[Electron autoradiographic study of the synthesis of RNA in the reparative regeneration of bones].

The metabolism of RNA in cells of callus 4 and 7 days following the fracture was studied. At the three stages of differentiation of osteogenic cells--preosteoblasts, differentiating osteoblasts, and osteoblasts--there was noted a similar dynamics of synthesis and transfer of RNA. One and a half hour after administration of a precursor of RNA--uridine-5H3 grains of silver concentrated predominantly above the nuclei, nucleoli being marked most intensively. Four hours after the administration of the precursor the total number of grains above the cells increased, mostly above the granular endoplasmatic reticulum; density of grains over the nuclei at this time did not change significantly, whereas that over the nucleoli decreased notably. The relationship between the observed features of the RNA metabolism and various stages of differentiation of osteogenic cells is considered.