Recovery of pancreas from mild puromycin-induced injury. A histologic and ultrastructure study in rats.

Pancreatic acinar cells undergo degeneration or necrosis following injection of puromycin intraperitoneally in rats. The purpose of this study was to characterize recovery following injection of four hourly doses of puromycin, 40mg/kg of body weight, examining the pancreas histologically and by electron microscopy. The number of dividing acinar cells increased following injury. By 12 to 24 hours following treatment, electron microscopy showed numerous autophagic vacuoles and intracisternal granules in the cells. By 48 hours, these were largely cleared from surviving cells although the intracisternal granules persisted in isolated acinar cells as long as 144 hours. At 24 hours, there was debris in the acinar lumens and interstitial space. We conclude that some acinar cells injured by puromycin may survive and be restored to normal structure; that surviving acinar cells can extrude autophagic vacuoles; and that necrotic acinar cells are replaced by regeneration following puromycin-induced injury in rats.