Matsui H, MacLennan D H, Alpert N R, Periasamy M
Department of Molecular Physiology and Biophysics, University of Vermont College of Medicine, Burlington 05405.
Am J Physiol. 1995 Jan;268(1 Pt 1):C252-8. doi: 10.1152/ajpcell.1995.268.1.C252.
Pressure overload (PO)-induced cardiac hypertrophy in rabbits has been utilized extensively to study alterations in systolic and diastolic functions of the heart. In earlier studies we showed that the levels of mRNA encoding two important sarcoplasmic reticulum (SR) proteins, the cardiac/slow-twitch muscle Ca(2+)-ATPase (SERCA2a) and phospholamban, were decreased in PO rabbit hearts. In this study, we analyzed the expression of the Ca(2+)-release channel (ryanodine receptor), calsequestrin, SERCA2a, and phospholamban in PO-induced cardiac hypertrophy after 2, 4, 8, and 16 days of pulmonary artery banding. Northern blot and slot blot analyses showed that the steady-state level of mRNA encoding the cardiac ryanodine receptor, SERCA2a, and phospholamban was decreased significantly as early as 2 days after PO. In 16-day PO hearts, SERCA2a mRNA was reduced to 7.9 +/- 3.4% (P < 0.05), phospholamban mRNA was reduced to 15.9 +/- 6.5% (P < 0.05), and ryanodine receptor mRNA was reduced to 49.2 +/- 23.6% (P < 0.05). In this study, calsequestrin mRNA levels were also reduced to 29.9 +/- 15.2% by day 16 (P < 0.05). ATP-dependent Ca2+ uptake was reduced to 78% (P < 0.05); in contrast, the steady-state formation of ATPase phosphoenzyme was reduced to 81% of control (P < 0.05) and Ca(2+)-ATPase protein was reduced to 78% of control (P < 0.05) in crude SR vesicles or total muscle homogenate obtained from 16-day PO hearts. On the basis of these data, we propose that decreases in the expression of SR proteins may contribute to dysfunctions seen in systolic and diastolic properties of the hypertrophied myocardium.
兔压力超负荷（PO）诱导的心脏肥大已被广泛用于研究心脏收缩和舒张功能的改变。在早期研究中，我们发现编码两种重要肌浆网（SR）蛋白，即心脏/慢肌钙（2+）-ATP酶（SERCA2a）和受磷蛋白的mRNA水平在PO兔心脏中降低。在本研究中，我们分析了肺动脉束带2、4、8和16天后PO诱导的心脏肥大中钙释放通道（雷诺丁受体）、肌集钙蛋白、SERCA2a和受磷蛋白 的表达。Northern印迹和狭缝印迹分析表明，早在PO后2天，编码心脏雷诺丁受体、SERCA2a和受磷蛋白的mRNA稳态水平就显著降低。在PO 16天的心脏中，SERCA2a mRNA降至7.9±3.4%（P<0.05），受磷蛋白mRNA降至15.9±6.5%（P<0.05），雷诺丁受体mRNA降至49.2±23.6%（P<0.05）。在本研究中，到第16天时肌集钙蛋白mRNA水平也降至29.9±15.2%（P<0.05）。ATP依赖性钙摄取降至78%（P<0.05）；相反，在从PO 16天的心脏获得的粗制SR囊泡或全肌肉匀浆中，ATP酶磷酸化酶的稳态形成降至对照的81%（P<0.05），钙（2+）-ATP酶蛋白降至对照的78%（P<0.05）。基于这些数据，我们提出SR蛋白表达的降低可能导致肥厚心肌收缩和舒张特性中出现的功能障碍。
