Objective To investigate the effects of 900 MHz microwave radiation on circadian rhythm of melatonin, testosterone, and estradiol levels in plasma of male rats.
Methods The locomotor activity of 30 adult male SD rats were measured after 30 d of adaption and fitted to a single cosine curve with a 24 h cycle for circadian rhythm screening. After that 10 out of 17 rats with similar circadian rhythm of melatonin levels in plasma were randomly divided into a control group and a radiation group (5 rats for each group). The latter was exposed to microwave radiation (2 000 μW/cm2, 900 MHz, 1 h/d, 30 d) at zeitgeber time (ZT) 1. The control group was treated in the same condition of the radiation group except radiation. Blood samples were collected from caudal vein every 4 h after the last radiation exposure. Testosterone, estradiol, and melatonin levels in plasma of blood samples were determined and fitted to phase response curves (PRCs) using a cosine model.
Results The mesor, amplitude, and acrophase of PRCs for plasma melatonin level and testosterone level showed significant differences between the control group and the radiation group (P < 0.05). The plasma estradiol levels presented significant circadian rhythm in the control group, but not in the radiation group.
Conclusion The findings indicate that 2 000 μW/cm2, 900 MHz microwave radiation can affect the circadian rhythm of plasma testosterone, estradiol, and melatonin levels in male rats.
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