Niilo Havu

Atrophic Gastritis and Helicobacter pylori Infection in Patients with Reflux Esophagitis Treated with Omeprazole or Fundoplication

BACKGROUND Helicobacter pylori infection plays an important part in the development of atrophic gastritis and intestinal metaplasia, conditions that predispose patients gastric cancer. Profound suppression of gastric acid is associated with increased severity of gastritis caused by H. pylori, but it is not known whether acid suppression increases the risk of atrophic gastritis. METHODS We studied patients from two separate cohorts who were being treated for reflux esophagitis: 72 patients treated with fundoplication in Sweden and 105 treated with omeprazole (20 to 40 mg once daily) in the Netherlands. In both cohorts, the patients were followed for an average of five years (range, three to eight). After fundoplication, the patients did not receive acid-suppressive therapy. The presence of H. pylori was assessed at the first visit by histologic evaluation in the fundoplication group and by histologic and serologic evaluation in the omeprazole group. The patients were not treated for H. pylori infection. Before treatment and during follow-up, the patients underwent repeated gastroscopy, with biopsy sampling for histologic evaluation. RESULTS Among the patients treated with fundoplication, atrophic gastritis did not develop in any of the 31 who were infected with H. pylori at base line or the 41 who were not infected; 1 patient infected with H. pylori had atrophic gastritis before treatment that persisted after treatment. Among the patients treated with omeprazole, none of whom had atrophic gastritis at base line, atrophic gastritis developed in 18 of the 59 infected with H. pylori(P<0.001) and 2 of the 46 who were not infected (P=0.62). CONCLUSIONS Patients with reflux esophagitis and H. pylori infection who are treated with omeprazole are at increased risk of atrophic gastritis.

Toxicological studies on omeprazole

As part of the safety evaluation of the gastric antisecretory drug, omeprazole, toxicological studies have been performed in several species of animals. The acute toxicity after oral administration to rodents was low. The oral LD50 value was above 4 g/kg. The general toxicity after repeated administration has been studied in rats and dogs. No clinical signs of adverse reactions were seen. Some minor changes in hematology parameters were observed. In rats and mice decreases in the erythrocyte count, hematocrit and hemoglobin have occasionally been found at doses of 125 mumol/kg/day and more. Hyperplasia of oxyntic mucosal cells, concomitant with increases in stomach weight, oxyntic mucosal thickness and folding, has been observed in the species investigated, the dog, rat and mouse. In addition, slight chief cell atrophy and eosinophilia of the chief cell granules were observed in rats. The oxyntic mucosal effects were reversible upon treatment being discontinued. In the oncogenicity studies, gastric carcinoids occurred in the rat but not in the mouse. Investigations of the carcinoids showed that the vast majority of the endocrine cells could be characterised as ECL-cells. The hyperplasia of oxyntic mucosal cells, including hyperplasia of endocrine ECL-cells and development of gastric carcinoids in rats, is attributable to the pronounced hypergastrinemia produced as a secondary effect of almost complete inhibition of acid secretion by the large doses of omeprazole used in the toxicity studies. In agreement with this hypothesis, the hyperplasia of the oxyntic cells was prevented by antrectomy. The reproduction studies performed in rats and rabbits showed no sign of fetal toxicity or teratogenic effect. The results of the short-term mutagenicity tests, Ames test, the micronucleus test in mice and the mouse lymphoma test were all negative.

Histopathological Classification of Nonantral Gastric Endocrine Growths in Man

Recently, the gastric endocrine system has been recognized as the origin of benign and malignant tumors in pernicious anemia. It has also been found that the gastric endocrine cells respond to permanent elevation of serum gastrin levels induced by changes in acid secretion in response to surgical procedures, drug therapy and age. Therefore, a definition of nonantral gastric endocrine hyperplasia (simple or diffuse, linear or chain-forming, micronodular, adenomatoid), dysplasia (enlarging or fusing micronodules, microinvasion, nodular growth) and neoplasia (intramucosal carcinoid, invasive carcinoid) is presented. The individual entities are illustrated, together with the literature discussed and the techniques for their identification presented.

