INTERMEDIATE ENDOCRINE-ACINAR PANCREATIC-CELLS IN DUCT LIGATION CONDITIONS

When tissues were subjected to 24 h of duct ligation, intermediate pan creatic cells simultaneously displaying endocrine and exocrine phenoty pes appeared. Immunocytochemistry by laser scanning confocal microscop y revealed the appearance of a large number of these cells coexpressin g insulin and amylase. These cells were located within the islets of L angerhans as well as in the acinar parenchyma. They were also detected in a culture system of isolated pancreatic cells. With the use of imm unoelectron microscopy, two types of secretory granules were identifie d in these cells. One was insulin immunoreactive, whereas the other, r esembling zymogen granules, contained amylase. Occasionally, some smal l granules displayed a double labeling for both secretory proteins. Nu merous crinophagic bodies and autophagosomes containing insulin and/or amylase were also present. In situ hybridization, applied with the sp ecific probes, confirmed the presence of both insulin and amylase mRNA s in these cells. Because duct ligation is known to induce insulin cel l proliferation, the present results confirm that endocrine-acinar cel ls do appear in such condition and may represent intermediate steps in a transdifferentiating process.