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Prostaglandins (PGs) are a group of 20-carbon oxygenated fatty acids that are present in most mammalian cells and tissues. Although their highest concentration is found in seminal fluid, the gastrointestinal mucosa contains relatively large amounts. Prostacyclin () is the most abundant PG formed by the gastric mucosa. It was suggested that and also present in the mucosa, may affect the regulation of gastric blood flow and acid secretion.
Some PGs affect gastrointestinal functions. , , and as well as certain methyl analogs of inhibit gastric secretion in animals and humans, prevent ulcer formation in animals, and reportedly accelerate ulcer healing in humans. The antiulcer effect is presumed to be due to the antisecretory activity of these compounds.
A property of PGs was discovered, called "cytoprotection" which designates the property of many PGs to protect the mucosa of the stomach and the intestine from becoming inflammed and necrotic, when this mucosa is exposed to noxious agents. This property is separate, and unrelated to gastric secretion.
Summary of the observations that led to the concept of cytoprotection and its mechanism has collected here:
1. PGs may stimulate mucus secretion. Some evidence suggests that certain PGs stimulate synthesis and release of gastric mucus. Newly formed mucus could provide a physical shield against irritants found in the gastric lumen.
2. PGs may affect the sodium pump. Sodium is normally transported from the mucosal side of gastrointestinal mucosal cells to the serosal side. The property of PGs in stimulating the sodium pump was proposed as a possible mechanism for cytoprotection.
3. PGs may activate adenylate cyclase. Several PGs stimulate adenylate cyclase activity in the gastric mucosa of several species. stimulates formation of cyclic AMP in nonparietal cells, these nonparietal cells originate from the surface epithelium, where cytoprotections take place.
4. PGs may act on the gastric mucosal circulation. Several PGs affect blood flow may explain the cytoprotective effect of .
5. PGs may protect the gastric mucosal barrier. Several PGs of the E type as well as were shown to protect the gastric mucosal barrier. Cytoprotection may result from a tightening of the gastric mucosal barrier.
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