OBJECTIVETo investigate the effects of microwave radiation on thymocytes in mice at different power densities.

METHODSThe experimental animals were whole-body exposed to microwave radiation with frequency of 2,450 MHz, power density of 1, 5, 15 mW/cm(2) respectively 1 h everyday for 30 days. Then the thymus were taken out after the mice were decapitated. Thymus index, morphological characteristics of thymus were examined. The changes of thymus T-cell subgroups, cell cycle progression in thymocytes and cellular apoptosis were detected with flow cytometry (FCM).

RESULTSThe body weights of animals in 5, 15 mW/cm(2) irradiation groups [(28.10 +/- 1.46), (27.50 +/- 2.52) g] were lower than that of the control [(31.95 +/- 2.51) g] (P < 0.05). Pathological observation showed dark red piece of nucleus, some nuclei inclined to one side, slight increase in hassall body. The expressions of CD8 in 5, 15 mW/cm(2) irradiation groups (29.14% +/- 1.68%, 29.18% +/- 0.81%) were higher than that in control group (26.95% +/- 1.27%) (P < 0.05). The percentages of G(2) + M phase thymocytes in both radiation groups (12.24% +/- 1.82%, 11.19% +/- 1.36%) were lower than that in control group (14.58% +/- 0.64%) (P < 0.01). Thymocytic apoptosis rates in the three experimental groups (7.18% +/- 0.99%, 10.06% +/- 1.58%, 9.45% +/- 0.92%) were higher than that in control (4.25% +/- 1.63%) (P < 0.01), but the evident difference between 5 mW/cm(2) and 15 mW/cm(2) was not found (P > 0.05).

CONCLUSIONSub-chronic microwave exposure (2 450 MHz, 5, 15 mW/cm(2)) could induce thymocyte apoptosis, cause pathological changes in thymus, and affect cell cycle progression, thus may inhibit the immune function of the animal.