| 1. |
- Andersson, K, et al.
(författare)
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Effect of a-fluoromethylhistidine-evoked histamine depletion on ultrastructure of endocrine cells in acid-producing mucosa of stomach in mouse, rat and hamster
- 1996
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Ingår i: Cell and Tissue Research. - 1432-0878. ; 286:3, s. 84-375
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Tidskriftsartikel (refereegranskat)abstract
- The oxyntic mucosa of the mammalian stomach is rich in endocrine cells, such as ECL cells, A-like cells, somatostatin cells, D1/P cells and, in some species, enterochromaffin cells. The various endocrine cell types can be distinguished on the basis of their characteristic cytoplasmic granules and vesicles. The ECL cells contain numerous large secretory vesicles and relatively few, small electron-dense granules and small clear microvesicles. We have suggested that in the rat the ECL cells contain most of the gastric histamine with the secretory vesicles as the major histamine storage site in these cells. alpha-Fluoromethylhistidine is an irreversible inhibitor of histidine decarboxylase, the histamine-forming enzyme. We have previously shown that this enzyme inhibitor depletes histamine from the ECL cells in the rat and reduces the number of secretory vesicles in the cytoplasm. In the present study, we have examined whether alpha-fluoromethylhistidine affects the ECL cells in other species and whether it affects other types of endocrine cells in the oxyntic mucosa of the rat. Mice, rats and hamsters were treated with the inhibitor (3 mg/kg per h) via minipumps subcutaneously for 24 h. This treatment lowered the oxyntic mucosal histamine concentration by 65-90% and the number and volume density of the secretory vesicles by 85-95% in the ECL cells of the three species examined. In contrast, the number and volume density of granules and microvesicles were not greatly affected. No evidence was found for an effect of alpha-fluoromethylhistidine on A-like cells, somatostatin cells or D1/P cells of the rat stomach, suggesting that, unlike the ECL cells, they do not contain histamine.
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| 2. |
- Andersson, K, et al.
(författare)
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Enterochromaffin-like cells in the rat stomach: effect of depletion. A chemical, histochemical and electron-microscopic study
- 1992
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Ingår i: Cell and Tissue Research. - 1432-0878. ; 270:1, s. 7-13
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Tidskriftsartikel (refereegranskat)abstract
- In the rat, gastric histamine is stored predominantly in the enterochromaffin-like (ECL) cells, which are located basally in the oxyntic mucosa. The functional significance of histamine in the ECL cells is a matter of speculation. In this study the effect of depletion of histamine on the properties and ultrastructure of the ECL cells was examined. Histamine synthesis was inhibited with alpha-fluoromethylhistidine (3 mg.kg-1.h-1) given via osmotic minipumps over a period of 24 h. The treatment reduced the histidine decarboxylase activity (approximately 20% remaining) and histamine concentration (less than 20% remaining) in the oxyntic mucosa, as well as the intensity of histamine- and chromogranin A-immunostaining in the ECL cells, compared to control rats. The cytoplasmic (secretory) granules/vesicles were greatly reduced in number and size following alpha-fluoromethylhistidine administration. The histamine immunostaining of the mast cells, which occurs at the mucosal surface and in the submucosa, appeared unaffected. We conclude that ECL cell histamine accounts for at least 80% of the total oxyntic mucosal histamine in the rat and that it represents a more mobile pool than mast cell histamine. The reduction in the number and size of the ECL cell granules/vesicles following histamine depletion is in accord with the idea that they represent the storage site for histamine.
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| 3. |
- Andersson, K, et al.
(författare)
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Hyperplasia of histaime-depleted enterochromaffin-like cells in rat stomach using omeprazole and a-fluoromethylhistidine
- 1992
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Ingår i: Gastroenterology. - 1528-0012. ; 103:3, s. 897-904
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Tidskriftsartikel (refereegranskat)abstract
- In the rat, gastric histamine is stored mainly in the enterochromaffinlike cells. Gastrin releases histamine from these cells, and long-term hypergastrinemia results in hyperplasia. The effect of sustained hypergastrinemia on histamine-depleted enterochromaffinlike cells was studied by measuring histidine decarboxylase activity and histamine concentrations and by using quantitative histology. Hypergastrinemia maintained for 6 weeks was induced by inhibition of gastric acid secretion with omeprazole (400 mumol.kg-1.day-1) given orally, and histamine synthesis was inhibited for the same length of time with alpha-fluoromethylhistidine (3 mg.kg-1.h-1) given via osmotic minipumps. In rats given omeprazole alone, the effects of the resulting hypergastrinemia on the enterochromaffinlike cells was reflected in increased histidine decarboxylase activity, increased histamine concentration, and increased number of enterochromaffinlike cells. The general trophic effects on the stomach were seen as increased stomach and oxyntic mucosal weight and increased mucosal thickness. Treatment with alpha-fluoromethylhistidine plus omeprazole markedly reduced the histidine decarboxylase activity and histamine concentration, but the weight of the stomach and oxyntic mucosa, the enterochromaffinlike cell density, and intensity of histidine decarboxylase immunostaining were increased to at least the same extent as after omeprazole alone. These observations indicate that enterochromaffinlike cell histamine is not important for a full expression of gastrin-evoked trophic effects in the stomach.
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