Asynchronous secretion of newly synthesized pancreatic proteins in the rat

The secretion of newly synthesized pancreatic proteins was studied in conscious rats with cannulated pancreatic ducts. Labeled amino acids (3H-leucine and 14C-amino acid mixture) were injected intravenously. The proteins of the pancreatic juice were separated by gel electrophoresis, and the radioactivity in each band was determined. An early secretion of labeled trypsinogen and chymotrypsinogen was found, whereas amylase and lipase were secreted after a certain lag period. In vitro pulse chase experiments showed that amylase was synthesized in the acinar cell but did not move with the same efficacy to the zymogen granules and into the pancreatic juice as proteases.