Basal and pentagastrin-stimulated gastric acid secretory rates in normal children and in those with peptic ulcer disease

Consideration of the Development of the Gastrointestinal Tract in the Choice of Species for Regulatory Juvenile Studies

Although the rat is close to being the automatic choice for regulatory juvenile toxicity studies, there are several shortcomings in this model. Choosing a species should take into serious consideration the importance of gastrointestinal tract development in the period before weaning as this may have a major effect on exposure. A comparison of the anatomical changes in the stomach and small intestine of mini-pig and rat show that the mini-pig is a far closer model for man than is the rat, although there are a few unusual aspects of small intestinal development in the mini-pig. Considerations of the development of the gastrointestinal tract and choice of species have the potential to affect safety assessment and should be a prime consideration when planning an investigation. Birth Defects Research 110:56-62, 2018. © 2017 Wiley Periodicals, Inc.

Influence of Helicobacter pylori infection on gastric acid secretion in pre-school Bangladeshi children

BACKGROUND

The effect of Helicobacter pylori (H. pylori) infection on gastric acid secretion (GAS) is poorly defined in children.

OBJECTIVE

To determine whether H. pylori infection is associated with abnormal GAS in children.

METHODS

We studied 30 H. pylori-infected children (identified by a positive urea breath test) and 30 noninfected children of both sexes, aged 2-5 years. Gastric pH and GAS were measured before and 8 weeks after the completion of a 2-week course of anti- H. pylori therapy (omeprazole, clarithromycin, and amoxicillin). Gastric acid output (GAO) was quantified during a 1-h basal period (GAO-B) (mmol/h) and a 1-hour stimulated period (GAO-S) (mmol/hour) following subcutaneous administration of pentagastrin (6 μg/kg).

RESULTS

A significantly greater number of infected children had a high gastric pH (>4.0, p = 0.03) compared with the noninfected group. GAO-B and GAO-S in H. pylori-infected children were significantly lower, around 50%, compared with children without H. pylori infection. H. pylori-eradication therapy resulted in a rise of both the mean GAO-B (paired t-test before vs. after therapy; 0.28 ± 0.40 vs. 0.62 ± 1.0, p = 0.12) and GAO-S (before vs. after therapy; 2.0 ± 1.4 vs. 3.4 ± 2.5, p = 0.001), with values reaching equivalence to those in the H. pylori-negative children (0.71 ± 0.56 for BAO, 3.3 ± 2.0 for SAO, p = NS).

CONCLUSION

The results suggest that the gastric barrier is compromised in children with H. pylori infection in Bangladesh. Improvement of GAO following anti- H. pylori therapy suggests a causal link between H. pylori infection and depressed GAO in this population.

Quality evaluation of extemporaneous delayed-release liquid formulations of lansoprazole

PURPOSE

The quality attributes of extemporaneous delayed-release liquid formulations of lansoprazole for oral administration were evaluated.

METHODS

A novel liquid formulation (3 mg/mL) of Prevacid FasTab in an Ora-Blend vehicle was prepared and compared with the Prevacid FasTab 30 mg and Prevacid-sodium bicarbonate 1 M formulation (3 mg/mL). The latter formulation was combined with hydrochloric acid 0.1 N, and the remaining lansoprazole content was assayed by high-performance liquid chromatography (HPLC). A batch of delayed-release liquid formulation was prepared to evaluate content uniformity. For content assay, three samples were prepared for each evaluated condition and each sample was analyzed in triplicate by HPLC.

RESULTS

The lansoprazole in the sodium bicarbonate formulation was extensively degraded by quantities of hydrochloric acid 0.1 N in excess of 100 mL. Storage time and temperature had a significant effect on lansoprazole stability in the Ora-Blend formulation. The drug remained stable for seven days when the formulation was stored at 4.5-5.5 °C, but storage at 21-22 °C or the reduction of pH with citric acid accelerated lansoprazole degradation. The amount of lansoprazole released from the Ora-Blend formulation during the buffer stage of the dissolution test decreased with increases in formulation storage time, in formulation storage temperature, and in the amount of lansoprazole released and degraded during the acid stage of the test.

CONCLUSION

An extemporaneous formulation consisting of lansoprazole microgranules in Ora-Blend maintained acceptable quality attributes when stored for three days at 4.5-5.5 °C.

