Introduction
Figure 1. Chemical structure of pentagastrin
Pentagastrin, known as peptavlon, is a synthetic pentapeptide that promotes the secretion of gastric acid, pepsin and internal factors. The faculty of pentagastrin to improve gastric acid secretion is equivalent to one quarter of the natural gastrin, even stronger than histamine phosphate and amidoeprazole hydrochloride. Pentagastrin are mainly used for the examination of gastric secretion function and pancreatic function.
Pharmacologic action
Pentagastrin stimulates the secretion of gastric acid, pepsin and internal factors. However, the exact mechanism of action remains unclear. In fact, as an analogue of natural gastrin, pentagastrin stimulates the secretion of the oxyntic cells in the stomach to a maximum capacity. Pentagastrin also promotes the pancreatic secretion, especially at large intramuscular doses. In order to enhance the gastrointestinal motility, pentagastrin works on the intestinal smooth muscle directly. Furthermore, through the stimulation of terminal antral contractions, the delay of gastric emptying time is achieved, thereby enhancing the retropulsion.
Function
On the one hand, pentagastrin serves as a diagnostic aid to evaluate the secretion function of gastric acid. For patients with suspected pernicious anemia, atrophic gastritis or gastric carcinoma, it is relatively effective to check for achlorhydria. In addition, pentagastrin works on detecting the reduction in acid output after operations for peptic ulcer, such as vagotomy or gastric resection. On the other hand, pentagastrin is considered to be a diagnostic assistance to test for gastric hypersecretion in patients with suspected duodenal ulcer or postoperative stomal ulcer, and the diagnosis of Zollinger-Ellison tumor.
Pharmacokinetics and metabolism
Pentagastrin administration leads to the diminution of histamine content in the oxyntic gland mucosa, and this change is numerically large in patients with duodenal ulcer disease. Pentagastrin induces a soar in histidine decarboxylase activity of the oxyntic gland mucosa with the most profound increase observed in patients with duodenal ulcer. For patients with Zollinger-Ellison syndrome, the oxyntic mucosa occurs high-rate histamine formation. The activity of histamine methyltransferase is not affected by pentagastrin. In conclusion, histamine is only activated in large amounts from the oxyntic gland mucosa after pentagastrin administration, especially in patients with duodenal ulcer disease.
References:
1.Lönroth, H., Rosengren, E., Olbe, L., Lundell, L. Histamine metabolism in human gastric mucosa. Effect of pentagastrin stimulation. Gastroenterology, 1990, 98(4): 921-928.
2. Lind, T., Cederberg, C., Ekenved, G., Haglund, U., Olbe, L. Effect of omeprazole--a gastric proton pump inhibitor--on pentagastrin stimulated acid secretion in man. Gut, 1983, 24(4): 270-276.
3. Maejima, R., Koike, T., Nakagawa, K., Iijima, K., Shimosegawa, T. Esomeprazole inhibits the pentagastrin-stimulated secretion of gastric acid in healthy Japanese volunteers. The Tohoku journal of experimental medicine, 2015, 235(3): 249-253.
4. Thiem, U., Marculescu, R., Cejka, D., Gessl, A., Borchhardt, K. Low-dose calcium versus pentagastrin for stimulation of calcitonin in chronic hemodialysis patients: a pilot study. The Journal of Clinical Endocrinology & Metabolism, 2014, 99(12): 4704-4711.
