| In spite of investigations into advanced theraputic and interventional approaches over the last 20 years,ischemic heart disease remains a major worldwide cause of death and disability .It is therefore important to develop new effective therapeutic approaches to treat myocardial ischemia.A hallmark of myocardial ischemia is an imbalance between oxygen supply and demand,resulting in profound changes in metabolism,which contributes to arrhythmias and a decrease in cardiac efficiency.A novel approach to the treatment of ischemic heart disease,which was introduced in the 21th Europe Society of Cardilology, is to improve the efficiency of oxygen utilization by the heart muscle.Alterations in myocardial lipid metabolism during myocardial ischemia can have profound effects on the physiological status of the heart through changes in membrane fluidity, membrane integrity and the activation of signaling cascades.H-FABP is a low molecular weight(15KD) cytoplasmic protein and that is abundant in the cytoplasm of myocardial cells. It is most abundant in adult heart ,and also present in an read skeletal(slow twitch)muscle, aorta, smooth muscle cells, et al. The proposed roles of H-FABP include:(i) enhancing the uptake of fatty acids into cells and facilitating their transport to intracellular organells,(ii) protecting enaymes and membranes from the effects of free fatty acids and their acyl-CoA derivatives, (iii) maintaining a large intracellular pool of fatty acids for rapid mobilization,and targeting fatty acids to specific metabolic pathways.H-FABP indisputally plays a pivotal role in muscular fatty acid utilization, and prevent the myocyte from excess triglyceride accumulation which inducing lipotoxicity.It has been demonstrated that the expression of H-FABP can be induced by an elevated fatty acid-dependent metabolism.But the study of H-FABP mRNA and protein expression in early acute myocardial ischemia has not been overally discussed.Objective: The present study was designed to observe the changes of H-FABP expreesion in rats'myocardial ischaemia tissues, and demonstrate the probable mechanisms involved at different levels included in vivo.Methods: 1,The rat model of acute myocardial ischemia was induced by ligating the anterior branch of the left coronary artery in accordance with the method of Selye. 80 Sprague-Dawley (SD) male rats, weighting 250-350g, were randomly distributed into Sham-operated groups and five study groups. The left coronary artery of rats in the five study groups was ligated for 1h, 2h, 4h, 6h ,12h (group A1, A2, A3, A4, A5 )respectively. The expreesion level of H-FABP in ischemia myocardia were detected with RT-PCR and Western Blot . The relative expression quantity of each band was represented with the ratio of band peak area integrated optical density (IOD) of H-FABP to that ofβ-actin or GAPDH . The concentration of free fatty acid in serum was measured with once extract colorimetric method.Result The experimental results were as follows:(1) establishment of acute myocardial ischemia model After ligating the anterior branch of the left coronary artery,the greater than 0.01mv elevation of ST-T section in lead II or striking widen of QRS wave in lead V1-V3 had been lasted for more than 30 minutes.With Evans and TTC dye in sucession respectively,the non-ischemia zone or normal myocardism was dyed to be blueness;ischemia zone or danger but survival myocardism ,to be brick erythrine;infarction zone or necrosis myocardism ,to be grey white.(2) the result with myocardial HE staining In the Study group A1,A2,A3 ischemia group; none of them had macroscopic or microscopic evidence of myocardial infarction, only appear- ing myocyte swelling with various extent. While in the ischemic 6h/12h group (group A4, A5) some cardiac muscle fibers arranged disorder and shew up fragmentation/vague dividing lines,forming so-called"Contraction bands",even some myocyto zeone offered"coagulability necrosis"around a sprinkle/bulk neutrophilic leukocyte and akaryocyte within interstitial tissue. (3) H-FABP protein assay The integrated optical density(IOD) of H-FABP/GAPDH in Sham group and A1,A2,A3,A4,A5groups was 58.62±12.28 %,50.74±9.37 %,42.42±12.63 %,41.38±12.89 %,34.25±8.42 %,and 40.41±3.20 % respectively; contrasted to Sham-operated rats , the means of every study groups was decreased within 2,4,6,12 hours ischemia significantly(P<0.05). especially 6 hours ischemia group,H-FABP protein tended to be lower 41%(P<0.01)of those of control group.(4) H-FABP mRNA assay the IOD values of Sham group and A1,A2,A3,A4,A5groups were 91.33±3.58 %,77.29±12.76 %,70.70±12.82 %,64.80±4.19 %,64.43±17.23 % and 68.89±9.28 % respectively;Compared with Sham-operated rats, the means of every study groups was decreased gradually with the prolonged ischemia time, especially 2,4,6,12 hours group significantly(P < 0.05).Within 4,6 hours ischemia groups,H-FABP mRNA tended to be lower 29%,30%(P<0.01)of those of control group.(5)Serum FFA contents The serum FFA contents of Sham group and A1,A2,A3,A4,A5groups were (181.01±94.84)umol/l,(263.43±100.89)umol/l,(379.95±247.43)umol/l,( 492.23±369.25 ) umol/l ,( 224.71±168.89 ) umol/l ,( 186.23±161.30 ) umol/l respectively. Compared to Sham-operated rats, elevated FFA contents were observed only in rats underwent 1, 2 and 4 hours ischemia;especially 4h ischemia increased FFA level significantly(P=0.007). In 2 and 4 hours ischemia group ,the FFA values was 2.01 times and 2.72 times than that of Sham group. While 6 and 12 hours ischemia group were not changed significantly compared to that of sham group (P>0.05).Conclusion: The obviously downregulation of H-FABP mRNA and protein in ischemia survival myocardium indicated that ischemical survival myocytes descreased the intake and transport of fatty acids graudally along with ischemic intervel enlongation, which might paly a role in acute myocardial injury and affect the prognostic of acute myocardial infarction.
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