Are prostaglandins cytoprotective in the human large intestine? The effect of indomethacin on rectal mucosal function and prostaglandin E2 release in vivo.

To test the hypothesis that prostaglandins are cytoprotective in the human large intestine, we investigated the effect of withdrawal of treatment with indomethacin suppositories on bowel habit and on rectal mucosal electrolyte transport and prostaglandin production in 8 patients taking such treatment for rheumatological disorders. Discontinuation of indomethacin doubled rectal mucosal prostaglandin E2 release (p less than 0.05) measured by in vivo rectal dialysis. Although there was no significant overall change in stool frequency, stool consistency, rectal bleeding or sodium absorption (also assessed by rectal dialysis), sigmoidoscopic appearance (p = 0.05), rectal mucosal potential difference (p less than 0.05) and potassium transport (p = 0.01) each reverted towards normal on indomethacin withdrawal. These results accord with the theory that, as in the upper gastrointestinal tract, prostaglandins may play a role in the maintenance of rectal mucosal structure and function.