Luminal processing of epidermal growth factor in mouse gastrointestinal tract in vivo

To test the stability of epidermal growth factor (EGF) in the gastrointestinal lumen 125I-labeled EGF was administered to the lumen of isolated stomach, duodenum, jejunum, midjejunum, and ileum of anesthetized mice (14-day-old neonatals and 8-week-old adults). Radioactivity extracted from luminal contents and tissues of gastrointestinal segments was analyzed by binding to C18 isolation cartridges followed by reversed-phase high performance liquid chromatography (RP-HPLC). At 10 min, 74-97% of administered radioactivity was present in the isolated segments (luminal contents + segment tissue). Major portions (60-88%) of radioactivity recovered from luminal contents and segment tissues bound to C18 cartridges, except for lower values (40-54%) recorded in segment tissues of adult mice. RP-HPLC identified > 90% of C18-extracted radioactivity from gastric luminal contents of neonatal and adult mice as intact [125I]EGF (30-min retention time). In adult mice, 46-51% of radioactivity extracted from midjejunal luminal contents was identified as intact [125I]EGF, whereas only 3-5% was intact [125I]EGF in neonatal mice. On the contrary, in extracts of duodenal, jejunal, and ileal luminal contents, 14-30% of radioactivity was intact [125I]EGF in neonatal mice, whereas < 3% was intact [125I]EGF in adult mice. Considerable amounts of intact [125I]EGF were present in the adult mouse gastric tissue and neonatal mouse gastric and duodenal tissues. The remainder of C18-extracted radioactivity from different luminal contents and segment tissues eluted as three major C-terminally truncated EGF derivatives. These three [125]EGF derivatives, eluted with retention times of 35, 21, and 24 min, respectively, were identified as 125I-labeled EGF(1-52), EGF(1-48), and EGF(1-47).(ABSTRACT TRUNCATED AT 250 WORDS)