目的：利用生化和完整的骨組織形態學定量分析法，探討局部性鈷六十放射線照射對骨組織的影響和其導致骨質流失的機轉。材料與方法：本研究中使用 40 隻 8 週大雄性 SD 大白鼠，按隨機抽樣法分成對照組和放射線照射組。在鈷六十放射線（ 12Gy ）局部照射於大白鼠右側股骨和脛骨。動物分別於照射後 1、7、14 或 28 天犧牲。動物犧牲後，利用血液生化分析法（鹼性磷酸?t和抗酒石酸鹽酸性磷酸?t濃度的測定）和靜態與動態骨組織形態學計量法等進行放射線局部照射後，骨生成和骨吸收各項參數的計量與分析，以及放射線照射對骨組織影響機轉的探討。結果：鈷六十放射線照射後七天時發現抗酒石酸鹽酸性磷酸?t活性，破骨細胞平均含核數和骨吸收表面顯著地增加， 而單位面積造骨細胞數目細、硬組織百分比、骨百分比、骨小樑厚度、骨小樑礦物質沈積速率及骨小樑骨生成速率則明顯地降低，在照射後 28 天則發現上述參數有逐漸回復正常之趨勢。結論：局部性鈷六十放射線照射會導致： 1 （破骨細胞平均含核數、抗酒石酸鹽酸性磷酸 @ 活性和骨吸收表面明顯遞增加和 2 ）造骨原始細胞增生、造骨細胞的活性及礦物化作用明顯地減少。 因此，局部性放射線鈷六十照射會導致骨質流失之發生。

　　　　　Purpose：To investigate the quantitative changes in bone afterlocalized Cobalt-60 irradiation （ IR ） using biochemical assay andwell-established histomorphometric analysis and the mechanisms ofirradiation-induced bone loss. Materials and Methods： Foryt 8-week old maleSprague-Dawley rats were randomly assigned into control and irradiated （ IR ）groups. Five rats of each group were sacrified at 1,7,14 or 28 days after 12 Gyof localized Cobalt-60 irradiation on right femur and tibia. The parameters ofbone formation and bone resorption, and the mechanism of IR on bone wereevaluated using biochemical bone marker assay [measuring the concentrations ofserum-alkaline phosphatase and tartrate resistant acid phosphatase （ TRAP ） ],and the static and dynamic bone histomorphometry. Results： Seven days afterlocalized cobalt-60 irradiation, there were significant increases in TRAP,nuclei/OC and resorption surface, and decreases in OB/mm ??.A significantdecrease in OC/mm ?? occurred 14 days after irradiation. In addition, OC/mm ??,nuclei/OC and resorption surface returned to normal on day 28. No significantdifference were found in percent hard tissue, percent bone, trabecularthickness, trabecular mineral apposition and trabecular bone formation betweenthe irradiated and untreated normal control group one day after irradiation.However, they became significantly less on day 7 and began to resume on the day28 after irradiation. Conclusion： Localized Cobalt-60 irradiation couldsignificantly increase nuclei/osteoclast, TRAP activity and resorption space. Inaddition, it significantly decrease osteo-progenitor cell proliferation,osteoblstic activity and mineralization, and induce dramatic bone loss. Inconclusion, Cobalt-60 irradiation could result in osteopenia. ?滋?