| Objective:The animal model of local heart irradiation was prepared by using X-rays, study the possibly molecular mechanism of myocardial apoptosis in early induced by local heart irradiation with X-rays. methods:Forty-eight male Sprague-Dawley(SD) rats were divided randomly into sham- irradiated control group(n=7) and local heart irradiation group(n=42). The rats of local heart irradiation group received a single X-ray dose of 20 Gy irradiation, and then the local heart irradiation group were divided into 12 h, 24 h, 2d, 4d, 1w, 2w subgroup,the rats were kill and the left ventricle were isolated at 12 h, 24 h, 2days, 4days, 1week, 2weeks after irradiation, the samples were fixed and make the paraffin sections to detect apoptosis of myocardial cells by TUNNEL; The experimental technique of real-time PC R and western blotting were used to detect the expression of mRNA and protein of BC L-2 associated X protein(Bax) and the protein of C ytochrome C(Cyt-C) in myocardium and the levels of Cyt-C from mitochondria in 1w and 2w subgroup as well as the Bax and truncated-BH3 interacting domain death agonist(t-Bid) from mitochondria in 12 h, 24 h, 2d, 4d, 1w subgroup. Results:1. generally: compared with sham- irradiated group, the weight of model rats in 1week after irradiation decreased significantly(P<0.05), in addition, there are some phenomenons of activity decreased and movement slow on the rats.2. the apoptotic detection: compared with sham- irradiated group, the myocardial cells appeared an significant apoptosis at time point from 12 h to 2 weeks after irradiation, and the most obvious apex of apoptosis at the 24 h.3. the real-time PCR results: the mRNA expression of Bax were significantly increased at time point in 1 week and 2weeks after irradiation, and compare with the 2w group after irradiation, the expressio n of mRNA was more significant in 1w group.4. the western blotting results: compared with sham- irradiated group, ○1 the expression of Bax and C yt-C increase in the 1w subgroup and 2w subgroup(P<0.05), while the expression of Cyt-C from mitochondria reduce significantly(P<0.05); ○2 the expression of Bax from mitochondria membrane increase at 12 h, 24 h, 2days and 4days after irradiation; ○3 the expression of t-Bid from mitochondria increased at 24 h, 2days, 4days after irradiation(P<0.05). Conclusion:1. an apoptosis of myocardial cells has occurred in the early-stage of RIHD.2. the possible mechanism of apoptosis in the early-stage of RIHD is the Pro-apoptotic protein Bax activated and translocated to mitochondria, which induced release of C yt-C when integrated with mitochondrial outer membrane.3. Bax may be associated with the mitochondrial membrane integration to form a specific channel with the help of t-Bid protein, which mediates the release of C yt-C. |
