Effect Of Nitroglycerin Preconditioning On The Expression Of Caveolin-3 In The Cardiac Muscular Tissue

Objective To investigate the effects of different dosage of nitroglycerin on the hemodynamics of the rats and the effects on the myocardial ischemia-reperfusion injury and to investigate the expression level of caveolin-3 in the cardiac muscular tissue.MethodsExperiment 1:Thirty-two male SD rats were randomly assigned to 4 different groups: Ischemia-reperfusion(I/R) group﹑ 2μg/(kg·min) nitroglycerin preconditioning(PC₁) group﹑4μg/(kg·min) nitroglycerin preconditioning(PC₂) group and 6μg/(kg·min) nitroglycerin preconditioning(PC₃) group. We used the micro intravenous injection pump to continuous pump different dosage of nitroglycerin into the rats through the caudal vein in one hour and to continuous monitor the mean artery pressure (MAP) of the rats through the carotid arteries. The isolated rats hearts were perfused on a Langendorff apparatus passively with 37℃Kerbs-Henseleit buffer(KHB) saturated with 95%O2-5%CO₂. We made the isolated rats hearts to undergo 30 min ischemia and then followed by 90 min reperfusion. We measured the heart rate(HR),left ventricular systolic pressure(LVSP),±dp/dt_max and coronary flow (CF) before ischemia and at 5﹑15﹑30 min after the reperfusion. We also measured the cardiac troponin I(cTnI) and the nitric oxide(NO) concentration in the left ventricular muscles homogenate after the reperfusion.Experiment 2:Twenty-four rats were randomly assigned to 3 different groups: Ischemia-reperfusion (I/R) group﹑ nitroglycerin preconditioning (PC) group and M-β-CD treatment (M) group. The isolated rats hearts were perfused on a Langendorff apparatus passively with 37℃KH buffer saturated with 95%O₂-5%CO₂. The I/R group were made to undergo 30 min ischemia and then followed by 90 min reperfusion. The PC group were continuous pumped small dosage of nitroglycerin [2μg/(kg·min), total dosage 120μg/kg] into the rats through the caudal vein in one hour. M group were perfused passively with K-H buffer containing 0.2 mmol/L M-β-CD. We measured the LVSP,±dp/dt_max and CF before ischemia and at 30 min after the reperfusion. We measured the cTnI concentration in the left ventricular muscles homogenate through ELISA and the NO concentration in the left ventricular muscles homogenate through the chemical method after the reperfusion, we also mesured the apoptosis of the cardiac myocytes through TUNEL, and measured the expression level of caveolin-3 in the different cardiac myocytes through immunohistochemisty and PCR. Results(1) PC₁ group had no significant effects on the MAP, but PC₃ group significantly decrease the MAP. Campared with the I/R group, the PC₁ group significantly improved the HR﹑LVSP﹑±dp/dt_max and the coronary flow, reduced the cTnI and improved the NO concentration in the left ventricular muscles homogenate( P< 0.05); Campared with the PC₃ group, the PC₂ group significantly improved the HR﹑ LVSP﹑±dp/dt_max and the coronary flow( P< 0.05), but had no significant difference campared with the I/R group(P>0.05); Campared with the I/R group, the PC₁ group decreased the cTnI and increased the NO concentration in the left ventricular muscles homogenate significantly( P< 0.05); the PC₂ group significantly increased the cTnI and NO concentration in the left ventricular muscles homogenate;and the PC₃ group increased the cTnI and NO in the left ventricular muscles homogenate extremely significantly( P< 0.05).(2) Compared with the I/R group, the LVSP﹑±dp/dtmax and the NO concentration of the PC group were significant highe(rP<0.05) and while the the cTnI﹑apoptosis of the cardiac myocytes were significant lower( P<0.05 ) , both immunohistochemisty and PCR showed that the expression level of caveolin-3 were significant higher in the PC group; campared with the I/R group, the M group had no significant difference.Conclusion The effects of NO donor on the ischemia-reperfusion myocardial cell has relevance to the dosage: Continuous pumping 2 μg/(kg·min) of nitroglycerin in one hour has no significant influence on the hemodynamics but can increase the NO concentrate in the ischemia cardiac muscle and alleviate the cardiac myocytes injury significantly,6μg/(kg·min) of nitroglycerin can extremely increase the NO concentrate in the ischemia cardiac muscle and then aggravate the cardiac myocytes injury significantly. Continuous pumping small dosage of nitroglycerin in one hour afford the myocardial protection may through increasing the expression level of caveolin-3 in the myocardial cell.