| Objectives:To investigate the effect of cardioplegia with Na+ channel inhibitor tetrodotoxin(TTX) on expressions of intercalated disc proteins in isolated rat hearts.Methods:20 wistar rats were randomly divided into TTX group (experimental group) and STH-2 group(control group).Langendorff and Neely perfusion models were steadily established for 30 minutes,then the rat hearts(10 hearts in each group)were respectively arrested by TTX cardioplegia in TTX Group,and by St.Thomas-No.2 cardioplegia in STH-2 Group.These arrested hearts were preserved at 4℃for 60 minutes and underwent reperfusion for 60 minutes.Left ventricular myocardial samples were harvested for detection.Expressions of the intercalated disc proteins (Dsp,desmin, Cx43, N-cadherin,α-actin)were detected by immunohistochemistry (IH) and western blotting(WB).The arrest and recovery situation as well as hemodynamic parameters of the rat hearts (HR,CAF, LVESP,±dp/dt)were studied.Results: Desmosome proteins(Dsp and desmin) detected by IH in TTX group was better distributed than that in STH-2 group.The Dsp and desmin expressions detected by IH in TTX group were much higher than those in STH-2 group(0.0547±0.0057 vs 0.0451±0.0084 and 0.0513±0.0003 vs 0.0343±0.0003,P < 0.01). The Dsp and desmin expressions detected by WB in TTX group were much higher than those in STH-2 group(1.1773±0.0075 vs 0.7997±0.0080 and 1.1422±0.0362 vs 0.7648±0.0215,P<0.01).Gap juncton protein(Cx43) detected by IH in TTX group was better distributed than that in STH-2 group. The Cx43 expression detected by IH in TTX group was much higher than that in STH-2 group (0.0229±0.0014 vs 0.0166±0.0008,P<0.01). The Cx43 expression detected by WB in TTX group was much higher than that in STH-2 group (0.9829±0.0079 vs 0.5047±0.0067,P<0.01).Adherin junction proteins(N-cadherin andα-actin) detected by IH in TTX group was better distributed than that in STH-2 group. The N-cadherin andα-actin expressions detected by IH in TTX group were much higher than those in STH-2 group(0.0677±0.0003 vs 0.0243±0.0003 and 0.0738±0.0005 vs 0.0305±0.0002,P<0.01). Theα-actin expression detected by WB in TTX group was much higher than that in STH-2 group (1.0178±0.0158 vs 0.3828±0.0137,P<0.01).The arrest and recovery were remarkably better in TTX group (P<0.05)compared with STH-2 group. There were no differences in myocardial hemodynamic parameters between the two groups before MIRI,but the recovery of myocardial hemodynamic parameters during reperfusoin in TTX group was better than that in STH-2 group (P<0.05).Conclusion:Compared with STH-2 cardioplegia ,the expressions of intercalated disc proteins(Dsp,desmin,Cx43,N-cadherin,α-actin) were much higher in TTX cardioplegia.It was suggested that the damages to intercalated disc proteins of isolated rat hearts arrested by TTX cardioplegia were less severe than those in STH-2;structure of intercalated disc and heart function were better protected with TTX cardioplegia.TTX cardioplegia played a better myocardial protection in isolated rat hearts than STH-2.
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