Measurement of Prostaglandin E₂ in Interstitial Fluid From the Dog Stomach After Feeding and Indomethacin

The purpose of the study was to develop a method for collecting interstitial fluid bathing the stomach tissues in which prostaglandins could be measured. Hollow dialysis fibers attached at the ends to Silastic tubes were surgically implanted into the submucosa of the gastric fundus and antrum of dogs. The Silastic tubes were exteriorized through the body wall. After full recovery from surgery, the fibers were filled with 5% bovine serum albumin in isotonic saline that was replaced at 5-min intervals. Prostaglandin E₂ was measured in the dialysate by radioimmunoassay. In 6 dogs, feeding significantly stimulated the release of prostaglandin E₂ into the fundic interstitial fluid from 5.3 ± 0.6 ng · ml^-1 to 12.1 ± 1.6 ng · ml^-1 (p < 0.01) but had no effect on antral levels. In 4 dogs, indomethacin (0.01, 0.1, 1.0, and 10.0 ng · kg^-1, i.v.) caused a dose-dependent depression in prostaglandin E₂ levels in interstitial fluid of the fundus and antrum. In 4 other dogs, indomethacin depressed the ex vivo generation of prostaglandin E2 in biopsy specimens of the fundus and antrum. These results validate the technique of interstitial fluid dialysis and suggest that it is a powerful method for examining the secretion of locally acting substances in the stomach of conscious animals.