[Apoptosis mechanism of intralipid postconditioning to reduce ischemia reperfusion injury of isolated rat hearts].

OBJECTIVE

To test the effect of intralipid, a solution containing soybean oil, egg phospholipid and glycerol, on protecting perfused rat hearts against ischemia/reperfusion injury (IR) and to explore possible cardiomyocyte apoptosis mechanism involved.

METHODS

Twenty Sprague-Dawley rtas were perfused with Kreb-Henseleit buffer on Langendorff apparatus. The rats were randomly allocated to 4 groups. The control group of rats were perfused for 3 hours and 50 minutes without cardiplegia ischemia. The hearts of the other three groups of rats (I-preC, I-postC, and ISCH) were subjected to 45 minutes of ischemia and 3 hours of reperfusion. The I-preC group was pre-treated with 15 minutes of intralipid followed by 15 minutes of wash out. The I-postC group was treated by 15 minutes of intralipid at the onset of reperfusion. The ISCH group served as untreated ischemic control. The LVDP (Left Ventricular Developed Pressure) and HR were measured before and after reperfusion. The LVW was calculated as LVDP x HR. LDH were measured 20 minutes after perfusion and 60 minutes after reperfusion. TUNEL staining was used for identification of apoptotic cells. After 3 hours of reperfusion, the changes of expressions of Bcl-2 and Bax were examined by Western Blotting.

RESULTS

Slightly mechanic function attenuation and low LDH release were found in the control group, along with little apoptosis. By contrast, significantly decreased mechanical function and more cardiocyte apoptosis were found in the ISCH group. Intralipid postconditioning improved LVW and reduced LDH activity significantly. The improvement was accompanied by increased protein expression of Bcl-2 and decreased Bax protein level. Intralipid preconditioning decreased LDH level only. No significant differences in protein level of Bcl-2 and Bax were found between the I-preC and ISCH group.

CONCLUSION

Intralipid postconditioning improves cardiac mechanical performance through inhibiting cardiocyte apoptosis and reducing LDH activity. Intralipid preconditioning reduces LDH level but does not inhibit cardiocyte apoptosis.