Importance of gastric acid in gastric ulcer formation in rabbits with antibody-induced prostaglandin deficiency

Cyclooxygenase knockout mice: models for elucidating isoform-specific functions

The development of cyclooxygenase (COX) deficient mice has allowed investigation into the individual physiological roles of the COX-1 and COX-2 isoforms. In the following article, the phenotypes of the two Ptgs (genes coding for COX-1 and COX-2) knockouts are summarized, and recent studies to investigate the effects of COX deficiency on cancer susceptibility, inflammatory response, gastric ulceration, and female reproductive processes are discussed. Also, the development and potential uses of mice deficient in both COX isoforms and mice containing only a single copy of one isoform are discussed. Additionally, when the data permit, the effects of genetic ablation of COX activity are compared with those of pharmacological inhibition of COX activity by nonsteroidal anti-inflammatory drugs. The data suggest that prostaglandins derived via the individual COX isoforms have separate as well as common functions. However, for the maintenance of normal physiology, it appears that deficiency of COX-2 has more profound effects than deficiency of COX-1.

Eicosanoids and the gastrointestinal tract

Determining the role of eicosanoids in gastrointestinal physiology and pathophysiology has been an active area of investigation over the past 20 years. The landmark discovery of prostaglandin endoperoxide synthase and other enzymes involved in the production of arachidonic acid products (lipoxygenases and epoxygenases) ushered in a new era of research. The goal of this review is to distill a large body of work pertaining to studies of eicosanoids in the gastrointestinal tract. This review has been organized according both to functional (secretion and motility) and disease-related (inflammation, mucosal injury, and neoplasia) effects. The aim of this article is to present a clear summary of this area of gastroenterology so that future research can be directed in a logical and productive manner.

Laboratory medicine in ulcer disease

The role of laboratory medicine in ulcer disease is poorly defined. However there is increasing evidence of the clinical usefulness of some laboratory tests that investigate secretory functions and defensive properties of the stomach, gastrointestinal hormones and Helicobacter pylori infection. These tests may modify the clinical management of patients with peptic ulcer by identifying H. pylori positive subjects, patients with high acid output, patients who do not respond to antisecretory therapy, and patients with high gastrin levels in whom Zollinger-Ellison syndrome may be suspected. Here we review the clinical value of laboratory tests in ulcer disease, particularly as concerns the cost/benefit ratio. The relative merits of these tests are described giving an indication of their possible role in the diagnostic algorithm.

Omeprazole ameliorates aspirin-induced gastroduodenal injury

Aspirin and nonsteroidal antiinflammatory drugs (NSAIDs) damage the gastroduodenal epithelium by two mechanisms: direct toxic effects and effects related to the depletion of endogenous prostaglandins. The prostaglandin-depleted mucosa has increased susceptibility to luminal aggressive factors, yet the role of acid in the pathogenesis of the NSAID ulcer is controversial. In humans, standard doses of H2-receptor antagonists prevent only duodenal injury and provide no protection for the gastric mucosa. It is not known whether more potent suppression of acid can prevent NSAID damage. Twenty healthy volunteers were randomized to a double-blind, placebo-controlled, crossover study to determine if omeprazole, 40 mg/day prevents gastroduodenal injury due to two weeks of aspirin administration (650 mg four times a day). The severity of mucosal injury was quantitated by endoscopy and stratified by a scale from 0 (normal) to 4 (ulcer). Fourteen of the 20 subjects had less gastric injury during cotherapy with omeprazole. All six with no difference received aspirin plus omeprazole in the first treatment period. Omeprazole significantly decreased aspirin-induced gastric mucosal injury (P < 0.001, Wilcoxon signed-rank test). Omeprazole protected 85% of subjects from extensive gastric erosions (often associated with evidence of intraluminal bleeding) or ulceration, whereas 70% of the subjects developed aspirin-induced grades 3 and 4 gastric injury on placebo (P < 0.01 by chi 2). No subject taking omeprazole developed duodenal injury of any grade, while 50% taking placebo developed erosions and 15% had ulcer (P < 0.001). Medication side effects were mild in the majority of subjects.(ABSTRACT TRUNCATED AT 250 WORDS)