Lamers J M, Duncker D J, Bezstarosti K, McFalls E O, Sassen L M, Verdouw P D
Department of Biochemistry, Faculty of Medicine and Health Sciences, Erasmus University Rotterdam, The Netherlands.
Cardiovasc Res. 1993 Mar;27(3):520-4. doi: 10.1093/cvr/27.3.520.
The aim was to determine whether changes in sarcoplasmic reticular Ca2+ transport activity and the degree of phosphorylation of phospholamban of "stunned" myocardium are involved in the reversible depression of contractile function.
In anaesthetised open chest swine, stunning was induced by subjecting the myocardium perfused by the left anterior descending coronary artery to two cycles of 10 min of occlusion and 30 min of reperfusion. Before and after stunning, systemic haemodynamic variables and regional myocardial function and perfusion were determined, while biopsies were taken for determination of the content of high energy phosphate compounds. Sarcoplasmic reticular function (ATP dependent Ca2+ transport and phosphorylation of phospholamban) of the stunned and control myocardium was determined at the end of the stunning protocol.
In the stunned myocardium the segment length shortening decreased from 17.4(SD 4.0)% to 3.5(4.4)%, while perfusion was 38% less than at baseline. ATP and total adenine nucleotide levels of the stunned myocardium were about 35% lower than in the control myocardium, but the energy charge was normal as creatine phosphate levels had increased by 66% over the content determined at baseline. Ca2+ uptake by the sarcoplasmic reticulum isolated from the stunned region was 17% (p < 0.05) higher than Ca2+ uptake from the control region [1240(303) and 1450(280) nmol.min-1.mg-1 protein, respectively]. In the presence of exogenous cyclic AMP dependent protein kinase the amount of 32P incorporated into phospholamban was similar for both myocardial regions.
In this model of stunned porcine myocardium, the phosphorylation state of phospholamban was unchanged, but Ca2+ uptake by the sarcoplasmic reticulum was slightly increased. The results indicate that a change in active Ca2+ transport by the sarcoplasmic reticulum is most likely not to be the principal cause of contractile dysfunction of stunned myocardium.
确定“顿抑”心肌肌浆网Ca2+转运活性的变化及受磷蛋白的磷酸化程度是否与收缩功能的可逆性降低有关。
在麻醉开胸猪中，通过对左前降支冠状动脉灌注的心肌进行两个周期的10分钟闭塞和30分钟再灌注来诱导顿抑。在顿抑前后，测定全身血流动力学变量、局部心肌功能和灌注，同时取活检组织测定高能磷酸化合物的含量。在顿抑方案结束时，测定顿抑心肌和对照心肌的肌浆网功能（ATP依赖性Ca2+转运和受磷蛋白的磷酸化）。
在顿抑心肌中，节段长度缩短从17.4（标准差4.0）%降至3.5（4.4）%，而灌注比基线时减少38%。顿抑心肌的ATP和总腺嘌呤核苷酸水平比对照心肌低约35%，但能量负荷正常，因为磷酸肌酸水平比基线时测定的含量增加了66%。从顿抑区域分离的肌浆网对Ca2+的摄取比对照区域高17%（p<0.05）[分别为1240（303）和145(280)nmol·min-1·mg-1蛋白质]。在外源性环磷酸腺苷依赖性蛋白激酶存在的情况下，两个心肌区域中掺入受磷蛋白的32P量相似。
在这个猪顿抑心肌模型中，受磷蛋白的磷酸化状态未改变，但肌浆网对Ca2+的摄取略有增加。结果表明，肌浆网主动Ca2+转运的变化很可能不是顿抑心肌收缩功能障碍的主要原因。
