3.25 in. x 4 in. Lantern Slides, Original Magnification: x2,000, and This study demonstrated directly that the enzyme and proenzyme composition of proteins in pancreatic juice collected from an indwelling catheter in the bovine pancreatic duct correlated exactly with the protein composition obtained from lysed purified bovine zymogen granules. Subsequent studies showed that pancreatic digestive enzymes and proenzymes were secreted from the pancreas in parallel. In other words, each granule must contain, on average, the same composition of secretory proteins. This hypothesis was later directly tested by immuno-EM localization of trypsinogen and other secretory proteins in all zymogen granules in the bovine pancreas.
