| Insulin is a hormone that contains 51 amino acid and is synthesized by P cell in pancreas. In recent years, because some cardiovasular syndromes often occur on diabetic patients, the effects of insulin on cardiovasular system drew researchers' attention. Glucose-insulin-potassium solution (GIK cocktail) had been used on the clinic treatment to acute ischemia/reperfusion injury for forty years, but the mechanisms of the effect keep unknown.The aims of this study were to (1) observe the protective effects of GIK solution on rabbits acute ischemia/reperfusion heart, (2) try to investigate its potential mechanisms and (3) determine the protective effects of insulin in GIK solution. Our experimental results are follows:1. The effects of insulin on normal heart and blood vessel1.1 The effects of insulin on normal heartTo expose the heart, left ventricular pressure (LVSP,LVEDP) and?dp/dtmax were measured with a catheter tip pressure tranducer inserted into left ventricular. A catheter was inserted into the left femoral artery to measure the mean aortic blood pressure (MAP) and another catheter was introduced into leftfemoral vein to infuse insulin (lOOu/L) or vehicle(0.9% saline). By contrast, we found that insulin could increase the contractile function of heart, enhance LVSP, + dp/dtmax and reduce LVEDP, - dp/dtmax. After 2min of infusing, LVSP, LVEDP and ?dp/dtmax between GIK group and insulin group show difference significantly (insulin group: LVSP 167.0+14.44, + dp/dtmax +6394 + 873, -dp/dtmax -3775 + 305, P<0. 05 vs control group),, There were not difference in LVEDP and MABP between insulin and control groups ( insulin group: LVEDP 6.3 ?.1, MABP 98.6 + 13.4; control group: LVEDP 5.8 ?.9, MABP 94.3 ?1. 9).1.2 The effects of insulin on the isolated single cardiocytesIsolating the cardiocytes from adult rat's heart and detecting its contractile function on the lonOptix single cell detecting system. 10"4 u/L insulin can strengthen cardiocytes' contractile function(13.4眑. 9%). But flushing could not recover the cardiocyte to the normal immediately (duration beyond 10 min).1.3 The diastolic effects of insulin on the isolated arteryInsulin (0.1-100 u/L) had a significant dose-dependent relaxation effect on rat abdominal artery. The relaxation effect of insulin on rat abdominal artery was endothelium-dependent.2. The protective efects of insulin on ischemia/reperfusion heart Myocardial ischemia reperfusion model in rabbits were made and were divided into three groups randomly. Rabbits were subjected to 40 min of regional myocardial ischemia and 3 h of reperfusion. GIK(glucose 150 g/L, insulin 100 u/L, potassium 80 mmol/L), insulin(100 u/L),Vehicle(9 g/L NaCl)were given i.v. 30 min before ischemia respectively (1.2 mL/h). The index of myocardial function was recorded and analyzed. The activities of CK andLDH were detected. Infarced sizes in heart were determined by dual staining with Evans-blue and TTC. The results show that all indexes related to injure, namely LVEDP, 眃p/dtmax, CK, LDH and the ratio of myocardial ischemic and necrotic area, show injure attenuation in GIK and insulin groups in comparison with control group. Due to above results, we drew the conclusion that during myocardial ischemia reperfusion, GIK not only provides energy, but also insulin in it plays a critical role in protecting ischemic cardiocytes.
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