Mechanism Of EMP And X-ray Irradiation On The Increasing Of Myocardial Intercalated Discs Gap In Rats

Our life and radiation is getting closer and closer along with the application ofcommunication equipment, networking and medical equipment in life. But radiation caninduce some bad effects when it brings the convenience to us. So, more and moreresearches focus on it. Previous studies have shown that radiation can induce the changesof ECG(electrocardiogram) and blood pressure, and these changes were related withmyocardial intercalated discs （ID）, but the mechanism is not clear. In our study, theresearch objection includes SD rats and H9c2myocardial cell line. The experimentmethod includes electron microscopy, western blot, real time-PCR, MTT and so on. Wetry to find the effects of EMP and X-ray irradiation on the IDs and the gap junction proteinCx43. And we try to explore the probable molecular mechanisms of the biological effects. Objective:Study the effect of EMP and X-ray irradiation on the IDs and the gap junction protein inrats. And explore the mechanism of the biological effects.Methods:The SD rats were exposed to EMP and X-ray separately. EMP exposure parametersare as follow: field strength of200kV/m, cutting-edge of10ns, pulse width of7-8ns,pulse rimes of200times and pulse interval of7s. The radiation dose of X-ray is20Gy.Then the rats were sacrificed at0h,1h,3h,6h,12h and24h after EMP irradiation and at1h,3h,6h,12h and24h after X-ray irradiation, and the left ventricles were surgicallyexcised to prepare for the next experiments.1. The morphological changes of myocardium and IDs were observed by electronmicroscope using the method of lanthanum nitrate tracer.2. The protein expression levels of gap protein Cx43, p-Cx43, Cx40and Cx45weredetected by Western Blot method.3. The mRNA expression levels of Cx43, Cx40, Cx45and miR-1were detected by Realtime-PCR.4. H9c2（2-1）cells were exposed to X-ray of20Gy (the optimal radiation dose), andthen cells were harvested at1h,3h,6h,12h and24h after exposure. The protein expressionlevels of gap protein Cx43, p38, p-p38, ERK and p-ERK (MAPK pathway) were detectedby Western Blot. The mRNA expression levels of Cx43and miR-1were detected by realtime-PCR.Result:1.After EMP and X-ray exposure，myocardial cells of rats were damaged. ID gapwidened and the damage changed heaven after exposure, but these damages could berecovery automatically.2. After EMP and X-ray exposure, the protein expression levels of Cx43and p-Cx43increased. But there were not obvious changes of protein expression levels of Cx40andCx45.3. After EMP and X-ray exposure, the mRNA expression level of Cx43increased. But there were not obvious changes of mRNA expression level of Cx40and Cx45. The mRNAexpression level of miRNA came down.4. After20Gy of X-ray exposure, the protein expression levels of Cx43, p-Cx43andthe MAPK pathway related protein p38, p-p38, ERK and p-ERK in H9c2（2-1）cellsdecreased. The mRNA expression levels of Cx43in H9c2（2-1）cells increased and miR-1decreased.Conclusion:Both of EMP and X-ray can induce the follow changes.1. They can increase the gap ofIDs and damage the myocardial cells.2. They can induce the increasing of Cx43andp-Cx43and the decreasing of miR-1in mRNA levels.3. The mechanism of EMP andX-ray on the IDs probably were related to the Cx43and miR-1in mRNA and proteinlevels.