PURPOSE: It is well recognized that apoptosis is important in embryonic development, homeostatic control of normal tissues, carcinogenesis, tumor development and cancer therapy. Several papers have been reported the phenomenon of radiation-induced apoptosis and suggested its potential relevance to cancer radiotherapy. It has been shown that apoptosis is regulated by various cytokines. But the relationship between radiation induced apoptosis and cytokines have not fully understood in detail, yet. MATERIALS AND METHODS: In this study, we performed to determine the role of cytokine in the radiation -induced apoptosis of rat's small intestine. The rats were divided into 6 groups according to the sacrifice day (1, 2, 3, 5, 7, 14 days) after whole body irradiation with single dose of 8 Gy. RESULTS: Radiation induced intestinal damage was noted from first day of radiation and the most active regeneration was seen in the groups of 5 days after radiation. Abundant apoptosis were observed in damaged crypts of small intestine 1 day after radiation. Afterwards, the number of apoptosis was gradually diminished, but the second peak of apoptosis was noted in 5 days after radiation. On immunohistochemical study, IL-1, and TNF were expressed 1 day after radiation, but not expressed after that. IL-6 was expressed with strong positivity in 1, 3 days after radiation. CONCLUSION: A apoptosis seems to be the important mechanism of radiation induced small intestinal damage, and is possibly induced by the release of cytokines, such as IL-1, IL-6, TNF, in view the simultaneously increased appearance of apoptosis and cytokines. The second peak of increased apoptosis is thought to be related to remodeling of active regenerative activity, and it is not associated with cytokine expression.
Animals ; Apoptosis* ; Carcinogenesis ; Cytokines* ; Embryonic Development ; Female ; Interleukin-1 ; Interleukin-6 ; Intestine, Small* ; Pregnancy ; Radiotherapy ; Rats* ; Regeneration ; Whole-Body Irradiation