Enterochromaffin-Like Cell Carcinoids of Gastric Mucosa in Rats after Life-Long Inhibition of Gastric Secretion

Small intramucosal tumours in the oxyntic area of the rat stomach were observed in an oncogenicity study with omeprazole. The tumours could be defined as carcinoids of enterochromaffin-like (ECL) cell origin. ECL cells occur exclusively in oxyntic mucosa and respond to the trophic hormone gastrin with a proliferation that becomes exaggerated in old rats. Inhibition of gastric acid secretion is known to induce hypergastrinaemia in rats. According to the common concept of endocrine cells, a sustained hormonal stimulation with gastrin may induce a continuous gradient between hyperplasia and neoplasia of the ECL cells. The tumours found are thus to be regarded as hormone-induced endocrine tumours of the ECL cells in the stomach. The ECL-cell tumours of the rats in the oncogenicity study appeared to belong to the low-malignancy type of carcinoids and did not make their appearance until the end-life period of the study. The sex and species differences observed may be explained by inherent differences in gastrin response, spontaneous ECL cell density or in responsiveness to gastrin-stimulated ECL cell proliferation between sexes and species.

Enterochromaffin-Like Cell Carcinoids in the Rat Gastric Mucosa following Long-Term Administration of Ranitidine

Long-term administration of some long-acting inhibitors of gastric acid secretion has been associated with the development of gastric enterochromaffin-like (ECL)-cell carcinoids in the rat. It has been argued that short-acting, surmountable histamine H2-receptor blockers such as ranitidine do not cause carcinoids. In this study, female rats (n = 100) were treated for 2 years with the histamine H2-receptor blocker ranitidine, 2 g/kg/day in the diet. Specimens from the stomachs of all rats, including 50 controls, were stained for argyrophil cells. Plasma gastrin and ranitidine levels were measured in separate groups of rats at different times during the study. The mean plasma level of ranitidine was 37.5 mumol/l, measured at midnight when the maximal level after food intake was expected. The resulting acid inhibition was associated with an approximately 3-fold increase in plasma gastrin which persisted throughout the whole period of the study. The ranitidine treatment resulted in a pronounced hyperplasia of gastric ECL cells. In 19 rats carcinoids were found, 4 of which were micro-invasive. No carcinoids were found in the control animals. The results provide further support for the gastrin mechanism, i.e. that the development of ECL-cell carcinoids in the rat gastric mucosa is a consequence of prolonged hypergastrinaemia and is not a unique effect of any individual acid-inhibiting drug.

Partial gastric corpectomy results in hypergastrinemia and development of gastric enterochromaffinlike-cell carcinoids in the rat

Studies in the rat have shown that partial gastric corpectomy, in which about 75% of the acid-producing oxyntic mucosa was removed, leads to markedly reduced acid secretion and a feedback increase in the plasma gastrin levels. Ten weeks after operation, the gastric enterochromaffin (ECL)-like cell density in the remaining part of the oxyntic mucosa had increased significantly. In the present study, the effects on the gastric ECL cells of lifelong persistent hypergastrinemia induced by partial (75%) corpectomy have been investigated. Seventy-five partially corpectomized rats and 40 control rats were investigated for plasma gastrin and oxyntic mucosal changes in a 124-week study. The partially corpectomized rats showed increased plasma gastrin levels after the operation; the mean increase compared with the controls was almost 10-fold during the entire study. The remaining oxyntic mucosa of the partially corpectomized rats differed from that of control rats in two respects, showing first general hypertrophy and second a marked hyperplasia of argyrophil ECL cells. The degree and incidence of these changes increased towards the end of the study, i.e., in the aging rats. An age-related increase in ECL-cell density occurred spontaneously also in the control rats but to a lesser extent than in the partially corpectomized group. ECL-cell carcinoids were found in the oxyntic mucosa of 26 of the 75 partially corpectomized rats. The first carcinoid was found 78 weeks after the beginning of the study. Six rats with carcinoids (23%) were found before week 104 (2 years) and the remainder, 20 (77%), were discovered later. No carcinoid tumor was found in the control rats. It is concluded that lifelong hypergastrinemia induced by partial corpectomy leads to the development of ECL-cell carcinoids in the oxyntic mucosa of some rats towards the end of their life span. This observation strongly supports the hypothesis that the gastric ECL-cell carcinoids found in rats treated with antisecretory drugs are caused by long-standing hypergastrinemia developing secondary to inhibition of gastric acid secretion.

