A correlative study of myocardial relaxation, intracellular Ca^<2+> concentration, expression of the sarcoplasmic reticulum Ca^<2+>-ATPase.

据报道，细胞内Ca^<2+>-hadling随着心肌肥大而沿着改变。为了更好地表征肥大心肌细胞中Ca^2+处理的改变，将培养的鸡胚（10日龄）心室肌细胞暴露于10%胎牛血清（FCS）24小时，建立了心肌肥大的体外模型。在FCS处理组中，与未处理对照组相比，RNA和蛋白质含量均增加约25%（p<0.05，n=4），而细胞数量无任何变化。与对照组相比，FCS治疗组的收缩期[Ca^&lt;2+&gt;] i峰值（用indo-1测量）较低（753 <plus-minus>103 vs.950 <plus-minus>142 ms，p&lt;0.050，n=4），Ca^&lt;2+&gt;瞬变衰减的T &lt;12&gt;较长（163 <plus-minus>7 vs.132 <plus-minus>12 ms，p&lt;0.05，n=4）。Thapsigargin（1 mM）是肌浆网Ca^&lt;2+&gt;-ATP酶的抑制剂，可引起收缩期[Ca^&lt;2 +&gt;]_i峰值降低，T_&lt;1/2&gt;延长，其结果与对照组比较，差异有统计学意义（P &lt;0.05）。 ...更多信息 FCS治疗组为对照组。RNA印迹分析显示，FCS处理组编码SR Ca^&lt;2+&gt;-ATP酶的mRNA的相对丰度（用激光密度计测定）显著降低（<plus-minus>对照组的41.8 ± 3.8%，p&lt;0.05，n=4）。FCS处理组的Na^+/Ca^&lt;2+&gt;交换体mRNA水平也降低（<plus-minus>为对照组的35.0 ± 4.3%，p&lt;0.05，n=4）。FCS治疗组在无Na^+溶液（包括10 mM咖啡因（ONa+Caf），可阻断Na^+/Ca^2+交换体和SR）灌注期间[Ca^2+] i的稳态水平较低（338 <plus-minus>30对806 <plus-minus>129 nM，p&lt;0.05，n=4）。当维拉帕米（1 mM）灌注后，这些差异被减少（294 <plus-minus>- 33与282 - <plus-minus>35 nM，NS）。用1 mM钒酸盐（用作肌膜Ca^2+-ATP酶的抑制剂）预处理后，再灌注ONa+Caf也显示出类似的结果。另一方面，维拉帕米预处理在ONa+Caf灌注期间，FCS处理组和对照组之间的稳态[Ca^&lt;2+&gt;]_i没有显著差异。这些数据表明，在我们的体外模型中，Ca^&lt;2+&gt;处理的改变沿着细胞肥大。这些Ca^2+处理的变化可能包括电压依赖性Ca^2+通道以及SR Ca^2+-ATP酶和Na^+/Ca^2+交换器的下调。少

Intracellular Ca^<2+>-hadling has been reported to be altered along with myocardial hypertrophy. To well characterize the altered Ca^<2+>-handling in hypertrophied cardiac myocytes, an in vitro model of myocardial hypertrophy was created in cultured chick embryo (10-day-old) ventricular myocytes by exposure to 10% fetal calf serum (FCS) for 24 hours. In the FCS-treated group, both RNA and protein contents increased by about 25% as compared with the untreated control group (p<0.05, n=4), without any changes in cell number. The peak systolic [Ca^<2+>]_i (measured with indo-1) was lower (753<plus-minus>103 vs. 950<plus-minus>142 ms, p<0.050, n=4) and T_<1/2> of the decay of the Ca^<2+> transients was longer (163<plus-minus>7 vs.132<plus-minus>12 msec, p<0.05, n=4) in the FCS-treated group than in the control group. Thapsigargin (1 mM), an inhibitor of the sarcoplasmic reticulm (SR) Ca^<2+>-ATPase, induced a decrease in the peak systolic [Ca^<2+>]_i with an elongation of the T_<1/2> as obs … More erved in the FCS-treated group. RNA blot analysis revealed that the relative abundance of mRNA (determined by laser densitometry) encoding the SR Ca^<2+>-ATPase was decreased significantly (41.8<plus-minus>3.8% of the control group, p<0.05, n=4) in the FCS-treated group. The levels of Na^+/Ca^<2+> exchanger mRNA were also diminished in the FCS-treated group (35.0<plus-minus>4.3% of the control, p<0.05, n=4). Steady-state levels of [Ca^<2+>]_i during perfusion with Na^+-free solution including 10 mM caffeine (ONa+Caf), which blocks Na^+/Ca^<2+> exchanger and SR,was lower in the FCS-treated group (338<plus-minus>30 vs. 806<plus-minus>129 nM,p<0.05, n=4). When verapamil (1 mM) perfusion was followed, these differences were diminished (294<plus-minus>33 vs. 282<plus-minus>35 nM,NS). Perfusion with ONa+Caf after pretreatment with 1 mM vanadate (used as an inhibitor of the sarcolemmal Ca^<2+>-ATPase) also showed similar results. On the other hand, pretreatment with verapamil caused no significant differences in the steady-state [Ca^<2+>]_i during perfusion with ONa+Caf between the FCS-treated and control groups. These data suggest that the alterations in Ca^<2+>-handling occur along with cellular hypertrophy in our in vitro model. These changes in Ca^<2+>-handling may include down regulation of voltage-dependent Ca^<2+> channel as well as the SR Ca^<2+>-ATPase and Na^+/Ca^<2+> exchanger. Less