The Effect Of Dexamethasone On The No-reflow Phenomenon After Restoration Of Coronary Blood Flow In Rabbits With Experimental Acute Myocardial Infarction

OBJECTIVE To observe the effect of dexmathasone on the no-reflow phenomenon in rabbits undergoing acute coronary artery occlusion -reperfusion.METHODS Rabbit's acute ischemia/reperfusion model was carried out by suturingthe left circumflex coronary artery for 60 mins and then removed the ligation to restore the blood supply for 60 mins.40 New Zealand white rabbits were divided randomly into 4 groups.Dexamethasone lmg/kg(group Ⅰ , n=10),5mg/kg(groupⅡ, n=10),5mg/kg (group Ⅲ, n=10)and 0.9% NaCl solution 5ml(control group n=10) were given intravenously 30mins before the occlusion of coronary artery. The no-reflow area (NRA) were determined by injection of thioflavin S into the auticle of left atrium at the end of reperfusion,and the Myocardial infarction Area(MIA) were determined by triphenyltetrazolium(TTC) staining .The extent of NR and infarction were expressed as percentage of LV area. i.e. NRA/LVA and MIA/LVA. The ST segament elevation in electrocardiogram (ECG) were measured at 60min after ligation and 60 min of reperfusion, The index of ST segament elevation( ∑ STI) and its rangeability(△%∑STI) was calculated.Serum level of CK were measured at 10min before ligation and 60 min of reperfusion. Serum level of TNF- α and IL-6 were measured at 60 min of reperfusion.RESULTS (1) NRA/LVA: At 60-min of reperfusion,The NRA/LVA of bothgroup Ⅱ and group Ⅲ are smaller significantly than either control group or group Ⅰ respectively(P<0.01).There is no significant difference in Control group and group Ⅰ , There is no significant difference in Group Ⅱ and group Ⅲ (2) MIA/LVA: At 60-min of reperfusion,The MIA/LVA of both groupⅡ and group Ⅲ are smaller significantly than either control group or group Ⅰ respectively (P<0.01) . There is no significant difference in Control group and group Ⅰ , There is no significant difference in Group Ⅱ and group Ⅲ (3) ∑ STI: At 60-min of ligation , ST segament elevated significantly.after 60 mins of reperfusion,The elevated ST segament decreased quickly. △ % ∑ STI (absolute value) of group Ⅰ , group Ⅱ and group Ⅲ are all larger than that of control group respectively. △ % ∑ STI (absolute value) of both groupⅡ and groupⅢ are larger than that of group Ⅰ respectively., There is no significant difference in group Ⅱ and groupⅢ (4) CK,TNF- α and IL-6:At 60-min of reperfusion,Both serum level of CK ingroup II and group III are significant lower than that of control group and group I respectively. (PO.01) , There is no significant difference in control group and group I(P>0.05), There is no significant difference in group II and groupIII (P>0.05);Serum level of TNF- a in group I ,group II and group III are all lower than that of control group respectively (P<0.01). Both serum level of TNF- a in group II and groupIII are lower than that in group I respectively (PO.01) , GroupIII are significant lower than Group II respectively. (P<0.01) . Serum level of IL-6 in group I , group II and group III are all lower than that in control group , Group II and groupIII are lower than group I respectively. (P<0.01) , There is no significant difference in GroupIII and Group II(P>0.05) .CONCLUSION A single dose of dexamethasone can decrease NR area andinfarct size, extenuate myocardial injury significantly in experimental acute myocardial ischemia/reperfusion, the effect of glucocorticosteroid correlates with its dose,higher-dose have a better effect at a certain range,The inhibition of TNF- a and IL-6 expression was probably involved in the mechanism of glucocorticosteroid.