The effects of ionizing radiation on the glycosaminoglycan synthesis in embryonic cartilage in vitro.

The effects of ionizing radiation on the glycosaminoglycan synthesis of cartilaginous tibiae of 6.5 day old chick embryos have been studied in vitro over a 3 day period. As a parameter for the glycosaminoglycan synthesis, the incorporation of (3)H-glucosamine is evaluated by liquid scintillation counting. A radiation induced inhibition ranging from 6% at 20 Gy to 68% at 200 Gy is observed. Light microscopical autoradiographs reveal that the secretion of the newly synthesized glycosaminoglycans is not affected significantly by ionizing radiation up to 150 Gy. Electron microscopical pictures confirm this observation and show that the chondrocytes in the irradiated tibiae remain viable. At 200 Gy most cells are necrotic. The results indicate that the radiation effects on the synthesis of the extracellular matrix components are determined by the damage of the RNA transcription.