The Protecting Effect Of L-glutamine On The Injury Of Infrasound To Rats Brains

Infrasound(infrasound, IS) is a kind of sound wave generated by vibration, widespreading in nature, industrial and agricultural production and transportation environment. It becomes an important part of public and industrial noise. Long-term of high-intensity sound (noise) exposure can lead to damage on multi-body system, multi-organ structure and function, particularly central nervous system (CNS). Long-term infrasound environment is not only physically and psychologically harmful to people, but can also further lead to decreased work efficiency, and even security. With the social development in recent years, infrasound becomes more prominent, which calls for more effective protective measures. Because of the small attenuation of infrasound, long-distance transmission and good penetrability, it is difficult to protect from infrasound. Now the main protective measures include physical and medical protection. There is little progess in the new shielding materials to isolate from infrasound. Medical research shows that: the use of anti-free radicals drugs, the composite antioxidants can reduce the harmful effects of infrasound on the body. Anti-oxidant may be an effective method to protect from infrasound.L-glutamine (L-Gln), one of the most abundant free amino acids and the body's essential amino acids, takes the following physiological roles: synthesis of biological macromolecules; antioxidant; transfer function; the maintenance of immune function; the maintenance of the acid-base balance in the body; adjusting the balance of blood glucose. It works as an antioxidant through the following mechanisms: 1. Oxidation as a source of energy, it is a kind of main energy-providing material for mitochondrial to produce adenosine triphosphate (ATP); 2. It takes part in the regulation of enzymes involved in apoptosis and the balance of intracellular redox; 3. As the precursor substances of glutathione peptide (GSH), it can reduce the oxidative stress; 4. It can induce the expression of heat shock protein (HSP), maintain the cells metabolism and structural integrity, avoid apoptosis and necrosis; inhibit nitric oxide (NO) synthesis to reduce ischemic injury on cardiovascular system.L-Gln is a nutritional substance which exists in the body, and is safe without toxic side-effects. With its wide range of physiological functions, it has been effectively used in-depth in clinical, nutrition and sports medicine etc. Its multiple anti-oxidation effectiom provides the theoretical basis for protection from infrasound.S-100βprotein presents specifically in glial cells of CNS. It can not pass the blood-brain barrier (BBB) under normal circumstances with low content in serum. After brain damage, S-100βprotein is released from damaged glial cells into cerebrospinal fluid. Through the destructed BBB, it is then released into serum, so that the serum S-100βprotein level is increased rapidly. Therefore, S-100βprotein is highly sensitive to and specific for the brain damage, and its concentration in serum reflects the extent of brain injury, by which it has become by far the most suitable protein marker to reflect the degree and prognosis of brain injury. In general, the higher S-100βprotein serum level is, the more serious brain damage is, and the worse the prognosis is.Free radicals and free radicals scavenger have important value for guiding the clinical intervention measures, establising the best therapeutic time window as well as determing the prognosis. The existence of free radicals scavenging system is very important to reduce the brain damage, block the excitotoxicity and prevent the damage caused by the cascade. Therefore, the superoxide dismutase (SOD) activity and malondialdehyde (MDA) content in brain tissue are important indicators to evaluate brain damage and drug effect.In accordance with the requirements of the experiment, the rats were given L-Gln and/or infrasound treatment. By comparing the learning performance of rats in each group, concentration of S-100βprotein in peripheral serum, the SOD activity and MDA content in brain tissue and apoptosis and necrosis ratio of hippocampal cells to test whether L-Gln has any protective effect on infrasound-induced brain injury. Experiments were as follows:1. Animal grouping, model preparation and specimen collectionUsing Y-electric maze to select 64 rats with similar learning ability. Rats were randomly divided into 4 groups: normal control group, infrasound group (16Hz/130dB), infrasound + drug group (16Hz/130dB infrasound + L-Gln), drug→infrasound group (L-Gln for 7 days, and then exposed 16Hz/130dB infrasound). No special treatment was performed on the normal control group, and the remained 3 groups were performed to L-Gln and/or infrasound treatment. 