Abstract
Actinomycin D administration to young rats provokes segregation of the nucleoli of adrenal fasciculata cells into 5 distinct zones (granular, fibrillar and vacuolar zones, a fibrillar center, and a dense fibrillar or “contrasted” zone); in the cytoplasm, there were dilations of Golgi cisternae. In spite of the nucleolar segregation, the cytoplasmic alterations suggest the maintenance of protein synthesis.