Radiation effects on the matrix synthesis in non-ossifying embryonic cartilage in vitro: a functional and morphological study.

Radiation effects on collagen and glycosaminoglycan (GAG) synthesis were studied in non-ossifying embryonic chick cartilage, in vitro. Fragments of the non-calcifying region of 15-day-old chick sterna were irradiated with 20, 50 and 100 Gy. The counterparts served as controls. Fragments were cultured up to 14 days. Pulse labeling experiments with 3H-proline and 3H-glucosamine started immediately after irradiation and on day 3, 6 and 13 post-irradiation. Fragments for morphological evaluation were fixed on day 1, 4, 7 and 14, simultaneously with the end of the labeling period. The same dose- and time-dependent inhibition was observed for the collagen and GAG synthesis. Radiation doses of 20, 50 and 100 Gy cause respectively and inhibition of about 20, 35 and 60% at the end of the culture period. Morphological alterations were observed after radiation doses of 50 and 100 Gy. Dose- and time-dependent necrosis all over the sternum was observed. A restricted number of cells showed an increased GAG synthesis after irradiation (50 Gy). This could explain the levelling off of the radiation effect on the incorporation of the labeled precursors towards the end of the culture period for radiation doses up to 50 Gy.