Cytoprotection and prostaglandins.

Among substances producing gastrointestinal cytoprotection, prostaglandins are the most potent. They protect the mucosa after either exogenous administration or stimulation of endogenous release by the stomach. The first type is called "direct" cytoprotection, and the second "adaptive" cytoprotection. Certain agents are cytoprotective by a mechanism other than endogenous formation of prostaglandins. Depletion of the gastrointestinal tract of prostaglandins by administration of nonsteroidal antiinflammatory compounds or corticosteroids can lead to ulcer formation. The mechanism of cytoprotection is unknown. It may involve stimulation of bicarbonate and mucus secretion, protection of the gastric mucosal barrier, and increase in mucosal phospholipid surfactants, and maintenance in mucosal blood flow, increase in sulfhydryl agents or increase in cellular resistance.