舒张性心力衰竭兔Ca2+调控蛋白相关基因表达的变化

目的探讨舒张性心力衰竭(DHF)时Ca2+调控蛋白相关基因表达的变化,以阐明DHF发生的分子机制.方法建立DHF兔模型,并设假手术为对照组,分别测定2组兔心肌细胞内Ca2+含量和肌浆网(SR)Ca2+-ATPase(钙泵)活性,并以定量RT-PCR和Westernblot技术检测Ca2+调控蛋白相关基因的转录和蛋白质表达水平.结果(1)DHF兔心肌细胞内Ca2+含量(μg/ml)显著高于对照组(1728±545vs633±168,P＜0.01);(2)DHF兔SR钙泵活性,细胞膜L型Ca2+通道和SR钙泵mRNA水平(μmol*mg-1*h-1)明显低于对照组(10.5±2.8vs21.1±5.7;0.75±0.11vs1.20±0.33;0.76±0.12vs1.24±0.38,P＜0.05～0.01);(3)DHF兔细胞膜L型Ca2+通道mRNA水平与左室舒张末压中度负相关(r=-0.74,P＜0.05),SR钙泵mRNA水平与左室舒张末压和左室松弛时间常数中度负相关(r分别为-0.81、-0.64,P＜0.05～0.01);DHF兔兰尼碱受体mRNA水平与左室松弛时间常数负相关(r=-0.71,P＜0.05);(4)DHF兔SR钙泵的蛋白质表达明显低于对照组(0.75±0.06vs1.02±0.09,P＜0.05).结论细胞膜L型Ca2+通道和SR钙泵mRNA和蛋白质表达减低是导致心肌细胞内Ca2+超负荷及DHF发生的重要因素.

Molecular mechanism underlying calcium handling in diastolic heart failure

OBJECTIVE: To elucidate the molecular mechanism underlying calcium handling in diastolic heart failure (DHF) from mRNA level and protein expression, including L-type calcium channel, sarcoplasmic reticulum (SR) Ca(2+)-ATPase, phospholamban, ryanodine receptor, calsequestrin. METHODS: DHF was produced in rabbits by abdominal aortic coarctation. The mRNA amounts of these calcium-handling genes were measured by RT-PCR, while the protein levels of SR Ca(2+)-ATPase and phospholamban were analyzed by Western blot analysis. RESULTS: The content of calcium was significantly increased in myocardium of rabbits with DHF than in the myocardium of sham-operated rabbits. The SR Ca(2+)-ATPase activity of DHF rabbits was significantly reduced compared with that in sham-operated rabbits (21.1 micromol.mg(-1).h(-1) +/- 5.7 micromol.mg(-1).h(-1) vs 10.5 micromol.mg(-1).h(-1) +/- 2.8 micromol.mg(-1).h(-1), P < 0.01). RT-PCR analyses showed that the steady-state level of mRNA encoding the L-type calcium channel and SR Ca2+-ATPase was decreased significantly in rabbits with DHF compared with that in the sham-operated rabbits (micromol.mg(-1).h(-1)): 0.75 +/- 0.11 vs 1.20 +/- 0.33; 0.76 +/- 0.12 vs 1.24 +/- 0.38, P < 0.05). The SR Ca(2+)-ATPase mRNA level correlated negatively well with left ventricular relaxation time constant and left ventricular end-diastolic pressure (r = -0.81, -0.64, respectively, P < 0.05 approximately 0.01); the mRNA level of L-type calcium channel correlated negatively with left ventricular end-diastolic pressure (r = -0.74, P < 0.05). The mRNA level of ryanodine receptor correlated negatively with the left ventricular relaxation time constant too (r = -0.71, P < 0.05). Protein level of SR Ca(2+)-ATPase was significantly lower in rabbits with DHF than in the sham-operated rabbits (0.76 +/- 0.6 vs 1.02 +/- 0.09, P < 0.05), whereas the protein level of phospholamban was unchanged. CONCLUSION: The L-type calcium channel and SR Ca(2+)-ATPase were down regulated in DHF. These changes may be a contributory factor for DHF.