Inhibition of gastrin-stimulated enterochromaffin-like cell proliferation and mucosal histamine production in the rat stomach by the somatostatin analogue octreotide

Type 1 and 2 gastric carcinoid tumors: long-term follow-up of the efficacy of treatment with a slow-release somatostatin analogue

Little is known about the long-term results of treating gastric carcinoid tumors with a slow-release somatostatin analogue. We report three patients with type 1 and 2 gastric carcinoid tumors who were treated in the above mentioned way and followed for 27-50 months. In all cases, alternative endoscopic or surgical management was considered but deemed inappropriate. Treatment with a slow-release somatostatin analogue was begun in light of a favorable recent report. The result was regression or complete disappearance of macroscopic fundal tumors. No side-effects were reported and, most notably, none of the patients developed gallstones. This small study may help define the optimal duration, dose, and administration interval of the treatment. Slow-release somatostatin analogue is a safe and efficacious treatment for type 1 and 2 gastric carcinoid tumors, and can be used when tumors are growing rapidly. Slow-release somatostatin analogue represents an alternative to repeated endoscopic treatment or high-risk surgery.

Mechanism of gastric mucosal proliferation induced by gastrin

Gastrin has a potent trophic effect on gastric fundic mucosa. When serum concentrations of gastrin are elevated, proliferation of both the progenitor cells in the glandular neck zone and enterochromaffin-like (ECL) cells in the bottom of the glands is stimulated. Because ECL cells have gastrin receptors, their proliferation is directly stimulated by gastrin. However, because the proliferation of progenitor cells cannot be directly stimulated (so far there has been no gastrin receptor demonstrated on these proliferating cells), some indirect mechanisms must be involved. Enterochromaffin-like and parietal cells are only two types of cells that have demonstrated a strong gene expression of the gastrin receptor. Furthermore, they secrete several growth factors, such as Reg protein, heparin-binding epidermal growth factor-like growth factor (HB-EGF) and amphiregulin (AR). Reg protein production by ECL cells, as well as HB-EGF and AR production by parietal cells, is stimulated by gastrin and these growth factors are potent trophic agents of progenitor cells in the neck zone of the gastric fundic mucosa. Accordingly, gastrin may stimulate the proliferation of gastric mucosal cells indirectly via these growth factors in addition to its direct trophic effect on ECL cells.

Induction of heparin binding epidermal growth factor-like growth factor and amphiregulin mRNAs by gastrin in the rat stomach

The present study was designed to investigate whether heparin-binding epidermal growth factor-like growth factor and its related peptides are expressed in response to gastrin in rat stomach. Rat gastrin-17I (2.5 nmol/kg/hour) or gastrin-17I plus gastrin receptor antagonist, L-740,093 (2.0 mg/kg/hour), was injected intravenously into male Sprague-Dawley rats. RNA was extracted from oxyntic mucosa, and heparin-binding epidermal growth factor-like growth factor and related peptide gene expression was estimated using a ribonuclease protection assay. The level of transforming growth factor-alpha mRNA did not change at any time point during the experiment. In contrast, the levels of heparin-binding epidermal growth factor-like growth factor and amphiregulin mRNA were significantly increased within 3 hours following gastrin infusion and reached maximum levels 6 and 12 hours later, respectively. Continuous infusion of gastrin significantly increased oxyntic mucosal proliferation. Gastrin receptor antagonist significantly inhibited gastrin-induced heparin-binding epidermal growth factor-like growth factor and amphiregulin gene expression and gastrin-induced oxyntic mucosal proliferation. These findings indicate that heparin-binding epidermal growth factor-like growth factor and amphiregulin genes are induced by gastrin and that they play a role in the trophic action of gastrin on oxyntic mucosa.

Oxyntic endocrine cells of hypergastrinaemic patients. Differential response to antrectomy or octreotide

BACKGROUND/AIMS

To evaluate the response of endocrine cells of the gastric oxyntic mucosa in hypergastrinaemic patients to either antrectomy or treatment with the somatostatin analogue octreotide.

PATIENTS

(a) Two patients with enterochromaffin-like (ECL) cell carcinoid and chronic atrophic gastritis, treated with antrectomy; (b) four patients with Zollinger-Ellison syndrome, treated with octreotide.

METHODS

Oxyntic endocrine cells were examined by ultrastructural morphometry on full thickness biopsy specimens taken: (a) before and four months after antrectomy, (b) before and after three months' treatment with octreotide 200 micrograms daily.

RESULTS

Both treatments induced prompt, significant reduction of gastrinaemia and a significant decrease of the volume density of the whole endocrine cell mass and of the cross sectional area of all nucleated endocrine cell profiles (antrectomy: -38%, p < 0.04 and -31%, p < 0.04, respectively; octreotide: -59%, < 0.007 and -26%, < 0.04, respectively). Assessment of the relative proportion of individual endocrine cell types showed a different response to antrectomy or octreotide. After antrectomy, in fact, only the volume fraction of ECL cells was significantly reduced, from 56.5% to 22.5% (-60%, p < 0.04). After octreotide treatment, in contrast, the proportion of all endocrine cell types remained remarkably constant, showing that all cell types took part in the observed overall decrease.

CONCLUSIONS

Postantrectomy reduction of oxyntic endocrine cells mostly reflects the withdrawal of the specific trophic stimulus of hypergastrinaemia on ECL cells. In contrast, the inhibitory response to octreotide seems to be exerted on virtually all types of oxyntic endocrine cells, probably reflecting a universal occurrence of somatostatin receptors.