Study On The Delayed Protective Effect Of Noninvasive Limb Ischemic Preconditioning Against Myocardial Injury In Rats

Objective: To study on the delayed protective effect of noninvasive limb ischemic preconditioning against myocardial injury in rats.Method: After rat anesthetized with chloral hydrate, the left hind limb was trapped with canula of modified noninvasive sphygmomanometer. After that, to stick pulse transduce to arteria dorsalis pedis. Asphygmia indicated blockade of arteria femoralis, which lasted 5 min, while pulse appearance indicated reperfusion, which last 5 min, the procedure was operated 3 circles. Thirty healthy male Wistar rats (240-260 g) were divided randomly into 3 groups. (1) I/R group, only 30 min ischemia and 120 min reperfusion of LAD was conducted. (2) IP group, 3 circles of 5-min periods of I/R followed by 30 min ischemia and 120 min reperfusion of LAD. (3) NLIP group, 3 circles of 5-min periods of left hind limb I/R, once time every day for 3 days. On the forth day, 30 min ischemia and 120 min reperfusion of LAD was done. shorten IS (43.2±15.4 and 39.5±13.6 mg, P<0.01), decrease IS/AAR (28.6±9.5 and 25.4±8.7%, P<0.01), and myocardial injury was moderate: the swelling was not apparent, no fragmentation, only a little inflammatory cell infiltrated.3. Influence of NLIP on the biochemistry after IRICompared with I/R group (118.2±36.4 U/L and 2.66±1.00 ng/ml), IP and NLIP could decrease CK-MB and cTnI (80.4±33.4 and 85.1±27.9 U/L, P<0.05; 1.31±0.81 and 1.20±0.79 ng/ml, P<0.01). Meanwhile, compared with I/R group (300±49 NU/ml), IP and NLIP could elevate SOD activity(366±72 and 388±67 NU/ml, P<0.05 and P<0.01).4. Influence of NLIP on apoptosis of myocardium after IRIThe apoptosis rate in ischemic myocardium of I/R group was very high (6.21±2.12%), but Bcl-2/Bax was very low (0.66±0.03). Compared with I/R group, the apoptosis rate was decreased significantly (5.30±0.81and 4.82±1.15%, P<0.01), but Bcl-2/Bax was very high (1.44±0.08 and 1.51±0.09,P<0.01). Results of TUNEL and immunohistochemistry were in coincidence with above.5. Influence of NLIP on MMPs after IRIExpression of MMP-2 (21.33±2.34%) and MMP-9 (16.41±2.92%) was high, and TIMP-1 (10.79±1.15%) was low in ischemic myocardium of I/R group. Compared with I/R group, expression of MMP-2 (12.35±1.10 and 12.55±1.08%, P<0.01) and MMP-9 (9.31±1.08 and 8.76±1.12%, P<0.01) was decreased and expression of TIMP-1 (15.11±2.58 and 16.59±2.98%,P<0.01) was increased in IP and NLIP group. Positive particle distributed in the endochylema of myocardial cell and vascular endothelial cell, sometimes in the interstitial cell. Results of RT-PCR were in coincidence with immunohistochemistry.6. Influence of NLIP on blood fibrinolysis factor after IRIThe activity of t-PA descended in progress during ischemia and reperfusion, but the activity of PAI-1 advanced in progress in every group. After reperfusion, the activity of t-PA and PAI-1 was 1.01±0.33 U/ml and 27.11±0.63 AU/ml respectively. Compared with I/R group, IP and NLIP could prevent t-PA activity (1.98±0.46 and 1.89±0.44 U/ml, P<0.01) from decreasing and PAI-1 (25.42±0.56 and 22.01±0.45 AU/ml, P<0.01) from increasing.Conclusion:1. NLIP could protect heart against IRI via reducing ST-segment, delaying onset, shortening duration and decreasing incidence rate of VA, which is nearly to the level of early cardiac ischemic preconditioning.2. NLIP could decrease IS and improve morphological changes caused by IRI.3. NLIP could protect cardiac cell against IRI through reducing the leakage of cardiac muscle enzyme, elevating SOD activity.4. NLIP could prevent myocardium from apoptosis caused by IRI and improve anomaly expression of the controlling gene of Bcl-2 and Bax.5. NLIP could decrease the expression of MMPs, increase the expression of TIMP caused by IRI, which prevented cardiac matrix from degrading and maintain myocardial normal structure.6. NLIP could improve the system of fibrinolysis and anti-fibrinolysis, which maybe the one of mechanisms of protection.