Distribution of prostaglandin E2 binding sites in the porcine gastrointestinal tract

Binding of biologically active 3H-PGE2 to particulate fractions of porcine gastrointestinal mucosa and muscle was investigated. Specific binding activity was detected in the 2500 xg and 30,000 xg sedimentation fractions of mucosa from esophagus, fundus, antrum, duodenum, ileum and colon, as well as in serosal muscle taken from the antrum, ileum, and colon. Optimal binding (greater than 40 fmol/mg protein) was observed in the 30,000 xg fraction of fundic mucosa incubated at pH 5.0. The characteristics of 3H-PGE2 binding were variable in the remainder of the gastrointestinal tract although binding in these tissues was significantly less (0.2 to 15 fmol/mg protein) than that observed in the fundic mucosa. These data suggest that the cellular and/or subcellular site of PG binding is not uniform throughout the gastrointestinal tract. In fundic mucosa removal of the surface epithelial layer by scraping did not significantly alter the total binding activity for PGE. This result suggests that in gastric secretory mucosa optimal binding activity for PGE2 occurs within the gastric pits deep to the surface epithelium.