In the present study, it was found that prolonged time (2-3 over per day) of exposure to 2100 MHz electromagnetic waves could cause changes in the level of testosterone hormone, increase the number of dead sperms and promote apoptosis in the testes. In the same way, Berg in 1999 reported that the intensity, duration of exposure, and frequency of waves are three important factors for the effects of electromagnetic waves on cellular function [4, 20], which is compatible with the present study.
Various and sometimes contradictory results have been reported on the effects of electromagnetic fields on testosterone levels. The present study showed that exposure to the electromagnetic field could significantly decrease (P≤0.004) the testosterone levels of the experimental groups (60 and 120 min). Interestingly, a remarkable increase was observed in testosterone level in the 180 min group compared to 60- and 120-min groups of exposure, although it was still lower than the control group value. It is possible that after 120 minutes, due to the severe reduction in testosterone, a rise in the LH production by the pituitary gland caused by the effect of electromagnetic waves on the CNS occurs alongside a negative feedback mechanism, which stimulates the Leydig cell to increase the testosterone hormone [21] further.
Al-Akhras et al. reported a significant increase in the serum levels of luteinizing hormone (LH) only after 18 weeks of exposure (P <0.005) [22].
Given that a series of testicular Leydig cells died by 2100 MHz electromagnetic waves, the serum level of testosterone in the 180 min group was lower than in the control group. Also, prolongation of the duration of exposure of rats affected by 2100 MHz electromagnetic waves increased the percentage of dead sperm cells, according to a report by Desai and Al-Akhras et al. [22, 23]. The reason behind the increased percentage of dead sperm cells could be mitochondrial, DNA, and nuclear destruction of sperm cells [23].
Ozguner et al. in 2005 reported that serum total testosterone level decreased significantly in the EMF group (p<0.05) [24], and Al-Akhras et al. reported testosterone levels were significantly decreased after 6 and 12 weeks of the exposure period [22] which was similar to 60 min and 120 min groups in our study. However, Al-Akhras et al. reported that no significant changes in testosterone levels were observed after 18 weeks in adult rats exposed to an electromagnetic field (50 Hz) [22] consistent with this finding, we observed that the testosterone level rose at 180 min in comparison with the 60 min and 120 min groups but in comparison with the control group decrease but the decrease was not significant.
Our results indicated that a high-frequency electromagnetic field (2100 MHz) negatively affects sperm parameters such as motility and viability characteristics (Figure 2 and Figure 3). An increase in the duration of exposure to electromagnetic waves (2100 MHz) by rats may ultimately lead to the destruction of the mitochondria and the epidermis's sperm nucleus. There may be a reason for the increase in the percentage of dead sperm cells. Figure 3 indicated that sperm motility significantly decreased in the experimental groups (60, 120, and 180 min). In addition, Figure 2 revealed that sperm viability diminished significantly across all experimental groups after 70 days of exposure (P≤0.05). Also, our result is in line with Baharara et al. [25] findings obtained in 2015 (50 Hz), Hamdi [26] (50 Hz), De Iuliis et al. [27] (Mobile phone radiation), Deepinder et al. [1] (radio-frequency), and Erogul et al. [28] (900 MHz) who reported diminished sperm motility.
In another study, Yan et al.'s results suggested that rats exposed to 6 hours of daily cellular phone propagation for 18 weeks exhibited a significantly higher incidence of sperm cell death than the control group rats did through chi-squared analysis. In addition, abnormal clumping of sperm cells was present in the rats exposed to cellular phone emissions while absent in control group rats [6]. The report of Yan results in increasing the meaning of dead sperm cells is consistent with the present study.
Apoptosis is a physiological process of selected cell elimination. As an antagonist of cell proliferation, apoptosis contributes to keeping the cell number in testicular tissue and helps to delete superfluous and damaged cells [29].
The studies of Kesari et al. [30] (Testes of rat) and Kafaee Razavi et al. [5] (rat brain
tissue) showed a significant rise in apoptosis across all experimental groups exposed to electromagnetic waves at a high frequency. Although the duration and the intensity of the electromagnetic field in the experimental groups were different, their results have been similar to ours.
The present study showed that an electromagnetic field of a new generation of mobile phone (2100MHz) increased apoptosis in spermatogenesis as well as the activity of caspase 3, which is congruent with Kesari et al. (2.45 GHz), who found Using flow cytometry a significant decrease in sperm percentage and an increase in apoptotic cells after cell phone exposure (2 hours a day for 35 days) [30].
The number of apoptotic cells was evaluated across all groups in the present study. It was observed that the groups affected by 2100 MHz electromagnetic waves had a significant rise in apoptosis. This result was in line with Kesari et al. [30] findings, though our frequency used here (2100MHz) was different from Kesari et al. (2.45 GHz) [30].