Abstract

The author studied the changes of pancreatic acinar cells after actinomycin D treatment to clarify the precise morphologic changes during secretory processes of the recovery stage of injured cells. Rats were given intramuscular injection of 0.5μgm of the drugs per gm of body weight. Animals were sacrificed on the next, second and fifth days after injections and observed by the electron microscope. The results were summarized as following: The pancreatic acinar cells, on the next day after actinomycin D treatment showed considerable loss of their secretory granules, shedding and destruction of membrane-bound ribosomes, and fragmentation and distortion of lamella pattern of rER with dilatation of their lumina. On the second day, rER remained in vesicular or vacuolar shape and ribosomes were enormously increased in number. Golgi complex was markedly proliferated and active secretory granules were increased in number but most were small. On the fifth day, almost entire subcellular structures were returned to normal. The results suggested that actinomycin D inhibited the secretory granule formation by blocking the protein synthesis and these changes were progressively from the second day and the recovery was completed on the fifth day.