The decay of endogenously labelled 75Se-selenomethionine labelled proteins in duodenal juice: evidence for recirculation in man.

The decay of the specific radioactivity of duodenal juice proteins, endogenously labelled with 75Se-selenomethionine has been studied in man. Duodenal juice was collected against a background infusion of cholecystokinin-pancreozymin (1 unit/kg/hr) and secretin (1 unit/Kg/hr). In 4 subjects, duodenal juice was aspirated continuously and pooled in 30 min. aliquots. In 3 other subjects approximately 5-10 ml of juice was removed at 15 min, intervals. The rate of decay of protein specific radioactivity was significantly more rapid in the drainage group (p less than 0.01). A similar trend was also observed for trypsin. The data suggests that endogenous duodenal juice proteins might be recirculated as intact proteins in man.