| Background and Objectives: Percutaneous transluminal coronary angioplasty (PTC A) has already became the main way of treatmeat of the coronary heart disease. Intracoronary stent placement has helped to lower the coronary restenosis (RS) rate after PTCA significantly, but there are still some RS rate.Many researching results about the RS have been reported. But almost all prophylactic-therapeutic measures reported were not satisfied. The RS rate is still higher (about 15%-20%). This seriously affected the further development and long-term therapeutic effect of PTCA and stent implantation. Thus, it is imperative to find out some new prophylactic-therapeutic measures. Recently, some researchs show that endothelial cell has a close correlation with RS. The speed of endothelial regeneration and repair followed by coronary injury has important effects on the degree of RS.To accelerate reendothelialization may be the effective measure to prevent and cure the coronary RS. Meanwhile,the dysfunction of regenerated endothelium and reduced endothelial nitric-oxide synthase activity expression are also important factors leaded to RS. Researchs show that magnetic field have effect of promoting some kind of cells'sproliferation and tissue repair of injuries. It also can enhance most enzyme activity expression in cell. This study was designed to investigate the effect of low frequency electromagnetic field (LFEMF) of different intensity and time and static magnetic field (SMF) on DNA synthesis and cell cycle progression of human umbilical vein endothelial cell (HUVEC) as well as the expression of NOS in HUVEC and to discuss if LFEMF or SMF can be used in the prevention of the coronary artery RS after PTCA and stent implantation.Methods:(l) Human umbilical vein endothelial cells line (ECV304) were cultured in vitro with DMEM and 10 percent calf plasma. The HUVEC were cultured with LFEMF and SMF of different intensity and time respectively.(2) The numbers of HUVEC proliferation was monitored by 3H-TdR incorporation and the changes in cell cycle progression of synchronized HUVEC were examined by flow cytometric(FCM) analysis. (3)ABC immunohistochemistry technique and image analyzing method were used to evaluate the effect of the LFEMF and SMF on the expression of NOS in HUVEC.Results: (1) The HUVEC proliferation is significantly promoted by LFEMF at first and significantly inhibited by LFEMF with the time prolonged (P<0.05) . Cpm numbers of HUVEC proliferation of all the LFEMF groups are significantly different from that of control group (?<0.05), except 20 mT 30 min group, 40 mT 20 min Group. The cell cycle tested through FCM method show that the HUVEC proliferation is significantly promoted by LFEMF of appropriate intensity and time, cells of the S phase in the LFEMF group were higher than those of the control group, cells of the GI phase in the LFEMF group were lower than those of the control group, the proliferation index(PI) are increased markedly in the LFEMF group, but the HUVEC proliferation is significantly inhibited by LFEMF with the time prolonged (P<0.05) .(2) The expression of ecNOS in LFEMF group is more than the control group except 60mT 20min group and 60mT 30mingroup(P<0.05), There is no expression of iNOS in each group. (3) The cpm of SMF group is significantly higher than that of control (P<0.05) . The cells of the S phase in the SMF group are higher than those of the control group, cells of the GI phase in the SMF group are lower than those of the control group, the PI are increased markedly in the SMF group (P<0.05) .The expression of ecNOS in SMF group is more than the control group (P<0.01). There is no expression of iNOS in each group.Conclusion: (l)The HUVEC proliferation is significantly promoted by LFEMF of appropriate intensity and time. (2)LFEMF of appropriate intensity and time can enhance the expression of ecNOS in cultured HUVEC,but do not enhance the expression of iNOS in cultured HUVEC. (3) The HUVEC proliferation is significantly promoted by SMF of appropriate intensity...
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