Objective  To investigate the effects of pretreatment of nitroglycerin at a small dosage [2 μg/(kg·min)

]

on the hemodynamics of the rats with heart ischemia-reperfusion injury

and explore the mechanism of nitroglycerin preconditioning for myocardial protection on the rats.    Methods  Twenty-four rats were

completely randomly assigned to 3 different groups

ischemia-reperfusion (I/R) group

nitroglycerin preconditioning (PC) group and M-β-CD treatment (M) group. The isolated hearts were passively perfused on a Langendorff apparatus with 37 ℃ Kerbs-Henseleit buffer (KHB) saturated with mixture gas

which containing 95%O

2

-5%CO

2.

The I/R group was undergone 30 min ischemia and then 90 min reperfusion. The PC group was continuous pumping small dosage of nitroglycerin in 1 h before the hearts underwent the ischemia. The M group was passively perfused with K-H buffer containing 0.2 mmol/L M-β-CD. ELISA was used to measure the changes of left ventricle function and the cardiac troponin I (cTnI)

and nitrate reductase method was used to measure the nitric oxide concentration in the left ventricular muscles homogenate. The apoptosis of the cardiac myocytes was tested with TUNEL

and the expression of Caveolin-3 in the different cardiac myocytes was determined with immunohistochemisty and PCR.   Results  Compared with the I/R group

the LVSP

+dp/dt

max

-dp/dt

max

and NO concentration were significant higher (P0.05) and while the cTnI

apoptosis of the cardiac myocytes were significant lower in PC group (P0.05). Immunohistochemisty and PCR showed that the expression of Caveolin-3 were significant higher in the PC group than in I/R group (0.204 0±0.025 8 vs 0.156 7±0.011 3

1.319 8±0.032 9 vs 1.167 4±0.105 1

P0.05).   Conclusion  Continuous pumping of nitroglycerin at a small dosage in 1 h before ischemia exerts protective effct on myocardiocytes through activating Caveolin-3.