Effect of irradiation on early enzymatic changes in healing mandibular periosteum and bone. A histochemical study on rats.

The influence of irradiation was studied histochemically in healing mandibular periosteum and bone. After a cut line had been made on both sides of the mandible the rats were exposed to roentgen ray irradiation. The single doses were 15, 20, 30, 35 or 40 Gy. The animals were killed 1, 2, 4, 8, 10, 12, 16 and 24 hours after irradiation, for histochemical analysis. All enzymes, acid phosphatase, cytochrome oxidase, lactate, isocitrate, glucose-6-phosphatase and succinate dehydrogenase, showed a greater increase in enzyme staining in the irradiated cut lines than in the non-irradiated control lines. The intensity of the staining increased with time and dose over 24 hours. The observation time included an inflammatory phase with vascular, enzymatic and cellular responses to periosteal and bone injury. The increase in staining was dependent on the time after surgical trauma and radiation dose. The increase in enzyme staining probably represents the initial cell damage after irradiation.