Helicobacter pylori infection, iron absorption, and gastric acid secretion in Bangladeshi children

BACKGROUND

Nonheme-iron absorption requires an acidic milieu. Reduced gastric acid output as a consequence of Helicobacter pylori infection could be an important limiting factor for iron absorption.

OBJECTIVE

We measured gastric acid output and iron absorption from a non-water-soluble iron compound (ferrous fumarate) and a water-soluble iron compound (ferrous sulfate) in children with and without H. pylori infection.

DESIGN

Gastric acid output was quantified before (basal acid output, or BAO) and after pentagastrin stimulation (stimulated acid output, or SAO) in 2-5-y-old children with iron deficiency anemia who were (n = 13) or were not (n = 12) infected with H. pylori. Iron absorption was measured by using a double-stable-isotope technique. H. pylori-infected children were studied before and after eradication therapy.

RESULTS

BAO and SAO were significantly lower in the H. pylori-infected children (0.2 +/- 0.2 and 1.6 +/- 0.9 mmol/h, respectively) than in the uninfected children (0.9 +/- 0.7 and 3.1 +/- 0.9 mmol/h, respectively; P = 0.01 and P < 0.005). BAO and SAO improved to 0.8 +/- 1.3 and 3.3 +/- 2.4 mmol/h, respectively, after therapy. Iron absorption from ferrous sulfate was significantly greater than that from ferrous fumarate both before (geometric : 19.7% compared with 5.3%; P < 0.0001) and after (22.5% compared with 6.4%; P < 0.0001) treatment in H. pylori-infected children. Corresponding values for uninfected children were 15.6% and 5.4%, respectively (P < 0.001; n = 12).

CONCLUSIONS

Iron absorption from ferrous fumarate was significantly lower than that from ferrous sulfate in both H. pylori-infected and uninfected Bangladeshi children. Treatment of H. pylori infection improved gastric acid output but did not significantly influence iron absorption. The efficacy of ferrous fumarate in iron fortification programs to prevent iron deficiency in young children should be evaluated.

Effect of Helicobacter pylori infection on gastric acid secretion and meal-stimulated serum gastrin in children

BACKGROUND

Comparative studies of gastric acid secretion in children related to Helicobacter pylori infection are lacking. The purpose of this study was to compare acid secretion and meal-stimulated gastrin in relation to H. pylori infection among pediatric patients.

MATERIALS AND METHODS

Thirty-six children aged 10-17 years (17 with H. pylori infection) undergoing diagnostic endoscopy participated in the study. Diagnoses included gastritis only (n = 23), duodenal ulcer (n = 5) and normal histology (n = 8). Gastric acid output was studied using the endoscopic gastric secretion test before and 2-3 months after H. pylori eradication. Meal-stimulated serum gastrin response was assessed before and 12 months after eradication.

RESULTS

H. pylori gastritis was typically antrum-predominant. Acid secretion was greater in H. pylori-positive patients with duodenal ulcer than in gastritis-only patients or controls [mean +/- standard error (SE): 6.56 +/- 1.4, 3.11 +/- 0.4 and 2.65 +/- 0.2 mEq/10 minutes, respectively; p <.001]. Stimulated acid secretion was higher in H. pylori-positive boys than girls (5.0 +/- 0.8 vs. 2.51 +/- 0.4 mEq/10 minutes, respectively; p <.05). Stimulated acid secretion pre- and post-H. pylori eradication was similar (5.47 +/- 0.8 vs. 4.67 +/- 0.9 mEq/10 minutes, respectively; p =.21). Increased basal and meal-stimulated gastrin release reversed following H. pylori eradication (e.g. basal from 134 to 46 pg/ml, p <.001 and peak from 544 to 133 pg/ml, p <.05).

CONCLUSIONS

H. pylori infection in children is associated with a marked but reversible increase in meal-stimulated serum gastrin release. Gastric acid hypersecretion in duodenal ulcer remains after H. pylori eradication, suggesting that the host factor plays a critical role in outcome of the infection.

The evaluation and treatment of gastrointestinal disease in children with cystinosis receiving cysteamine

OBJECTIVES

Cysteamine prevents organ damage in children with cystinosis, but may cause gastrointestinal (GI) symptoms. In this study we evaluated the nature of GI disease, and the value of omeprazole in controlling GI symptoms in these children.

