21. Gastrin acts on parietal cells directly and indirectly too, by stimulating the release of histamine.22. Increased gastrin secretion also leads to peptic ulcers in > 50 % of MEN 1 patients. 23. The hydrogen potassium ATPase is activated indirectly by gastrin that causes ECL cells to release histamine. 24. Reduced gastrin secretion reduces acid secretion. 25. This results in an elevated gastrin level in an attempt to compensate for increased pH in the stomach. 26. Increased gastrin secretion increases gastric acid, which may inactivate pancreatic lipase, leading to diarrhea and steatorrhea. 27. The excitation of the vagus nerve, the administration of gastrin , secretin or cholecystokinin induce PP secretion. 28. Gastric secretion is stimulated chiefly by three chemicals : acetylcholine ( ACh ), histamine, and gastrin . 29. Gastrin stimulates acid secretion by directly stimulating parietal cells as well as by promoting histamine secretion by ECL cells.30. The chief cells secrete pepsinogen in response to gastrin and especially Ach, and ACh also stimulates mucus secretion.
