doi: 10.3967/bes2020.079
Dose-dependent Cardiac Dysfunction and Structural Damage in Rats after Shortwave Radiation
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Abstract:
Objective To detect the effects of shortwave radiation on dose-dependent cardiac structure and function in rats after radiation and to elucidate the mechanism of shortwave radiation induced cardiac injury to identify sensitive indicators and prophylactic treatment. Methods One hundred Wistar rats were either exposed to 27 MHz continuous shortwave at a power density of 5, 10, and 30 mW/cm2 for 6 min or undergone sham exposure for the control (the rats had to be placed in the exposure system with the same schedules as the exposed animals, but with an inactive antenna). The Ca2+, glutamic oxaloacetic transaminase (AST), creatine kinase (CK) and lactate dehydrogenase (LDH) content in the peripheral serum of the rats were detected by an automatic blood biochemical analyser. The electrocardiogram (ECG) of standard lead II was recorded by a multi-channel physiological recording and analysis system. The cardiac structure of rats was observed by light and electron microscopy. Results The results showed that the 5, 10, and 30 mW/cm2 shortwave radiation caused a significant increased in the levels of Ca2+, AST, CK, and LDH in the peripheral serum of rats. The cardiac structure was damaged by radiation and showed a disordered arrangement of myocardial fibres, the cavitation and swelling of myocardial mitochondria. These injuries were most significant 7 d after radiation and were not restored until 28 d after radiation. Conclusion Shortwave radiation of 5, 10, and 30 mW/cm2 can damage rat cardiac function, including damage to the tissue structure and ultrastructure, especially at the level of the myocardial fibres and mitochondria. Shortwave radiation at 5, 10, and 30 mW/cm2 induced damage to rat heart function and structure with a dose-effect relationship, i.e., the greater the radiation dose was, the more significant the damage was. -
Key words:
- Shortwave /
- Rat heart /
- Function /
- Structure /
- Damage effect /
- Dose dependence
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Figure 1. The shortwave radiation device and a schematic diagram of the radiation method[19].
Figure 3. Changes in the Ca2+ concentration and myocardial enzymes in the peripheral serum of rats after shortwave radiation. (A) Five rats were taken from each group at each time point. Blood was taken from the abdominal main vein after anaesthesia. Changes in the Ca2+ concentration in the peripheral blood were detected by an automatic biochemical analyser on 1 d, 7 d, 14 d, and 28 d after radiation. (B–D) Five rats were taken from each group at each time point. The contents of AST, CK, and LDH in the peripheral blood were detected by an automatic biochemical analyser on 1 d, 7 d, 14 d, and 28 d after radiation. Compared with the 0 mW/cm2 group, *P < 0.05, **P < 0.01.
Figure 4. Changes in the electrocardiogram in rats after shortwave radiation. (A–D) At each time point, 5 rats were taken from each group. After mild anaesthesia, the hair of the left forelimb and the right hind limb was shaved. Needle fishhook electrodes (pierced subcutaneously) were placed on the inner skin of the left forelimb and the right hind limb. Changes in the heart rate, R wave, P wave and T wave amplitude were recorded by a multi-channel physiological recorder on 1 d, 7 d, 14 d, and 28 d after radiation. Compared with the 0 mW/cm2 group, *P < 0.05, **P < 0.01.
Figure 5. The basic pathological changes associated with cardiac injury in rats after shortwave radiation (scale bar = 50 µm). On the 7 d after radiation, five rats in each group were euthanized after anaesthesia. (A) The cardiac structure in the 0 mW/cm2group; (B) The cardiac structure in the 5 mW/cm2 group; (C) The cardiac structure in the 10 mW/cm2 group. (D) The cardiac structure in the 30 mW/cm2 group.
Figure 6. Changes in the cardiac tissue structure in rats exposed to 30 mW/cm2 shortwave radiation (scale bar = 25 µm). On 1 d, 7 d, 14 d, and 28 d after radiation, five rats in each group were euthanized after anaesthesia. (A) The cardiac structure in the 0 mW/cm2 group. (B) The changes in the cardiac tissue structure in rats of the 30 mW/cm2 group 1 d after radiation. (C) The changes in the cardiac tissue structure in the 30 mW/cm2 group 7 d after radiation. (D) The changes in the cardiac tissue structure in the 30 mW/cm2 group 14 d after radiation. E: The changes in the cardiac tissue structure in the 30 mW/cm2 group 28 d after radiation.
Figure 7. The basic pathological changes associated with ultrastructural damage in the rat heart after shortwave radiation (TEM scale bar = 500 nm). On 7 d after radiation, three rats in each group were euthanized after anaesthesia. (A) The ultrastructure in the 0 mW/cm2 group. (B) Ultrastructural changes in the 5 mW/cm2 group. (C) Ultrastructural changes in the 10 mW/cm2 group. (D) Ultrastructural changes in the 30 mW/cm2 group.
Figure 8. Changes in the cardiac tissue ultrastructure in rats exposed to 30 mW/cm2 shortwave radiation (TEM scale bar = 500 nm). On 1 d, 7 d, 14 d, 28 d after radiation, three rats in each group were euthanized after anaesthesia. (A) Changes in the myocardial fibres. (B) Mitochondrial changes. (C) The changes of the intercalated disc. (D) Autophagy changes. (E) Changes in the myocardial cells. (F) Interstitial changes.
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