The Effects Of Simvastatin On Expressions Of Calcium Channel During Cardiac Hypertrophy And Its Mechanism

Objective: To investigate the effects of SIM on calcium channel during cardiac hypertrophy and the related mechanism.Methods: (1) In vivo experiment: Male SD(sprague-dauley)rats were divided into five groups randomly and made model of over-loading myocardial hypertrophy, then given Verapamil hydrochloride (Ver, 10mg·kg·d ), simvastatin (SIM, 10mg·kg·d ) alone or given simvastatin (10mg·kg·d ) and mevalonic acid (MVA, 50mg·kg·d ) for 4 weeks. Male Sham rats were the non-hypertrophic control. The arterial systolic pressure was measured using the tail-cuff method at special time. After 4 weeks'treatment, cardiac geometry and function was evaluated and ultrasonic integrated backscatter was acquired at interventricular septum (IVS) and left ventricular posterior wall (LVPW) with the echocardiographic system. Then, rats were sacrificed and hearts were harvested. Total protein content of the left ventricle was determinated with micro-Coomassie Brilliant Blue; Weighed and calculated heart weight index to compare the effects on myocardial hypertrophy; the activity of superoxide dismutase (SOD) and Malondialdebyde (MDA) were detected to discover the change of oxygen free radical. Meanwhile, the gene expression of L-type calcium channel subunit,αC mRNA, and T-type calcium channel subunit,αG,αH mRNA were detected by RT-PCR. The expression ofαC,αG andαH were detected by western blot. (2) Myocardial cell culture experiment: Cardiomyocytes were divided into five groups randomly, and neonatal rat cardiac hypertrophy was induced by AngⅡ. Total protein content was measured by Lowary's method and the cell surface area was measured by phase contrast microscope and image analysis system(HJ2000); CCK-8 method was used to observe the viability of myocardiocytes; The expression ofαC,αG andαH were detected by western blot; Intracellular Ca were measured with Fluo-3/ AM under confocal laser microscope.Results:1. The heart systolic blood pressure(SBP),heart weight/body weight (HW/BW),left ventricle weight/heart weight(LVW/BW),thickness of IVS and LVPW,total protein content of the left ventricle increased and FS,EF decreased significantly in abdominal aorta constricted induced cardiac hypertrophic rats. But these effects could be inhibited by the pretreatment of SIM or Ver.2. The mRNA expression and protein ofαG orαH were at most absent in Sham rats, but strongly increased in the abdominal aorta constricted rats and significantly inhibited by the pretreatment of SIM or Ver. But the mRNA expression and the protein level of L-type calcium channelα-subunitαC was no significant difference between each group.3. Banding the abdominal aorta of rats could decrease the SOD activities, increase the MDA concentrations and myocardial antioxidant capacity breakdown. But these effects could be inhibited by the pretreatment of SIM or Ver.4. The total protein content and cell surface area of cardiomyocytes increased significantly and the cardiomyocyte viability decreased after AngⅡtreatment. SIM inhibited these effects of AngⅡ, which was similar with Ver.5. AngⅡsignificantly activated the expression of T-type calcium channelα-subunitα1G orα1H and was inhibited by SIM or Ver. But the protein content of L-type calcium channelα-subunitαC was no significant difference between each group.6. AngⅡinduced myocardial hypertrophy, then caused intracellular calcium overload. In the presence of SIM, AngⅡ-elicited calcium influx was inhibited remarkably with a concentration-dependent manner and it produced the best effect at 10 ~10μmol/L, which was similar with the effect of calcium channel blocker Ver.Conclusions:1. Constraction of abdominal aortic can induce cardiac hypertrophy in rats. SIM can prevent cardiac hypertrophy induced by abdominal aortic binding, which may be related to the inhibition of T-type calcium channel subunitαG,αH re-expression, but had nothing to do with the expression of L-type calcium channel subunitαC.2. AngⅡcan induce cultural rat cardiomyocyte hypertrophy. SIM can inhibit AngⅡ-induced cardiomyocyte hypertrophy, which may be related to the inhibition of the increasing of T-type calcium channel subunitαG,αH, and meanwhile to the inhibition of calcium overloading, but was independence with the expression ofαC subunit.