Abstract: Objective To observe the morphological changes of pancreatic tissue of thoracic duct ligated rats in fine and ultrastructural levels, and to determine whether lymph block animal model can affect pancreatic islet amyloid polypeptide（PIAP）deposit in rat pancreas. Methods At the 6th month after the operation, some pancreatic tissue sections of 16-month-old experimental rats were embedded in paraffin wax and stained with HE and Congo red; immunohistochemical staining was performed on some frozen sections, which were then observed with light microscope; transmission electron microscope (TEM) specimen preparation and observation were performed on other samples. Results HE and Congo red stained sections showed that the pancreatic glandular lobule space was widened, with significant connective tissue hyperplasia, and fat accumulation when the islet was stained indistinctly or vermeil and tissue space was broadened. The sections with immunohistochemical staining displayed the pancreatic islet as well as the tissues around it were stained into dark brown being positive with PIAP antigen. TEM observation showed the pancreatic glandular interlobule space was widened, while blood vessels and enlarged lymphatic vessels were visible; within widened pancreatic islet interstitial space, a great quantity of lipid droplets and some collagen fibril structures could be seen.Conclusion The ligation of thoracic duct can contribute to pancreatic lymph draining block, lymphagiectasis, connective tissue space and interstitial space widening, fat accumulation, and PIAP deposit in rat pancreas. These structural changes may affect the function of pancreatic islets.

Key words: Pancreatic tissue, Lymphatic vessel, Pancreatic islet amyloid polypeptide, Immunohistochemistry, Transmission electron microscopy, Rat