维拉帕米对链脲佐菌素诱导糖尿病大鼠心肌缺血再灌注损伤的影响及机制

目的 观察维拉帕米(Ver)对糖尿病大鼠心肌缺血再灌注(L/R)后心功能,细胞内[Ca2+]i及L-型钙电流(ICa-L)影响,探讨其防治糖尿病心肌I/R损伤的作用和机制.方法 链脲佐菌素诱导糖尿病大鼠后的第6～14周龄给予Ver(8 mg·kg-1·d-1)灌胃,Langendorff系统复制大鼠心肌I/R模型,观察不同实验组的心功能变化,双酶法急性分离各组心肌细胞,激光扫描共聚焦显微镜加Fluo-3/AM荧光染色技术和全细胞膜片钳技术分别观察心肌细胞内Ca2+荧光强度和ICa-L大小.结果 (1)与糖尿病组相比,Ver糖尿病组的左心室发展压(91.3±4.6)mm Hg(1 mm Hg=0.133kPa)、舒张末压(1535±280)mm Hg、收缩压最大上升速率(5833±256)mm Hg/s、冠状动脉流量(13.7±0.9)ml/min均明显增加(P<0.01),收缩压最大下降速率(3504±319)mm Hg/s明显减少(P<0.01).(2)Ver糖尿病组心肌细胞内Ca2+荧光强度(155.6±10.9)nmol/L与糖尿病组(245.2±17.5)nmoL/L相比明显减弱(P<0.01).(3)当指令电位为+20 mV时,Ver糖尿病组心肌细胞ICa-L为(-6.81±0.76)pA/pF,与正常对照组[(-8.17±2.07)pA/pF]相比减小(P<0.05),与糖尿病组[(-3.21±0.54)pA/pF]相比增加(P<0.01),与Ver对照组[(-7.14±2.17)pA/pF]相比减少(P>0.05).Ver糖尿病组的I-V曲线显著低于糖尿病组,最大峰值在+20 mV.结论 Ver可以明显改善I/R损伤引起的糖尿病大鼠心功能下降,其机制可能是Ver调控心肌细胞膜上ICa-L内流大小,优化心肌细胞内[Ca2+]i平衡,避免I/R时心肌细胞内Ca2+超载.

Influences and mechanism of verapamil on ischemia/reperfusion injury in cardiomyocytes of streptozotocin-induced diabetes mullitus rats

Objective To investigate the effects and mechanism of verapamil preventing ischemia/reperfusion (I/R) injury by cardiac performance intracellular free [Ca2+]1 and L-type calcium current (ICa-L) in cardiomyocytes of diabetes mellitus rats. Methods Diabetic rats were streptozotocin-induced and recived verapamil(8 mg·kg-1·d-1)from 6-14 weeks old.The in vitro heart models of I/R rats were randomly divided into normal control group diabetes group, verapamil control group. the changes of heart functions were observed through a Langendorff-perfusion system. The fluorescence intensity of intracellular Ca2+ was detected with Fluo-3/AM loading by laser scanning confocal microscope. ICa-L was recorded by the whole-cell technique of patch clamp in enzymatically dissociated single rat ventricular myocytes. Results (1) In verapamil diabetes group, the values of left ventricular developed pressure [(91.3 ±4.6) mm Hg],diastolic end pressure [(1535 ±280)mm Hg], the maximum rising rates of left ventricular pressure [(5833 ±256) mm Hg/s] and coronary arterial flow [(13.7 ± 0.9) mL/min] were all significantly increased, and the maximum dropping rates of left ventricular pressure [(3504 ± 319)mm Hg/s] was obviously decreased (compared with diabetes group, P < 0.01, respectively). (2) The fluorescence intensities of intracellular free Ca2+ [(155.6 ± 10.9) nmoL/L] in verapamil diabetes group were significantly reduced compared with diabetes group (245.2 ± 17. 5 nmol/L, P < 0.01). (3) When clamp voltage was - 20mV, ICa-L was (- 6.81 ±0.76)pA/pF in verapamil diabetes group(compared with normal group (-8.17±2.07) pA/pF, P<0.05,and with diabetes group (-3.21±0.54) pA/pF, P <0.01, and with verapamil control group (-7.14 ±2.17)pA/pF, P>0.05). The current-voltage curve was changed to the lower position with -20mY of peak clamp potential in verapamil diabetes group compared with diabets group. Conclusion A poor heart function is closely correlated with a rising [Ca2 +] i and a declining ICa-L associated with I/R injury in diabetic rats hearts. Along-term verapamil therapy may significantly improve the severe cardiac impairment. The mechanism is probably attributed to the fact that verapamil can adjust ICa-L influx, normalize the balance of intercellular [Ca2 +]i, and block the Ca2+ overload trigged by the effects of Ca2+ -induced Ca2+ release in diabetic cardiomyocytes.