Pancreatic injury caused by intraductal injection of foreign serum in rat

Abstract

One ml of either fresh or heat-inactivated (56° C., 30 min) normal (nonimmunized) rabbit serum was injected into rat pancreas through a needle inserted into the common biliary-pancreatic duct. The animals were killed and pieces from the pancreas were processed for electron microscopy 30 min, 1, 3, 6, 12 and 24 h after the injection of fresh serum as well as 3 and 24 h after the injection of heat-inactivated serum. The endoplasmic reticulum and the mitochondria were swollen and disorganized at the early stages of the cell injury response. Later changes seen in these organelles were vesiculation and loss of ribosomes, and degeneration of cristae and deposition of dense granular material in the mitochondrial matrix, respectively. The zymogen granules showed minimal changes only. At late time intervals there were large sequestered remnants of necrotic cells, consisting of membranous, granular, and vacuolated components, in the cytoplasm of atrophic acinar and endocrine cells. There were no pathologic changes in the pancreases injected with heat-inactivated serum. It was concluded that fresh rabbit serum is toxic to rat pancreas when injected into the common biliary-pancreatic duct. The injury is most probably caused by the complement of the injected serum. The ultrastructural changes reflect rapid membrane damage leading to loss of volume control, death, and necrosis of affected acinar cells.