Qualitative Studies of Gastric Endocrine Cells in Patients Treated Long-term with Omeprazole

A total of 543 endoscopic biopsies (a mean of three tissue samples each) were taken from the gastric oxyntic mucosa of 122 patients suffering from reflux oesophagitis or peptic ulcer resistant to H2-receptor antagonist therapy. All were treated with omeprazole, 40 mg/day, until healing and then assigned to 20 mg/day for a mean of 13 months. Proliferative changes of endocrine cells were evaluated according to an internationally agreed classification and the paraffin sections were stained with haematoxylin-eosin and Sevier-Munger silver. Only hyperplastic (no dysplastic or neoplastic) lesions of endocrine cells were observed in 11-19% of patients examined, the incidence and severity of these lesions being unaffected by treatment. A relationship between linear and/or micronodular hyperplasia and chronic gastritis was observed.

Gastric Endocrine Cells and Gastritis in Patients Receiving Long-Term Omeprazole Treatment

Both argyrophil endocrine cells and gastritis were investigated in 2,120 biopsies of gastric corpus mucosa from 443 out of 448 patients receiving long-term (for periods ranging from several months to 4 years) omeprazole treatment. None of the patients showed neoplasia or dysplasia, either endocrine or non-endocrine. In 123 out of 443 patients (27.8%), endocrine hyperplasia of diffuse (9.3%), linear (4.1%) or micronodular (14.4%) type was detected either before or at some time during treatment. Chronic atrophic gastritis was found in 45 (10.2%) patients, 60% of whom also showed micronodular hyperplasia. In patients with chronic atrophic gastritis, micronodular hyperplasia occurred in 49% of 96 biopsies, compared with 6% of 1,083 biopsies from patients with non-atrophic chronic gastritis and 2% of 941 biopsies from patients with no evidence of gastritis. In 202 patients treated with omeprazole for at least 330 days, the incidence of micronodular hyperplasia increased from 2.5% at the first biopsy to 10.4% at the final biopsy, while the incidence of chronic atrophic gastritis increased from 1.0% to 13.0%. The present and parallel studies suggest that progression of gastritis is inherent in the natural history of acid-related diseases, while endocrine cell changes are mostly secondary to gastritis-related gland atrophy and have no tumorigenic potential.

Argyrophil Cell Hyperplasia Associated with Chronic Corpus Gastritis in Gastric Ulcer Disease

Argyrophil cell (AC) hyperplasia in corpus mucosa was investigated in 53 patients with chronic gastric ulcer disease not previously treated with antisecretory drugs. Mucosal biopsies were taken stepwise from the posterior wall in the corpus area of the stomach. Of 117 biopsy sites, 28 showed gastritis without atrophy, 85 showed chronic atrophic gastritis of varying degrees while 4 biopsies showed a normal mucosa. About one third (38%) showed a normal AC pattern. Of the remaining two thirds (62%), 45% had simple AC hyperplasia, 18% had linear and 37% had micronodular AC hyperplasia. A strong association was found between focal (linear/micronodular) AC hyperplasia and chronic atrophic gastritis. It is concluded that focal AC hyperplasia is a common phenomenon in gastric ulcer patients and is inherently related to the spontaneous development of atrophy in the corpus mucosa of these patients.

Effect of 7 Years’ Daily Oral Administration of Omeprazole to Beagle Dogs

Ten beagle dogs were given omeprazole orally at a dose of 0.17 mg/kg (0.5 mumol/kg) daily for 7 years. Six dogs served as controls. Regularly evaluated criteria were clinical signs, body weight, food consumption, rectal temperature, electrocardiography, hematology, blood chemistry, urinalysis, ophthalmoscopy, gastroscopic examination including gastric mucosal biopsy sampling for histological evaluation, pharmacokinetics of omeprazole, and plasma gastrin levels. After approximately 5 years, a quantitative gastric acid secretion test was performed. No treatment-related adverse clinical signs or effects were observed in the dogs, and all animals survived to term. The annual gastroscopy with histological examinations of gastric mucosa did not show any treatment-related changes. At all investigations and in all dogs, the parietal cells were morphologically normal, and there were no changes of pattern or any increase in the number of argyrophil enterochromaffin-like cells compared to the control animals. In the plasma samples collected 24 h after dosing, there were no significant differences in either basal or meal-stimulated gastrin levels between the controls and the omeprazole-treated animals. Peak plasma concentration of omeprazole occurred within 2 h of dosing. The area under the concentration curve (AUC) was not affected by dosing over 7 years and was in good agreement with the AUC in humans given a dose of 20 mg omeprazole daily. Acid secretion tests after 5 years of treatment showed that the mean inhibition of acid secretion by omeprazole 4-7 h after dosing was as expected--about 50%.(ABSTRACT TRUNCATED AT 250 WORDS)