STUDY DESIGN

Upper GI disease was evaluated with endoscopy, gastrin levels, and acid secretion studies after oral administration of cysteamine, before and after 16 weeks of therapy with omeprazole. A symptom score was devised.

RESULTS

Eleven children (mean age, 5.7 years) were studied. After cysteamine ingestion, before and after omeprazole therapy, the mean maximum acid output was significantly higher than the mean basal acid output. The maximum acid output was measured within 60 minutes of cysteamine ingestion and was reduced by omeprazole therapy (P<.01). The mean peak gastrin level was 30 minutes postcysteamine and was higher than baseline (P<.01). The initial mean symptom score (maximum score, 14) was 6.9 and fell to 0.7 (P<.0001) after 16 weeks of omeprazole therapy. At endoscopy, two children had diffuse gastric nodularity, and nearly all had cystine crystal deposits.

CONCLUSIONS

GI symptoms in children with cystinosis receiving cysteamine are often acid-mediated and improve with omeprazole. Cystine crystals were detected in the GI tract and may signify inadequate treatment with cysteamine.

Acid secretion and response to pentagastrin or omeprazole in human fetal stomach xenografts

BACKGROUND

The dual capacity of stomach tissue to secrete acid and to respond to secretagogues is indicative of the terminal stages of gastric functional maturation. In this study 6- to 10-week-old human fetal stomachs xenografted into nude mice were used to study parietal cells' functional maturation.

METHODS

Thirty-four transplants were microsurgically grafted either inside a pouch created on the nude peritoneum (n = 15) or on the host stomach and esophagus (n = 19). The mucosa of transplanted tissues was analyzed by immunohistochemical techniques to detect gastric cells. Gastric cell secretions were collected before and after pentagastrin or omeprazole treatment.

RESULTS

Parietal, G, and D cells were detected immunohistochemically only after 1 month of grafting. All xenografts actively secreted acid after 1 or 2 months' transplantation at each graft site. Acid secretion was significantly stimulated by intraperitoneally injected pentagastrin (mean pH +/- SD, 3.2 +/- 0.7 vs. 2.0 +/- 0.5; n = 10, P = 0.005) and was dramatically inhibited by intragastrically administered omeprazole (2.3 +/- 0.6 vs. 6.5 +/- 0.7; n = 15, P = 0.0007) after 5 hours.

CONCLUSION

Stomach xenografts were able to develop normally. Parietal cells were physiologically mature with functional proton pumps and active gastrin receptors, as demonstrated after omeprazole and pentagastrin treatment, respectively. Because stomach xenografts matured very rapidly, it is possible that a stomach xenograft model can be used for further studies on the functional maturation of human gastric epithelial cells, as well as the factors that influence this maturation in humans.

Peptic ulcer disease in children

A peptic ulcer in a child looks the same as it does in an adult, and many of the aetiologies of peptic ulcer disease in children are similar to those in adults. However, there are many differences between children and adults, especially in the areas of clinical presentation, the prevalences of different types of ulcer disease, and the prevalence of complications of ulcer disease. Therefore the approach to diagnosis and management in children is often at variance with that in adults. One important example is the approach to suspected Helicobacter pylori (H. pylori) disease in children, in which consensus groups have advised a considerably different approach in children. While the chapter deals with the full range of peptic ulcer disease in children, the focus is on those aspects in which there are differences between adults and children.

Lysosomal inclusions in gastric parietal cells in mucolipidosis type IV: a novel cause of achlorhydria and hypergastrinemia

Mucolipidosis type IV (ML-IV) is an autosomal recessive lysosomal storage disease that causes severe neurologic abnormalities. The brain disease is characterized by pigmented cytoplasmic granules in neurons and accumulation of lamellated membrane structures in lysosomes. The gastrointestinal disease in ML-IV was not previously recognized. Clinical examination of 20 patients with ML-IV (age range, 2-23 years) at the National Institutes of Health showed hypergastrinemia and constitutive achlorhydria. Endoscopic biopsy specimens from the gastric fundus, body, and antrum and from the duodenum of four such patients (ages 4, 6, 7, and 22 years) were evaluated histologically and by electron microscopy. Histologically, all gastric fundus and body biopsy specimens showed parietal cells in normal numbers. However, a striking cytoplasmic vacuolization of parietal cells was seen on hematoxylin and eosin stain. Electron microscopy showed the parietal cells to be markedly distended by large lysosomes containing lamellar, concentric, and cystic membranous inclusions. Additionally, chronic atrophic gastritis and enterochromaffin-like (ECL) cell hyperplasia were observed. Foveolar and chief cells in stomach and duodenum biopsy specimens were normal. We conclude that the cytoplasmic lysosomal inclusions in gastric parietal cells is a unique histologic feature of gastric biopsy in ML-IV.

