Papp Z, Van Der Velden J, Borbély A, Edes I, Stienen G J M
UDMHSC, Division of Clinical Physiology, Institute of Cardiology, Debrecen, Hungary.
J Muscle Res Cell Motil. 2004;25(3):219-24. doi: 10.1023/b:jure.0000038365.74532.75.
During heart failure, alterations occur in contractile protein expression and phosphorylation, which may influence the effects of Ca2+ -sensitizers. To quantify the magnitude of these effects, isometric force was studied in mechanically isolated Triton-skinned myocytes from end-stage failing and non-failing donor hearts under control conditions (pH 7.2; no added inorganic phosphate (Pi)) and under mimicked ischemic conditions (pH 6.5; 10 mM Pi). Two different Ca2+ -sensitizers were used: EMD 53998 (10 microM), which exerts its influence through the actin-myosin interaction, and OR-1896 (10 microM) (the active metabolite of levosimendan), which affects the Ca2+ -sensory function of the thin filaments. The maximal force (Po) measured at saturating Ca2+ concentration and the resting force (Prest) determined in the virtual absence of Ca2+ (pCa 9) did not differ between the failing and non-failing myocytes, but the Ca2+ concentration required to induce the half-maximal force under control conditions was significantly lower in the failing than in the non-failing myocytes (DeltapCa50=0.15). This difference in Ca2+ -sensitivity, however, was abolished during mimicked ischemia. EMD 53998 increased Po and Prest by approximately 15% of Po and greatly enhanced the Ca2+ -sensitivity (DeltapCa50 > 0.25) of force production. OR-1896 did not affect Po and Prest, and provoked a small, but significant Ca2+ -sensitization (DeltapCa50 approximately 0.1). All of these effects were comparable in the donor and failing myocytes, but, in contrast with OR-1896, EMD 53998 considerably diminished the difference in the Ca2+ -sensitivities between the failing and non-failing myocytes. The action of Ca2+ -sensitizers under mimicked ischemic conditions was impaired to a similar degree in the donor and the failing myocytes. Our results indicate that the Ca2+ -activation of the myofibrillar system is altered in end-stage human heart failure. This modulates the effects of Ca2+ -sensitizers both under control and under mimicked ischemic conditions.
在心力衰竭期间，收缩蛋白的表达和磷酸化会发生改变，这可能会影响Ca2+敏化剂的作用。为了量化这些作用的程度，我们在对照条件（pH 7.2；不添加无机磷酸盐（Pi））和模拟缺血条件（pH 6.5；10 mM Pi）下，对来自终末期衰竭和非衰竭供体心脏的机械分离的经曲拉通处理的心肌细胞的等长力进行了研究。使用了两种不同的Ca2+敏化剂：EMD 53998（10 microM），它通过肌动蛋白-肌球蛋白相互作用发挥作用；OR-1896（10 microM）（左西孟旦的活性代谢物），它影响细肌丝的Ca2+传感功能。在饱和Ca2+浓度下测得的最大力（Po）和在几乎不存在Ca2+（pCa 9）的情况下测定的静息力（Prest）在衰竭和非衰竭心肌细胞之间没有差异，但在对照条件下诱导半最大力所需的Ca2+浓度在衰竭心肌细胞中明显低于非衰竭心肌细胞（DeltapCa50 = 0.15）。然而，这种Ca2+敏感性的差异在模拟缺血期间消失了。EMD 53998使Po和Prest增加了约Po的15%，并大大增强了力产生的Ca2+敏感性（DeltapCa50 > 0.25）。OR-1896不影响Po和Prest，并引起了小但显著的Ca2+敏化（DeltapCa50约为0.1）。所有这些作用在供体和衰竭心肌细胞中都是可比的，但与OR-1896不同，EMD 53998大大减小了衰竭和非衰竭心肌细胞之间Ca2+敏感性的差异。在模拟缺血条件下，Ca2+敏化剂在供体和衰竭心肌细胞中的作用受损程度相似。我们的结果表明，在终末期人类心力衰竭中，肌原纤维系统的Ca2+激活发生了改变。这在对照和模拟缺血条件下均调节了Ca2+敏化剂的作用。
