Pepsinogen release and acid secretion from human and guinea pig gastric mucosa compromised by hypoxia, endotoxin, or critical illness

Intragastric pH of foals admitted to the intensive care unit

Background

Intragastric pH profiles of neonatal foals admitted to the intensive care unit (ICU) remain poorly characterized.

Hypothesis/Objectives

To determine intragastric pH profiles and clinical parameters associated with intragastric pH in foals admitted to the ICU.

Animals

Forty‐two neonatal foals admitted to the ICU and requiring placement of an indwelling nasogastric tube for nutritional management were included.

Methods

Intragastric pH was measured for 24 hours from the time of admission. Mean pH, % time pH <4, and % time pH >4 were determined for each foal. History, clinical findings, and clinicopathological data recorded at the time of presentation were collected.

Results

The mean pH of included foals was 5.5 ± 1.8. The median % time pH <4 was 6.3% (range: 0‐99). A history of placentitis was associated with greater mean pH (median 5.3 (range: 0.9‐7.8) versus median 7.2 (5.9‐11.3); P = .002) and less % time pH <4 (median 13 (0‐99.6) versus median 0.1 (0‐7.2); P = .01). Foals with diarrhea had a greater % time pH <4 (median 4.6% (0‐99) versus median 28.8% (1.4‐57.48); P = .02). Foals with a pH >4 for >50% recording time had a lower PaO₂ (mean difference 25.0 mm Hg; 95% confidence interval [CI], 14.4‐35.6; P = .03) and higher PaCO₂ (mean difference 14.9 mm Hg; 95% CI, 4.7‐25.2; P = .02). Surviving foals had a lower mean median hourly pH (P = .02).

Conclusions and Clinical Importance

Intragastric pH profiles were unpredictable and mostly >4 for >80% of the recording time. This study does not support the indiscriminate administration of acid suppressive treatment.

The pepsinogen releasing effect of Helicobacter pylori lipopolysaccharide

BACKGROUND

Helicobacter pylori lipopolysaccharide (LPS) affects pepsinogen release by a nontoxic mechanism. We hypothesized that this effect was characteristic of the organism and related to the clinical status of the strain.

MATERIALS AND METHODS

LPS was isolated from 11 H. pylori strains whose pathogenic profile was known and four other nongastric bacteria. The effects of luminal LPS on guinea pig gastric mucosal pepsinogen release was evaluated using the Ussing chamber technique. CCK-8 (10(-9)M) was used as a positive control.

RESULTS

H. pylori LPS dose-dependently stimulated pepsinogen release with a maximal stimulation at 250 microg/ml (approximately 4500; p < .001 vs. control). LPS from other Helicobacter or Campylobacter species had no effect on pepsinogen release. ANOVA demonstrated significant differences in the efficacies of pepsinogen release between the 11 clinical H. pylori strains (p < .0001) despite the fact that they were all cagA+ and 90 had the cytotoxic vacA subtype s1. Physical and chemical disruption of the LPS suggested that both the structure and the carbohydrate composition of this molecule may play a critical role in pepsinogen release. Polymyxin B partly (p < .03) inhibited and dephosphorylation completely inhibited (p = .0002) LPS-stimulated pepsinogen release.

CONCLUSION

Pepsinogen release is an innate property of all cagA+H. pylori LPS. The structure of the molecule and composition of side-chains are important in this response which appears to be partially lipid A driven.

Helicobacter pylori lipopolysaccharide stimulates gastric mucosal pepsinogen secretion

The effect of Helicobacter pylori lipopolysaccharide on guinea pig gastric mucosal pepsinogen secretion has been examined using an Ussing chamber technique. Luminal addition of H. pylori lipopolysaccharide resulted in a fifty-fold stimulation of pepsinogen secretion compared to a twelve-fold increase with E. coli lipopolysaccharide. Electron microscopy showed marked degranulation of zymogen granules but no evidence of chief cell disruption.