secretion at two physiological intragastric pH levels (5.0 and 2.5). Cimetidine had no effect on serum gastrin concentration when intragastric pH was maintained at 5.0, but when pH was allowed to seek its own level, serum gastrin concentration was higher after cimetidine than after placebo. Cimetidine had no effect on gastric emptying. No side effects were noted in any patients.     

Effect of secretin on gastric function in normal subjects and in patients with duodenal ulcer.

The effect of constant intravenous infusion of secretin in doses of 0.25, 0.50, 1.50, and 3.0 mug per kg per hr on meal-stimulated acid secretion was measured in vitro titration to pH 5.0. The pattern and degree of secretin inhibition of food-stimulated acid secretion depended on when the secretin infusion was begun, the effect being more pronounced when the secretin was begun 1 hr before the test meal than when the meal and secretin infusions were begun simultaneously. Inhibition of acid secretion in normals was approximately the same as in 2 patients with pancreatic exocrine insufficiency who could secrete only small amounts of pancreatic bicarbonate in response to secretin. Secretin in dose of 0.25 and 0.5 mug per kg per hr inhibited acid secretion only slightly, whereas 3.0 mug per kg per hr completely stopped acid secretion. Inhibition of acid secretion by secretin was similar in controls and in patients with duodenal ulcer. Secretin also reduced the rise in serum gastrin concentration after the meal, and delayed gastric emptying; both responses were approximately the same in normals and in duodenal ulcer patients. Secretin inhibited basal gastric acid secretion but had no consistent effect on basal serum gastrin concentration.     

Pancreatic responses to endogenous and exogenous gastrin in the dog

Serum gastrin and pancreatic secretion were measured in conscious Thomas fistula dogs during infusion of increasing doses of porcine gastrin, against a background of secretin. Dose-response relationships were calculated for the effects of gastrin on pancreatic secretion. Gastrin release was also measured after a test meal and after vagal stimulation with 2-deoxyglucose. Peak serum gastrin levels after these stimuli were less than the serum gastrin level associated with the minimal effective dose of gastrin. From the dose-response relationship of serum gastrin and pancreatic protein output, it was possible to calculate the protein output corresponding to the peak gastrin levels after 2-deoxyglucose or a meal. These were equivalent to 20-30% of the observed protein response to these stimuli. We conclude that gastrin plays at most a small part in the stimulation of pancreatic secretion after a meal and in response to 2-deoxyglucose. We also found that truncal vagotomy reduces pancreatic sensitivity to gastrin.     

Effect of calcimimetic agent, KRN568, on gastrin secretion in healthy subjects

KRN568 is a calcimimetic compound which acts on the calcium sensing receptors (CaR) on the parathyroid gland to suppress secretion of PTH. A recent report has demonstrated that CaRs are expressed on cultured human antral gastrin cells and that gastrin secretion is stimulated by an increase in extracellular calcium level. However, the effect of KRN568 on serum gastrin levels has yet to be clinically assessed. We therefore studied the effect of this calcimimetic on gastrin secretion in healthy subjects enrolled in the phase 1 study for KRN568 currently carried out in Japan. Single doses of KRN568, ranging from 25 mg to 400 mg, were orally administered to 6 healthy male volunteers at fasting and after meal. One subject proved to be a poor metabolizer (PM) for this compound and showed more than 10-fold high concentrations of plasma KRN568 (fasting Cmax 90.8 and non-fasting 83.8 ng/ml) compared to the other 5 individuals (Cmax 6.5 +/- 2.2 and 7.4+/- 1.6 ng/ml, respectively). Plasma gastrin levels showed mild but apparent increase (from 30 to 125 pg/ml) in this particular subject, while there were no significant increases in the other five people (from 34 +/- 6 to 63 +/- 3 pg/ml) after oral administration of 400 mg KRN568 at fasting. In the PM, administration of KRN568 resulted in extraordinarily high serum drug levels associated with transient increase of gastrin levels. This observation suggested that calcium-induced stimulation of gastrin secretion in human was mediated by a mechanism involving CaR. Potential side effects related to the increased gastrin secretion may be warranted in the practical use of this compound.     

Gastrin response to meals of different composition in normal subjects.

The serum gastrin responses and the integrated gastrin responses to eating three meals of very different composition were studied in the same normal subjects on different days. Two meals, a milk meal of 500 ml, and a breakfast of eggs, toast, butter, marmalade, fruit juice and coffee, were eaten at breakfast time. The serum gastrin responses to these meals were compared and contrasted with the concentrations observed when the subjects fasted over the same time of day. A steak meal was eaten at lunch time. There were no significant differences between the mean serum gastrin concentrations to the three meals but each meal produced a significant increase in serum gastrin above fasting levels. When the prefeeding gastrin concentration was subtracted from the gastrin responses then the integrated responses to the steak meal were greater than those to either of the breakfast meals. Considerable variability in response to any one meal was observed within the group of subjects, but those subjects who produced high serum gastrin concentrations to one meal did so to the others. Conversely, at low response to one meal was reflected in low responses to the other two meals. Fasting serum gastrin concentration was correlated with the age of the subject. Repeatability of the response to one meal was tested in two subjects who ate the same meal on four separate occasions showing their responses to be repeatable.     

Effect of simulated intragastric haemorrhage on gastric acid secretion, gastric motility, and serum gastrin.

The majority of upper gastrointestinal bleeds stop spontaneously despite the low pH and proteolytic activity of gastric juice which inhibit coagulation and platelet aggregation. In order to investigate this paradox six healthy male volunteers received intragastric infusions of 160 ml autologous venous blood or 160 ml egg white acting as control in random order on separate days. Basal acid output was calculated before infusion, net acid secretion and gastric volume emptied were calculated after intragastric infusions. Serum gastrin concentrations were also measured before and after intragastric infusions and expressed as the integrated gastrin response. Basal acid output (mmol/h) was 4.7 (1.9) (mean (SEM)) before egg white infusion and 5.9 (2.6) before venous blood infusion. After egg white infusion net acid secretion (mmol/20 min) increased to 5.6 (3.1) compared with 2.3 (1.3) after venous blood infusion (p less than 0.05). The gastric volume emptied (ml/20 min) was less after venous blood infusion at 105 (28) compared with 321 (66) after egg white infusion (p less than 0.03). Integrated gastrin response was similar after venous blood and egg white infusion. When compared with an equivalent protein meal intragastric blood stimulates less acid secretion and delays gastric emptying. This effect may facilitate haemostasis after gastric bleeding.     

Neither cyclic AMP nor cyclic GMP appear to mediate antral gastrin release in the dog.

To evaluate whether cyclic nucleotides play a role as mediators in antral gastrin release, the following in vivo experiments were performed in dogs. An antral pouch was constructed and the rest of the stomach, the pancreas and small and large intestine were resected. A gastric artery supplying the pouch was cannulated, and after a basal period with saline infusion either dibutyryl cyclic 3',5'-adenosine monophosphate (cyclic AMP, 0.2 mg per kg per min), dibutyryl cyclic 3',5'-guanosine monophosphate (cyclic GMP, 0.05 mg per kg per min) or saline were infused over a period of 60 min. To prove the viability of the pouch and to show its ability to release gastrin with proper stimulation, bethanechol chloride (urecholine) was infused into the gastric artery at the end of the experiment. Blood samples were taken from the portal vein and assayed for gastrin. Neither cyclic AMP nor cyclic GMP infusion was found to increase portal gastrin concentration to a significant degree. A marked increase in portal gastrin concentration however, was observed when bethanechol chloride was infused. These studies lend no support to the thesis that cyclic nucleotides mediate gastrin release in the dog.