EFFECTS OF IONIZING-RADIATION ON THE SIZE DISTRIBUTION OF PROTEOGLYCAN AGGREGATES SYNTHESIZED BY CHONDROCYTES IN AGAROSE

Effects of ionizing radiation on the structure and size-distribution o f newly synthesized proteoglycan aggregates are studied in-vitro. Chon drocytes, isolated from embryonic chick sterna, are cultured for 7 day s in a tri-dimensional agarose system. Single radiation doses of 10, 2 0 and 50 Gy are given before starting the culture. Digestion of the ar tificial agarose matrix liberates the newly synthesized proteoglycans. Spreading with cytochrome C allows electron microscopic investigation s of the individual, newly synthesized molecules. The structure of agg regates synthesized by control and irradiated chondrocytes is comparab le, However, radiation causes alterations in the size-distributions of the aggregate-populations. For the control cultures, an average aggre gate contains 27 aggrecans per aggregate. 34 pro mille of the molecule s contain more than 100 aggrecans per aggregate. Irradiation with 10 G y doesn't cause alterations. With radiation doses of 20 and 50 Gy, an average molecule contains 20 aggrecans. Only about 9 pro mille of the aggregates contain more than 100 aggrecans. Stimulation of lysosomal a ctivity after irradiation could explain the observed alterations.