OBJECTIVETo investigate radiation protection and possible mechanisms of low intensity microwave on gamma-ray exposed mice.

METHODS96 healthy Kunming mice were randomly divided into the following four groups: normal control, microwave (120 microW/cm(2), 900 MHz), gamma-ray irradiation (5 Gy), combined exposure of microwave and gamma-ray (120 microW/cm(2) + 5 Gy). The microwave group and combined group were exposed to 120 microW/cm(2) microwave firstly, 1 h/d, for 14 days. Then the ionization and combined group were exposed to 5 Gy (60)Co gamma-ray irradiation on the 15th day. Animals were sacrificed on the third, 6th, 9th and 12th day after irradiation. The sternum and spleen paraffin section were produced, and the histological changes were observed. Apoptosis rate of mice splenic cells in each group was examined by flow cytometry, and serum concentration of antioxidant and lipid peroxide was detected at the same time.

RESULTSBone marrow was obviously injured either by radiation or microwave exposure, characterized by undergoing four-phase lesions, namely apoptosis-necrosis, void, regeneration and recovery phase. Compared with the gamma-ray group, the pathological changes in combined group were slighter and the recovery was quicker. The pathological injuries of spleen were similar to that of bone marrow. Injuries in the combined group were slighter than gamma-ray group. It showed that apoptosis rate of splenic cells in combined group was significantly lower on the 6th and 9th day after gamma-ray radiation (23.02% +/- 15.18%, 25.37% +/- 11.62% respectively) from FCM results. Assays of oxidative damages suggested that serum superoxide dismutase (SOD) level in combined group increased while lipid peroxide level decreased significantly (P < 0.05).

CONCLUSIONLow intensity microwave may exert protection effects on injuries induced by ionizing radiation. The underlying mechanisms might be related with suppression on the hematopoietic cells apoptosis induced by gamma-ray radiation, inhibition of oxidative damages, and thus enhanced reconstruction of the hematopoietic system.