Localization of kallikrein and its relation to other trypsin-like esterases in the rat pancreas. A comparison with the submandibular gland.

Kallikrein was located by the direct immunofluorescence technique to the granule-containing luminal portion of pancreatic acinar cells. For the demonstration of the intracellular distribution of pancreas kallikrein, in vivo fixation of the gland was necessary. No kallikrein was found in the duct cells or in the islets of Langerhans. Quantitation by single radial immunodiffusion showed that the concentration of kallikrein in the presence was 1.32 +/- 51 microgram/g wet weight, i.e. 1/91 that of the rat submandibular gland. Bz-Arg-OEt-esterases were in the pancreas found as pro-enzyme but as active enzyme in the submandibular gland. Trypsin-like esterases, hydrolyzing epsilon-amino caproic acid naphtol-AS-D.HBr (ACA), were found in the active form in both submandibular gland and pancreatic homogenates. The submandibular gland contained per g wet weight 6 times as much ACA-esterase activity as the pancreas. In the submandibular gland, kallikrein and ACA-esterase activity were found together in practically all granular tubular cells. Thus, the granular tubular cell contains kallikrein as well as other trypsin-like enzymes like the ACA-esterase, and is in this way comparable to the pancreatic acinar cell. An extraglandular function of kallikrein is suggested for the pancreas in contrast to other kallikrein-containing exocrine organs.