Constitutive achlorhydria in mucolipidosis type IV

Mucolipidosis type IV is an autosomal recessive lysosomal storage disease of unknown etiology that causes severe neurological and ophthalmological abnormalities. In an attempt to obtain insight into the nature of the metabolic abnormality in this disorder, we prospectively evaluated 15 consecutive patients, aged 2 to 23 years, over a period of 22 months. The finding of iron deficiency in some of the patients led us to the discovery that all patients but one had markedly elevated blood gastrin levels. None had vitamin B12 deficiency. Gastroscopy in three patients showed normal gross appearance of the mucosa in two patients, 4 and 7 years old, and mucosal atrophy in a 22-year-old. Parietal cells were present in normal numbers and contained large cytoplasmic inclusions that were confirmed immunohistochemically to be lysosomal in nature. Other gastric epithelial cells appeared normal. Parietal cells contained very few tubulovesicular membranes, suggesting cellular activation, whereas apical canaliculi appeared relatively nonactivated. Both subunits of the parietal cell H+/K+-ATPase were present, and both partially colocalized with f-actin at the apical membrane. We conclude that patients with mucolipidosis type IV are constitutively achlorhydric and have partially activated parietal cells. We hypothesize that the defective protein in this disease is closely associated with the final stages of parietal cell activation and is critical for a specific type of cellular vacuolar trafficking between the cytoplasm and the apical membrane domain.

Diurnal variation in intragastric pH in children with and without peptic ulcers

Diurnal variation in intragastric pH in children with peptic ulcers has not been previously reported. Therefore, we monitored intragastric pH during a 24-h period in 82 subjects (10 children with gastric ulcers, 9 children with duodenal ulcers, 58 non-ulcer (comparison group) children, and 5 healthy adults) using a monopolar glass pH electrode. The percent of readings below pH 2, 3, 4, and 5 for each subject was calculated and compared between the comparison group and the two ulcer groups using means and slopes (i.e. changes in percent with age for each group) of percent readings for each pH analysis. In the comparison group children, gastric acidity increased with age and reached adult levels by 14 y. Mean readings for all pH analyses in gastric ulcer children were lower than those in age-adjusted comparison children (p < 0.05). The slopes of the relationships between age and the percent time below any pH for the gastric ulcer group were different from those in the comparison group (p < 0.05) and were negative for all pH analyses. The mean time below pH 2 in children with duodenal ulcers was greater than that in age-adjusted comparison children (p = 0.002). The slope of the relationship between age and the percent time below pH 2 in the duodenal ulcer group was different from that in the comparison group (p < 0.05). Gastric acidity in children with primary gastric ulcers was reduced during childhood, but in children with primary duodenal ulcer, gastric acidity was at or above adult levels.

Metabolic complications of the use of stomach for urinary reconstruction

A total of 34 children with normal renal function underwent either gastrocystoplasty or continent urinary reservoirs with stomach at our institutions. Severe hypochloremic hypokalemic metabolic alkalosis developed in 2 patients, manifested by intractable seizure disorder in 1 and altered mental status with respiratory depression in 1. Symptoms developed at 4 and 6 months, respectively. Despite severe alkalosis, urinary pH was less than 5.0 and fractional excretion of chloride remained high in both patients. Resuscitation with sodium chloride, arginine hydrochloride and potassium chloride restored electrolyte balance in less than 48 hours in both patients. Serum gastrin was slightly elevated in 1 patient (137 pg./ml., normal 0 to 125) who responded to long-term histamine-blocker therapy. The other patient had significant hypergastrinemia (624 pg./ml.) with secondary hyperaldosteronism. Maximum doses of histamine blockers, oral replacement of sodium chloride and potassium chloride, and the proton pump inhibitor omeprazole failed to control recurrent bouts of severe hypochloremic metabolic alkalosis. This patient ultimately underwent removal of three-quarters of the gastric augmentation and replacement with ileum. Postoperatively, serum gastrin levels and electrolytes reverted to normal. The pathophysiology of this potentially lethal complication is further discussed.

