| With the widely application of radiation source and rapidly developing of the electric power in our country, it has created a great deal public concern about health impact induced by low dose radiation and low frequency of electromagnetic fields. Many articles investigated the cumulative effect of exposures to low dose radiation and low frequency of electromagnetic fields in vitro and/or in vivo. A series of epidemiological studies showed controversial results.Since 1972, epidemiological studies at high background radiation area (HBRA) have been carried on. The conclusion about the relation between low dose radiation and cancer has been published at several articles. And a number of researchers have found increased risk of cancer among children who live close to power lines or among men whose jobs expose them to unusually high levels of EMFs.HSP70 are highly conserved molecular chaperones with physiological function which located in chromosome 1,5,6,9,11,14. They can be induced by heat stress, oxidative stress, ischemia-reperfusion, inflammation, and infected. HSP70 and the other proteins can built a stress-damage repair system by stress state.Objective:The present study aims to estimate the associations between the expression levels of heat shock protein 70(HSP70)and stress adaption on the exposed population from chronic low dose radiation and power frequency of electromagnetic fields. To find HSP70 whether is considered as the susceptible biomarker. The expression levels of the HSP70 in the peripheral blood and/or sputum of residents are determined in the exposed population.Methods:Fifty-three residents is the range from 50 to 59 years old in the HBRA and the CA were selected as exposed and control group, respectively. The levels on both mRNA and protein of the HSP70 in sera or sputum were determined by RT-PCT or Western blotting assay, respectively. Another study was conducted in the exposed population from 500kV electric substation and the nonexposed population from the executive staff. The number of the exposed population is 263 while the number of the nonexposed population is 252 as a control group.The age of both populations is in the range from 20 to 50 years old. The concentrations of the HSP70 in sera were determined by the ELISA assay.The contents of the questionnaire including general conditions, physical stress and psychological stress, for example age, education, income, medical exposure, dietary intake, smoke, drink.HSP70mRNA was detected with RT-PCR. The levels of HSP70 protein were detecte with western blot and ELISA, respectively.Statistical analysis was performed by SPSS13.0. A statistical level of P<0.05 was considered significant.Results:1 low dose radiation exposure population1.1 The average age of RA and HBRA is 54.3±3.8 and 53.4±3.4 respectively, the difference was not statistically significant (t=1.187,P=0.585) by t test. The difference of age percentage distribution was not statistically significant (χ2=2.034,P=0.154)byχ2 test. The difference of medical exposure, smoking, drinking, tea, mental stress and physical stress was not statistically significant(P>0.05),except for tea (P<0.05).1.2 The range of external radiation exposure on RA and HBRA population was 0.72-1.96mSv.a-1 and 2.20-4.84mSv.a-1 respectively, the average of effective dose from eternal exposure is 1.224mSv.a-1 and 3.480mSv.a-1,the difference was statistically significant (F=274.573,P=0.000) by analysis of variance.1.3 There was no statistically significant in concentrations of both HSP70 mRNA and HSP70 protein in the HBRA and RA by t test and covariance analysis.2 power frequency eletromagnetic field exposure population2.1 The average age of control group and exposurers is 30.88±6.102 and 31.95±6.62 respectively, the difference was not statistically significant (t=-1.902, P=0.580) by t test. The difference of age percentage distribution was not statistically significant (χ2=1.461,P=0.833)byχ2 test.The difference of sex percentage distribution was not statistically significant (χ2=0.021,P=0.885) by chi-square test. The difference of medical exposure, smoking, mental stress and physical stress was not statistically significant(P>0.05),except for tea and drinking(P<0.05).2.2 The intensity of electric field at workplace on control area and 500kV electric substation was 0.0066～0.1490 kV/m and 0.0009-14.0000kV/m respectively, the intensity of magnetic field is 0.03-0.33μT and 0.62-32.02μT.2.3 There was no statistically significant in concentrations of HSP70 protein by t test and covariance analysis.Conclusion:The results of the present study showed there was no significantly difference in the concentration of both the HSP70 mRNA and the HSP70 protein between the HBRA and the CA. The previous studies showed that there was no induction of HSP70 for low dose radiation for radiation could be one of the incentives. Some studies showed that the HSP70 was induced by the radiation in myeloid leukemia cell line. The result was opposite with epidemiology research, which indicated the health impact systems was complicated.In the other research about power frequency eletromagnetic fields, we also found no statistically significance of HSP70 expression on 500kV electric substation exposed workers and the control people. It was accord to christopher A's study that there was no induction of HSP70 by 6.3μELF EMFs in HL60 cells. There were many negative reports about ELF EMFs research.We suggested it was attributed by different experimental condition, and little epidemiology research support.The expression of HSP70 could be affected by confounding factors. Our research indicated that chronic exposured to low dose radiation or power frequency electromagnetic fields could not lead to induction of HSP70 expression. HSP70 expression could be associated with HSP70 gene polymorphism and confounding factors. More research should be launched to find the biomakers of low dose radiation or power frequency electromagnetic fields exposurers.Based on the. potential causes for the conflicting data from the reported suggestions and statements about low dose radiation or power frequency electromagnetic fields, more research should be continued to resolve the controversial data. |
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