| Myocardium protection is a critical technique during cardiac surgery . At present the usual method to be adopted for myocardial preservation is perfusing ST Thomas cardiopiegic solution which inevitably causes myocardial ischemia reperfusion injury ( MIRI) and low cardiac output syndromes and arrhythmia. Many cardioprotective measures have been suggested, but none of them are perfect. Epidemiological study discover that estradiol may decrease incidence rates of coronary heart disease. Animal experiments confirm that estradiol relieve MIRI. It is not proved yet whether 17β - estradiol - enriched cardiopiegic solution can protect isolated rat hearts against MIRI. To study the effects of 17 - estradiol - enriched cardiopiegic solution on MIRI and to investigate the cardioprotective mechanism in isolated mouse hearts on a Langendorff apparatus, coronory flow(CF) ,creatin phosphokinase (CPK) ,lactec dehydrogenase ( LDH) , malonaldehyde ( MDA ) , su-peroxide dismutase ( SOD ) , nitric oxide ( NO ) , nitricoxide syn-thase(NOS), inducible NOS(iNOS) and endothelial NOS(eNOS) are detected.MATERIALS AND METHODS1. Isolated Mouse Heart Preparation: Female Wistar rats weighing 230g to 260g were subjected to surgical bilateral ovariectomy. Two weeks after surgery the animals were used in the experiment in which MIRI responses to 17β - estradiol. Ovariectomy does not cause any loss in estrogen receptor. Mice were anesthetized with an injection of urethane(10 mg/kg IP) , and heparin (500 U/kg) was administered at the same time. Subsequently the heart was excised after thoracoto-my and placed into cold perfusion buffer. The aorta was cannulated, and the heart was perfused in a recirculating mode by means of the Langendorff technique at constant coronary pressure of 80mmHg with Krebs - Henseleit bicarbonate buffer (KHB) containing in(mmol/L) Nad 118, KC1 4. 6, MgS04 1. 2, NaHC03 24. 9, CaCl2 2. 5, KH2PO4 1.2, Glucose 10, and EDTA 0. 5, equilibrated with 95% 02, 5% CO2(PH 7.4, PO2 450 - 500mmHg,37℃). An isolated rat working heart model was established. Three phases protocal were performed : ( 1) minute preperfusion; ( 2 ) minute global ischemia; ( 3 ) 30 -minute or 60 - minute reperfusion. Afterl5 - minute preperfusion, cardiopiegic solution was perfused through aorta for 5min to stop beating and the hearts were undergone 30 - minute cardial schemia. Because of its high lipophility, estradiol was dissolved in dimethyl sulfox-ide ( DMSO) , 5umol17 - estradiol was first dissolved in 1ml DMSO, thislml stock solution was then added into 1000ml of ST Thomas cardiopiegic solution, which is called estradiol cardiopiegic solution.2. Perfused hearts were divided into three groups. GroupIR: Hearts are perfused with ST Thomas cardiopiegic solution, reperfusionfor 30min or 60min. GroupD: ST Thomas cardiopiegic solution containing 0. 1% DMSO ,reperfusion for 30min or 60min. GroupE; Hearts are perfused with estradiol cardiopiegic solution, reperfusion for 30min or 60min.3. The effluent was collected before ischemia and during reperfusion and stored at -20℃ for subsequent measurement of CPK, LDH and NO. Myocardial MDA, SOD, NOS, iNOS and eNOS are detected at the 30th minute of reperfusion or 60th minute of reperfusion.RESULTAfter 30 - minute or 60 - minute reperfusion, 17(3 - estradiol cardiopiegic solution apparently incrases CF( P < 0. 05, P < 0. 01) and NO( P <0. 01) ;decreases CPK and LDH in the coronary effluent; enhances cardiac myocyte SOD activity (P <0. 05,P <0. 01) ; reduce myocardial MDA( P < 0. 05 , P < 0. 01) ; reinforce myocardial cell iNOS activity(P < 0. 01) and NOS activity ( P < 0. 01) , but, eNOS activity obviously unchanging (P >0. 05) ; enhances the expression of cardiac muscle cell iNOS and iNOSmRNA( P <0. 05) ,it is more apparent that iNOS activity and the expression of cardiac muscle cell iNOS and iN-OSmRNA for 60 - minute reperfusion than 30 - minute reperfusion ( P <0.05) ,but the expression of cardiac muscle cell eNOS and eNOS mRNA is not obvious difference (P >0. 05) ; Ab...
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