体外循环对兔骨骼肌葡萄糖转运蛋白4和胰岛葡萄糖转运蛋白2的影响

目的观察体外循环(Cardiopulmonary bypass,CPB)对兔骨骼肌葡萄糖转运蛋白4(Glucose transporter 4,GLUT4)和胰岛葡萄糖转运蛋白2(GLUT2)的影响,探讨CPB中高血糖的可能机制。方法取健康成年新西兰大白兔24只,随机分为正常对照组(N组)和CPB组(C组),每组12只。N组不行CPB,C组行CPB。两组分别于麻醉后即刻(T1)、主动脉阻断即刻(T2)、主动脉开放5min(T3)、主动脉开放35min(T4)和主动脉开放75min(T5)采集动脉血液,氧化酶法检测血糖水平,放免法检测胰岛素水平;免疫组织化学法检测主动脉开放5min和75min时骨骼肌总GLUT4和细胞膜上GLUT4的转位表达及开放75min时胰岛细胞GLUT2的表达。结果与T1比较,两组T2～T5的血糖和胰岛素水平均显著升高(P<0.05);C组T2～T5的血糖和胰岛素水平较N组显著升高(P<0.05);主动脉开放5min和75min时,C组骨骼肌总GLUT4和细胞膜上GLUT4的转位表达均显著下调(P<0.05);主动脉开放75min时,胰岛细胞GLUT2的表达显著上调(P<0.05);C组主动脉开放75min比5min时,骨骼肌总GLUT4和细胞膜上GLUT4的转位表达均显著上调(P<0.05)。结论兔CPB中高血糖可能与骨骼肌GLUT4表达下调和转位障碍有关。胰岛细胞GLUT2表达上调可能使胰岛素分泌增加,但增加的胰岛素并不能完全代偿高血糖。

Effect of Cardiopulmonary Bypass on Glucose Transporter 4 in Skeletal Muscle and Glucose Transporter 2 in Islets of Rabbits

Objective To observe the effect of cardiopulmonary bypass(CPB) on the glucose transporter 4(GLUT4)in skeletal muscle and GLUT 2 in islets of rabbits and investigate the potential mechanism of hyperglycaemia in CPB. Methods Twenty-four New Zealand rabbits were divided into normal control(N)and CPB(C)groups, 12 for each. Rabbit model of CPB was established by using the rabbits in C group. The arterial blood samples of rabbits in the two groups were collected immediately after narcosis(T1), immediately after aortic cross-clamping(T2)as well as 5(T3), 35(T4)and 75 min(T5)after reperfusion and determined for blood glucose by oxidase test and for insulin by radioimmunoassay. The transposition expressions of total GLUT4 of skeletal muscle and GLUT4 on cell membrane 5 and 75 min as well as expression of GLUT2 in islet cells 75 min after reperfusion were determined by im- munohistochemical assay. Results Both the blood glucose and insulin levels at T2～T5 of the two groups increased significantly (P < 0. 05)as compared with those at T1, and were significantly higher in group C than in group N (P < 0. 05). Both the transposition expressions of total GLUT4 of skeletal muscle and GLUT4 on cell membrane of rabbits in group C 5 and 75 min after reperfusion were down-regulated significantly(P < 0. 05), while the expression of GLUT2 in islet cells 75 min after reperfusion was up-regulated significantly(P < 0. 05). However, both the transposition expression levels of total GLUT4 of skeletal muscle and GLUT4 on cell membrane of rabbits in group C 75 min after reperfusion were significantly higher than those 5 min after reperfusion. Conclusion The hyperglycaemia in CPB of rabbits might be associated with the down-regulation of expression and disturbance of transposition of GLUT4 in skeletal muscle. Though the up-regulation of GLUT2 expression in islet cells might increase the secretion of insulin, the high blood glucose level could not be compensated completely by the increased insulin.