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+>-处理随心肌肥大而改变。为了更好地表征肥大心肌细胞Ca^<2+>处理的改变，我们在培养的10日龄的鸡胚心室肌细胞中暴露于10%胎牛血清（FCS） 24小时，建立了心肌肥大的体外模型。与未处理对照组相比，fcs处理组的RNA和蛋白质含量均增加了约25% (p<0.05, n=4)，但细胞数量没有变化。fcs治疗组收缩期[Ca^<2+>]_i（用indo-1测量）峰值较对照组低（753<正负>103 vs 950<正负>142 ms, p<0.050, n=4）， Ca^<2+>瞬态衰减的T_<1/2>更长（163<正负>7 vs 132<正负>12 msec, p<0.05, n=4）。肌浆网（SR） Ca^<2+>- atp酶抑制剂Thapsigargin （1 mM）诱导收缩压峰值[Ca^<2+>]_i降低，延长T_<1/2>。RNA印迹分析显示，fcs处理组编码SR Ca^<2+>- atp酶的mRNA相对丰度（激光密度测定）显著降低（41.8<正负>3.8%,p<0.05, n=4）。fcs处理组Na^+/Ca^<2+>交换mRNA水平也降低（35.0<正负>为对照组的4.3%,p<0.05, n=4）。含有10 mM咖啡因（ONa+Caf）的无Na^+溶液，阻断Na^+/Ca^<2+>交换器和SR，在fcs处理组灌注时，[Ca^<2+>]_i的稳态水平较低（338<正负>30 vs. 806<正负>129 nM,p<0.05, n=4）。当维拉帕米（1 mM）灌注后，这些差异减弱（294<正负>33 vs 282<正负>35 nM，NS）。用1 mM钒酸盐（作为肌层Ca^<2+>- atp酶抑制剂）预处理后灌注ONa+Caf也显示出类似的结果。另一方面，维拉帕米预处理使fcs处理组与对照组在ONa+Caf灌注时稳态[Ca^<2+>]_i无显著差异。这些数据表明，在我们的体外模型中，Ca^<2+>处理的改变与细胞肥大一起发生。Ca^<2+>处理的这些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