Effects And Its Related Mechanism Of EMP Exposure On The Reproductive Endocrine Function Of Male Rats

Electromagnetic Pulse (EMP) is a high energy electromagnetic wave with an extremely fast rising time and a broad bandwidth. Because it is widely used in industry, medicine and other fields, its biological effects has become a focus of academic research. Faced with the increasing electromagnetic pollution, it is the academic task to reveal its hazards to human health and the potential mechanism.Many studies indicate that electromagnetic radiation can cause reproductive endocrine toxicity and genetic toxicity. It has also been reported that parental exposure to electromagnetic radiation can cause long-term genetic toxicity to the reproductive health of male offsprings, but the relevant mechanism is not clear. Hypothalamic-pituitary-gonadal axis is the control core of animal reproductive system's development and function. The inhibitory neurotransmitter GABA is one of the most important regulators, primarily through the hypothalamus GABA_A receptor, regulating GnRH secretion, promoting the secretion of pituitary hormones, ultimately achieving the regulation of animal reproductive endocrine function. Therefore, the hypothalamic GABA_A receptor expression plays an important role in the regulation of reproductive endocrine function. In our previous study we found that EMP caused the increase of GABA in the hypothalamus in the male offspring. Based on the above theory foundation and research results, in our study, we used radioimmunoassay, immunohistochemistry and Real-time PCR to investigate the effect and its mechanism of EMP on reproductive endocrine function in SD male rats and the male offspring from morphology, hormones and neurotransmitter aspects. AIMSTo investigate effects and its mechanism of EMP on reproductive endocrine function in male rats and the male offspring.METHODS 1. Adult and young male SD rats were respectively sham or whole-body exposed to EMP at 200 kV/m for 400 pulses. The levels of GnRH, FSH, LH and T in serum were detected by radioimmunoassay. The expression of GABA_A receptor protein was assessed by Western blot.2. Parental male rats were exposured to EMP at 200 kV/m for 0, 100 or 400 pulses before mating:(1) The structural changes of pituitary and testis of the male offspring were observed by optical and electron microscope.(2) The levels of hormones in serum of the male offspring were detected by radioimmunoassay, the sperm acrosin activities were measured by gelatin lysis test,the sperm numbers, deformities and the reproductive behaviors were observed.(3) The expression of GABA_A receptor was assessed by Western blot, immunohistochemistry and Real-time PCR and hypothalamic GABA content of the male offspring was detected by HPLC.RESULTS1. The effects of EMP on hormones in serum of rats at different age: it was found that the serum levels of T were decreased significantly at 0.5 h and 12 h after exposure(P<0.05) and the levels of GnRH of adult male rats were increased significantly at 6 h and 48 h after EMP exposure(P<0.05). As to the yong male rats, the levels of T were decreased significantly at 0.5 h and 3 h after exposure(P<0.05); the serum levels of GnRH fluctuated after EMP exposure, increased significantly at 12 h after exposure(P<0.05). But the levels of FSH and LH in serum did not change obviously after EMP exposure.2. The effects of EMP on hypothalamic GABA_A receptor: compared to the control group, the results of Western blot showed that the expression of hypothalamic GABA_A receptor of the adult male rats increased significantly at 0.5 h after EMP exposure(P<0.05) and lasted to 6 h after EMP exposure(P<0.05), then began to recover, however it increased significantly again at 48 h after exposure(P<0.05). The GABA_A receptor expression of the young male rats were increased significantly at 3 h and 12 h(P<0.05), then began to recover and finally recovered to control level at 48 h after EMP exposure.3. The effects of parental exposure on the structure of pituitary and testis of male offspring: the histological structure of pituitary gland and testis did not change obviously under optical microscope in radiation group. Under electron microscope we found the slightly swelled mitochondria and dilatated endocytoplasmic reticulum in pituitary. Mainly ultrastructure changes of testis were dilatation of endocytoplasmic reticulum, swell of mitochondria and vacuolation.4. The effects of parental exposure on the serum hoemones and sperms of male offspring: we found that the T level and sperm numbers decreased significantly (P<0.05), the sperm acrosin activities were decreased significantly in male offspring of the radiation group. It did not show significant changes in the structure of pituitary and testis, sperm deformity frequency and reproductive behaviors.5. The effects of parental exposure on the GABA and GABA_A receptor: compared to the control group, the mRNA expression were increased in 100 and 400 pulses group, respectively 1.12 and 2.04 times of the control group. The content of GABA and the expression of hypothalamic GABA_A receptor protein increased in radiation group (P<0.05). We found that in the arcuate nucleus the numbers of the GABA_A receptor neurons and the IOD values were both increased significantly in the EMP group (P<0.05); in the paraventricular nucleus the number of GABA_A receptor positive neurons was significantly increased in 100 pulses group, the IOD value was increased significantly in 400 pulses group(P<0.05).CONCLUSIONS1. EMP of 200 kV/m, 400 pulses caused the alteration of serum hormones GnRH and T and the fluctuation of GABA_A receptor expression in rats at different age.2. Parental male rats exposure to EMP of 200 kV/m, 100 or 400 pulses induced the decrease of T, the decrease of sperm quantity and quality and the increase of GABA and GABA_A receptor in male offspring. 3. In this experiment condition EMP had a certain degree influence on the reproductive endocrine function of male rats and male offspring, the hypothalamic GABA_A receptor may be involved in the reproductive toxicity of male rats and the male offspring. However, the mechanism should be investigated specificly.