RADIATION-INDUCED APOPTOSIS IN RELATION TO ACUTE IMPAIRMENT OF RAT SALIVARY-GLAND FUNCTION

Purpose: To find an answer to the question: Are the acute radiation ef fects on salivary gland function, as seen in earlier studies, causally related to radiation-induced apoptosis? Materials and methods: Rat pa rotid and submandibular glands were X-irradiated with doses up to 25 G y and morphological damage assayed up to 6 days after irradiation. Dam age to the different cell types in the glands was assessed after H & E staining. Apoptotic appearance was judged by compacted chromatin and fragmentation of cells into lobulated masses. Results: In about 3% of the cells aberrant nuclei were observed after doses as low as 2 Gy and around 7.5 and 24 h after irradiation. About half of these aberrant n uclei had an apoptotic appearance. After a dose of about 5 Gy no dose- response for apoptotic cells was found, as evidenced by a plateau in t he dose-effect curve. At 6 days after 2 Gy, no signs of radiation-indu ced apoptosis was apparent and for most cell types a value close to ze ro was observed. Conclusions: Radiation studies on salivary function i n the rat show the typical response with respect to;lose (5-15 Gy) and time (1-3 days). This differs from reported findings with light micro scopy. Therefore, the extent of apoptotis induced by radiation cannot explain the observed gland malfunction. Alternative mechanisms are pro posed.