7 days later, the latency of the rats to find platform (Morris water maze test) was tested as the indicator of learning ability; the serum was separated and frozen for the detection of serum S-100βprotein concentration; the brain was removed and reserved for detection of the SOD activity and MDA content in the brain tissue; hippocampus was isolated and the cell suspension was collected to detect the apoptosis and necrosis ratio of hippocampal cells.2. The protective effect of L-Gln on infrasound-induced rats learning disabilities.Rats were exposed to 16Hz/130dB infrasound environment 2h/d for 7 days. The infrasound group rats showed significant longer latency (P<0.01) to find the platform than the normal control group rats; the drug-treatment group rats, to give L-Gln whether in advance or at the same time, the rats exhibited significantly shorter (P<0.05) latency to find the platform; compaired with the L-Gln in advance treatment group rats, the L-Gln simultaneous treatment group rats have shortened incubation period although without significant difference (P>0.05). Conclusion: L-Gln can improve the learning disabilities caused by infrasound on rats brain injury. No statistical significance was found between the L-Gln treatment in advance and at the same time.3. The effects of L-glutamine on S-100βprotein concentration in rats serum after infrasonic brains damage The concentration of S-100βprotein in the peripheral blood is extremely low in the normal control group rats. Compaired with the normal control group rats, the S-100βprotein concentration in the other three group rats was significantly increased (P<0.01). Compaired with the infrasound group rats, S-100βprotein concentration in the infrasound + drug group and drug→infrasound group rats decreased significantly (P<0.05). Compaired with the infrasound + drug group rats, S-100βprotein concentration in the drug→infrasound group rats increased significantly (P<0.05). Conclusion: Infrasound (16Hz/130dB, 2h/d, 7d) may increase the serum S-100βprotein concentration significantly, suggesting that infrasound can damage not only brain tissue, but also blood-brain barrier (BBB). L-Gln can partly reduce the extent of brain injury. Administration in advance of drug can reduce injury, but the protective effect was weaker than the effect of administration at the same time.4. The effect of L-Gln on the SOD activity and MDA content of infrasound-injuried rats brainsCompared with the normal control group rats, the SOD activity of the infrasound group rats increased (P<0.05); that of the infrasound+drug group and drug→infrasound group rats increased more significantly (P<0.01). Compaired with the infrasound group rats, the SOD activity of the infrasound + drug group rats increased significantly (P<0.01); that of the drug→infrasound group rats also increased (P<0.05). And compaired with the infrasound+drug group rats, the drug→infrasound group rats showed lower SOD activity (P<0.05). Conclusion: infrasound (16Hz/130dB, 2h/d, 7d) can increase the SOD activity in rats brains, evoke the stress reaction of antioxidant enzyme system to protect from the free radicals damage on the brain; L-Gln can improve the capacity of the system of antioxidant enzymes, thereby enhance the function against the free radical damage. Administration of L-Gln in advance makes a smaller effect than that of administration at the same time. Compared with the normal control group rats, the MDA content increased in infrasound group (P<0.01), the infrasound + drug group (P<0.05) and drug→infrasound group rats (P<0.01). Compaired with the infrasound group rats, the MDA content in the infrasound + drug group rats increased (P<0.01), the drug→infrasound group rats increased (P<0.05). It showed a decreased MDA content in the frasound + drug group rats than in the drug→infrasound group rats (P<0.05). Conclusion: infrasound (16Hz/130dB, 2h/d, 7d) can lead to the increased content of MDA in rats brain and the level of lipid peroxidation, suggesting the damage of the brain tissue by infrasound; L-Gln can partly reduce the extent of infrasound-induced brain injury. Administration drug in advance can reduce injury, but the protective effect was weaker than the effect of administration at the same time.5. The effect of L-Gln on the apoptosis and necrosis ratio of hippocampal cells after infrasound exposure.Compared with the normal control group rats, apoptosis and necrosis ratio of hippocampal cells in the infrasound group rats increased significantly (P<0.01). Compaired with the infrasound group rats, the ratio of the apoptosis and necrosis of hippocampal cells of the infrasound + drug group and drug→infrasound group rats decreased significantly (P<0.01). Compaired with the drug→infrasound group rats,it showed a lower ratio of hippocampal cells apoptosis and necrosis in the infrasound+drug group , which had no significant difference between them (P>0.05). Conclusion: infrasound (16Hz/130dB, 2h/d, 7d) administration can induce apoptosis and death and lead to cellullar damage in hippocampus; L-Gln can partly prevent and protect from the infrasound-induced injury on the rat hippocampus.In this experiments, by using L-Gln and/or infrasound (16Hz/130dB, 2h/d, 7d) to deal with the rats, we compaired the learning ability, concentrations of S-100βprotein in serum, the SOD activity and MDA content in brain tissue and hippocampal cells apoptosis and necrosis ratio. The results suggest that L-Gln can partly prevent and treat the infrasound-induced brain injury which provided a reliable practical basis for the infrasound protection.