Menetrier's disease associated with formula protein allergy and small intestinal injury in an infant

Menetrier's disease in infancy is extremely rare, and its natural course has not been studied in detail. The present case report describes an infant whose initial diagnosis was formula protein allergy and who developed gastric outlet obstruction by 3 months of age. The diagnosis of Menetrier's disease was suggested by characteristic radiological, pathological, and functional abnormalities of the stomach. Small intestinal partial villous atrophy, malabsorption, and protein loss from both the stomach and the intestine were documented. Cytomegalovirus infection was excluded. There was no evidence for an immune deficiency. The described features and an unrelenting course suggest that infantile Menetrier's disease may be an entity distinct from the childhood and adult forms.

Efficacy of cimetidine for gastric acid suppression in pediatric patients

The efficacy of oral cimetidine for gastric acid suppression in pediatric patients was examined in a double-blind study. Twenty-seven patients with gastroesophageal reflux-related gastrointestinal symptoms, pulmonary symptoms, or both were given randomly determined doses of cimetidine. Response was evaluated by continuous intragastric monitoring with a pH probe. Twenty-three patients were given cimetidine doses of 5,7.5, and 10 mg/kg; eight of these patients were also given additional doses of 15 mg/kg. Four patients received only 10 and 15 mg/kg, because of previous poor clinical response to the lower dosages. The onset of gastric pH greater than 4 was delayed more than 2 hours in 50% of patients with responses to the 5 mg/kg dose. Of the patients with responses to the 10 mg/kg dose, 75% had showed a rise in gastric pH greater than 4 within 2 hours. With respect to the duration of gastric acid suppression, 70% of patients receiving 5 mg/kg doses and 52% of those receiving 7.5 mg/kg doses did not have a sustained a response for more than 2 hours, whereas 75% of patients receiving 10 mg/kg doses had gastric acid suppression for longer than 2 hours. Of the patients receiving 15 mg/kg doses, 75% had a response for more than 2 hours; 50% of these patients had a response for more than 3 hours. We conclude that recommended doses of cimetidine for children may not be optimal for adequate gastric acid suppression.

Antral gastrin cell hyperfunction in children. A functional and immunocytochemical report

Antral gastrin cell hyperfunction is a rare condition, often associated with severe duodenal ulcer disease. In children, clinical and functional characteristics of this syndrome are poorly known. Two cases are described here: one child had melena and the other had moderate abdominal pain, both without peptic ulceration. Basal and postprandial increase of gastrin levels showed a response over the upper normal range, indicating gastrin cell hyperfunction. Acid hypersecretion, both basal and after pentagastrin stimulation, was also found in the two children, confirming the biological effect of their sustained hypergastrinemia. Gastrin cell counts were within the normal range, while the number of somatostatin D cells was significantly reduced. This report stresses the importance of diagnosing antral gastrin cell hyperfunction in children because this unrecognized condition may manifest with serious complications (bleeding) or nonspecific abdominal symptoms.

Peptic ulcer disease in children

Primary duodenal ulcer disease occurs in children of all ages, but is most often seen in those over 10 years. As in the adult, it often pursues a chronic course. Primary gastric ulcer is seen in children under 6 years, is more unusual, and does not tend to recur. Stress ulcers are seen most often in infants and in critically ill children and are asymptomatic until the complications of hemorrhage or perforation appear. Drug-related ulcers are being seen more frequently as the use of nonsteroidal anti-inflammatory agents increases. With the use of new therapeutic agents, management has been simplified and surgical intervention has become a rarity. Helicobacter pylori is now a recognized cause of antral gastritis and ulceration in the child.

Suppression of gastric acid secretion by intravenous administration of famotidine in children

