Pancreatic damage induced by injecting a large dose of arginine

Male Wistar rats were injected intraperitoneally with a large dose of arginine (500 mg/100 g body weight) and were sacrificed 24, 48 and 72 h later. Pancreatic tissue was examined by electron microscopy to study the resulting process of degeneration. Degeneration started with disorganization of the rough endoplasmic reticulum into whorls with a concomitant decrease in the numbers of zymogen granules. The main changes in acinar cells after 24 h were partial distension of the endoplasmic reticulum, whorls of agranular membranes encircling zymogen granules and perinuclear vacuoles. At this time large sequestered areas in the cytoplasm contained disarranged rough endoplasmic reticulum and degraded zymogen granules. The mitochondria showed only slight changes. After 48 h, dissociation and necrosis of acinar cells were noted. Subsequently, the necrotic cells were replaced by interstitial tissue composed of leucocytes and fibroblasts. It was concluded that a large dose of arginine is toxic to the rat pancreas when injected intraperitoneally. The early morphological changes of the acinar cells may be related to metabolic alterations associated with the endoplasmic reticulum. The disorganization of the endoplasmic reticulum and the reduced number of zymogen granules may indicate disturbance of protein synthesis. The focal sequestration and degradation of the cytoplasm seemed to represent changes of the acinar cells associated with removal of damaged organelles.