The Study Of Influences And Mechanism Of Verapamil On Ischemia/Reperfusion Injury In Cardiomyocytes Of Streptozotocin-induced Diabetes Mullitus Rats

Objectives:To investigate the effects and mechanism of verapamil preventing ischemia/reperfusion (I/R) injury via observing the cardiac performance and intracellular free [Ca2+]i as soon as L-type calcium current (ICa-L) in cardiomyocytes of diabetes mellitus rats.MethodsDiabetes rats by streptozotocin-induced were fed verapamil (8mg/kg/d) from 6 tol4 wk of age.The hearts models of I/R in vitro rats which randomly divided into normal control group, diabetes group, verapamil control and diabetes groups were setup to observe the changes of heart function through using Langendorff-perfusion system. The fluorescence intensity of intracellular Ca2+was detected with Flup-3/AM loading by the laser scanning confocal microscope. The ICa-L was recorded via whole-cell patch clamp technique in enzymatically dissociated single rat ventricular myocytes.Results1 With I/R injury of the vitro rat hearts in diabetes group, the valures of left ventricular developed pressure (LVDP), diastolic end pressure (LVEDP), the maximum rising rates of left ventricular pressure (dp/dtmax) and coronary arterial flow (CF) were all significantly decreased, and the maximum dropping rates of left ventricular pressure (dp/dtmin) were increased (compared with normal control group, P<0.01, respectively). But some parameters mentioned above such as LVDP, LVEDP, dp/dtmax, CF were increased, and dp/dtmin was obviously decreased in verapamil diabetes group (compared with diabetes group, P<0.01, respectively).2 The fluorescence intensities of intracellular free Ca2+ in cardiomyocytes of diabetes rats were markedly stronger after influence of I/R injury (compared with normal control group, P<0.01). Under every command potential, the current density of ICa-L was significantly decreased, and the current-voltage (Ⅰ-Ⅴ) curve was changed up to the top, as soon as the peak clamp potential was-30mV with same I/R condition in diabetes rats. In verapamil diabetes group, The fluorescence intensities of intracellular free Ca2+ were significantly reduced in I/R injury procedure (compared with diabetes group, P<0.01). ICa-L were partly recovered near normal control group, and I-V curve was changed among normal control and diabetes group. The peak clamp potential was -20mV. When clamp voltage was -20mV, the current densities of ICa-L were significantly decreased from (-8.17±2.07) pA/pF in normal control group to (-3.21±0.54) pA/pF in diabetes group (P<0.01), and (-7.14±2.17) pA/pF in verapamil control group (compared with normal control, P>0.05), and (-6.81±0.76) pA/pF in verapamil diabetes group(compared with normal group, P<0.05, and with diabetes group, P<0.01, and with verapamil control group, P>0.05).ConclusionThe poor heart function was tightly correlate to that the [Ca2+]i was increased and ICa-L was decreased with I/R injury in diatetes rat hearts. Verapamil-treated in long time could significantly inhibit I/R injury induced the severely cardiac performance in diabetes rats, which was attributed to that verapamil might adjust ICa-L influx, and normalize the balance of intercellular [Ca2+]i, as soon as blocked the Ca2+ overload trigged by effects of Ca2+induced Ca2+ release in diabetes cardiomyocytes...