This study was designed to establish appropriate dosing requirements for intravenous use of famotidine, a new H2-receptor antagonist, in pediatric patients. Eighteen children, 2 to 69 months of age (mean +/- SD: 31 +/- 23 months), were treated with intravenously administered famotidine to prevent bleeding of the upper gastrointestinal tract. Continuous intragastric pH monitoring was carried out to ascertain the effectiveness of various intravenous doses. An initial dose of 0.4 mg/kg was given and repeated only after the intragastric pH had dropped to less than 4.0 for 2 hours. Increased doses were given (0.8, 1.2, and 1.6 mg/kg) if the previous dose did not raise the intragastric pH to greater than 4.0 for greater than or equal to 6 hours. Sixteen patients achieved an intragastric pH greater than or equal to 4.0 for greater than or equal to 6 hours, 13 with a dose of 0.4 mg/kg, and three with a dose of 0.8 mg/kg. The mean duration of continuous pH greater than 4.0 per dose was 9.0 +/- 7.5 hours. Ten patients received two or more intravenous doses of famotidine; the mean duration of pH greater than 4.0 after the second dose was less than that after the first (14.9 +/- 8.0 hours vs 6.9 +/- 3.2 hours, p less than 0.01). We conclude that intravenous famotidine therapy raises gastric pH to greater than 4.0 for approximately 9 hours in most children. Prolonged intravenous use of famotidine rapidly leads to a decreased duration of efficacy, necessitating intragastric pH monitoring to assess the effectiveness of treatment.

Pseudo-Zollinger--Ellison syndrome in a child presenting with anemia

Pseudo-Zollinger--Ellison syndrome appears to very rarely afflict young children. Hypergastrinemia, regardless of the etiology, presents with signs and symptoms of nonhealing or multiple gastric or duodenal ulcers, or both. We present a 7-yr-old boy with fasting hypergastrinemia (serum gastrin 200-500 pg/ml) who had mild to moderate iron deficiency anemia, but was asymptomatic. Stool guaiac was positive and gastric acid secretion was almost 40-fold above normal. Endoscopy showed multiple small gastric fundal ulcerations and severe gastritis. Workup for Zollinger--Ellison syndrome was negative. Changes in serum gastrin levels after secretin injection and after ingestion of a protein meal were compatible with those noted in adults with pseudo-Zollinger--Ellison syndrome. This child may be the first case of pseudo-Zollinger--Ellison syndrome under the age of 17 yr.

Absence of tachyphylaxis in gastric acid secretion during pentagastrin infusion

Tachyphylaxis to stimulation of gastric juice secretion during intravenous pentagastrin (PG) infusion has been reported in animal studies. We assessed the course of gastric response to PG 2 micrograms/kg/hr over eight hours in eight healthy subjects. Peak H+, pepsin, and volume secretions occurred during the second half hour of stimulation. Peak H+ output was 11.6 +/- 1.3 mmol/0.5 hr or 7.6 +/- 0.8% of the total eight-hour secretion. During subsequent half-hour collection intervals, there was no significant decline in response, and the average output was 10.3 +/- 0.4 mmol/0.5 hr (6.5 +/- 0.1%). Peak pepsin and volume secretions were respectively 10.0 +/- 1.4% (74.8 +/- 11.6 mg/0.5 hr) and 8.8 +/- 1.1% (146.3 +/- 17.4 mL/0.5 hr) of the total eight-hour secretion. Although there was a significant decline in pepsin and volume response subsequent to the peak output, the decline was not continuous, and pepsin and volume secretions were maintained, respectively, at 6.0 +/- 0.2% (46.1 +/- 2.5 mg/0.5 hr) and 6.2 +/- 0.1% (107.5 +/- 3.0 mL/0.5 hr) of the total eight-hour secretion. Our study did not demonstrate any tachyphylaxis in H+ response to continuous PG stimulation. This model appears to be a valid tool for the assessment of histamine-H2 antagonist effects on stimulated gastric juice secretion over 8 hours in humans.

Gastric acid secretory function in preterm infants

To establish normal values for gastric secretory function in preterm infants, we studied 34 healthy preterm infants once a week during hospitalization. Basal acid output, pentagastrin-stimulated acid output, fasting serum gastrin, and fasting serum pancreatic polypeptide were measured during each study. Basal acid output at 1 week of age was 12 mumol/kg/hr, increasing over the first 4 weeks to 30 mumol/kg/hr. Administration of pentagastrin 6 micrograms/kg subcutaneously increased acid output in all age groups. Pentagastrin-stimulated acid output at 1 week was 21 mumol/kg/hr, increasing over the first 4 weeks to 44 mumol/kg/hr. Acid secretion did not change significantly over the next 4 to 6 weeks. Fasting serum gastrin concentration was stable over the first 6 weeks of life, but doubled during the end of the second month. Pancreatic polypeptide was found at low levels throughout the study. These studies confirm that the majority of healthy preterm infants secrete acid in quantity sufficient to maintain the gastric pH less than or equal to 4, providing a barrier to bacteria and protein antigens.