von Lewinski Dirk, Voss Kerstin, Hülsmann Swen, Kögler Harald, Pieske Burkert
Abteilung Kardiologie und Pneumologie, Georg-August-Universität Göttingen, Germany.
Circ Res. 2003 Feb 7;92(2):169-76. doi: 10.1161/01.res.0000051885.70159.12.
Myocardial generation of insulin-like growth factor-1 (IGF-1) is altered in hypertrophy and heart failure, but there are no reports on acute functional effects of IGF-1 in human cardiac muscle. We examined inotropic responses and signal transduction mechanisms of IGF-1 in human myocardium. Experiments were performed in isolated trabeculae or cardiomyocytes from 46 end-stage failing hearts. The effect of IGF-1 (0.001 to 0.2 micromol/L) on isometric twitch force (37 degrees C, 1 Hz), intracellular Ca2+ transients (aequorin method), sarcoplasmic reticulum (SR) Ca2+ content (rapid cooling contractures), L-type Ca2+ current (whole-cell voltage clamp), and cAMP concentrations was assessed. In addition, the effects of blocking IGF-1 receptors, phosphoinositide 3-kinase (PI3-kinase), protein kinase C (PKC), or transsarcolemmal Ca2+ entry were tested. IGF-1 exerted concentration-dependent positive inotropic effects (twitch force increased to maximally 133+/-4% of baseline values at 0.1 micromol/L; P<0.05). The IGF-1 receptor antibody alphaIR3 or the PI3-kinase inhibitor wortmannin prevented the functional effects. The inotropic response was paralleled by increases in Ca2+ transients and SR Ca2+ content. IGF-1 (0.1 micromol/L) increased L-type Ca2+ current amplitude by 24+/-7% (P<0.05). Blockade of SR function did not affect the inotropic response to IGF-1. In contrast, L-type Ca2+ channel blockade with diltiazem partially prevented ( approximately 50%) the inotropic response to IGF-1. Inhibition of PKC (GF109203X), Na+-H+ exchange (HOE642), or reverse-mode Na+-Ca2+ exchange (KB-R7943) reduced the response to IGF-1 by approximately 60% to 70%. IGF-1 exerts Ca2+-dependent positive inotropic effects through activation of IGF-1 receptors and a PI3-kinase-dependent pathway in failing human myocardium. The increased [Ca2+]i with IGF-1 originates from both enhanced L-type Ca2+ currents and enhanced Na+-H+ exchange-dependent reverse-mode Na+-Ca2+ exchange. These nongenomic functional effects of IGF-1 may be of clinical relevance.
胰岛素样生长因子-1（IGF-1）在心肌肥大和心力衰竭时的生成会发生改变，但关于IGF-1对人心肌的急性功能影响尚无报道。我们研究了IGF-1在人心肌中的变力反应和信号转导机制。实验在来自46例终末期衰竭心脏的离体小梁或心肌细胞中进行。评估了IGF-1（0.001至0.2微摩尔/升）对等长收缩力（37℃，1赫兹）、细胞内Ca2+瞬变（水母发光蛋白法）、肌浆网（SR）Ca2+含量（快速冷却挛缩）、L型Ca2+电流（全细胞电压钳）和cAMP浓度的影响。此外，还测试了阻断IGF-1受体、磷酸肌醇3-激酶（PI3-激酶）、蛋白激酶C（PKC）或跨肌膜Ca2+内流的效果。IGF-1发挥浓度依赖性正性变力作用（在0.1微摩尔/升时收缩力增加至基线值的最大133±4%；P<0.05）。IGF-1受体抗体αIR3或PI3-激酶抑制剂渥曼青霉素可阻止其功能作用。变力反应伴随着Ca2+瞬变和SR Ca2+含量的增加。IGF-1（0.1微摩尔/升）使L型Ca2+电流幅度增加24±7%（P<0.05）。阻断SR功能不影响对IGF-1的变力反应。相反，用硫氮䓬酮阻断L型Ca2+通道可部分阻止（约50%）对IGF-1的变力反应。抑制PKC（GF109203X）、Na+-H+交换（HOE642）或反向模式Na+-Ca2+交换（KB-R7943）可使对IGF-1的反应降低约60%至70%。在衰竭的人心肌中，IGF-1通过激活IGF-1受体和PI3-激酶依赖性途径发挥Ca2+依赖性正性变力作用。IGF-1使[Ca2+]i升高既源于增强的L型Ca2+电流，也源于增强的Na+-H+交换依赖性反向模式Na+-Ca2+交换。IGF-1的这些非基因组功能作用可能具有临床相关性。
