| In this paper, we systematically investigated damage of the skin, damage and repairing of the heart tissue by optical microscopy and electron microscopy after local radiation of the power density of 7.5W/cm2 of 35GHz millimeter-wave on the back of SD male rats with different time.Firstly, we observed rat skin tissue damage after local radiation with different duration time, including 0s,5s,10s,15s,20s,30s,50s. HE staining results showed that:after 5s irradiation, the skin surface temperature was about 30℃; the surface of the skin became red swelling, but failed to wound. After 15s irradiation, the epidermal tissue appeared slightly eosinophilic red dye, cavities appeared near the hair root in the dermis with uneven distribution. However, no significant changes were observed in subcutaneous tissue. After 30s irradiation, skin damage extended to subcutaneous tissue. After 50s irradiation, burning sites emerged on the skin where the subcutaneous tissue were ruined and could not renew.Secondly, we investigated the influences on biochemical index of rats'blood after 8-millimeter local irradiation with different time, including 0s,5s,10s,15s,20s,30s,50s. The results showed that the concentration of AST, LDH, CK changed with the varies of radiation dose and sampling time. These three enzymes are functional units to the heart, liver. These changes suggests heart, liver, skeletal muscle and other organs might be hurt after 35GHz millimeter-wave local radiation with certain times.Finally, we discussed the cardiac heat stress-induced damage and repairing due to HPMMW radiation with different time, including 0s,5s,10s,20s,30s,60s,180s. The results showed that the myocardial cells damages observed by optical microscope were in different levels---blurred the boundaries between cells, myocardial cells deformation, cell necrosis. The damage became worse with an increased irradiation time. The myocardial cells damage observed by electron microscope varied as well. With a longer irradiation time, the muscle fibers tended to be more twisted, mitochondria more swelled. And the outer membranes began to dissolve. Crest damages and cavitations began to appear. The results suggest that high-power millimeter wave irradiation may damage rats'heart. It might be the reason for the rat death that was irradiated by local high power millimeter wave for several minutes. After short time irradiation(less than 180s), the recovery of heart damage was different. The recovery time was closely related to the radiation dose. The shorter time a rat irradiated, the faster it recovered. A lot of researches focus on the effects of electromagnetic radiation on heart, but they concentrated in the cm-band. The damage research of heart due to millimeter-wave irradiation is rare. Millimeter-wave as a source of heat stimulation, our studies showed that high-power millimeter-wave local radiation heat-pain stress can damage cardiac of rats. Our studies provided experimental evidence for the safe use and effective protection of high-power millimeter-wave devices.Many researches focus on the effects of electromagnetic radiation on heart in cm-band. The damage research of heart due to millimeter-wave irradiation is rare. Millimeter-wave, as a source of heat stimulation, the researches in this paper showed that high-power millimeter-wave local radiation heat-pain stress was able to damage rat hearts. Experimental evidences for the safe use and effective protection of high-power millimeter-wave devices were provided in this paper.
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