Murata M, Fukuda K, Ishida H, Miyoshi S, Koura T, Kodama H, Nakazawa H K, Ogawa S
Department of Internal Medicine, Keio University, Tokyo, Japan.
J Mol Cell Cardiol. 1999 Jan;31(1):237-45. doi: 10.1006/jmcc.1998.0866.
This study investigates whether leukemia inhibitory factor (LIF), a potent cardiac hypertrophic cytokine, affects the L-type Ca2+ current (I(Ca,L)) and intracellular Ca2+ concentrations ([Ca2+]i) in cardiomyocytes. I(Ca,L) was recorded using a whole cell patch clamp configuration in guinea pig cardiomyocytes, and the [Ca2+]i transient was detected by use of Fluo-3 in rat cardiomyocytes. Cells were preincubated with LIF (1000 U/ml) for 15 min before whole cell recording. LIF increased I(Ca,L) by 41.8%. LIF synergistically increased I(Ca,L) with isoproterenol. Preincubation with H89 did not inhibit the LIF-induced increase in I(Ca,L), indicating that this phenomenon is PKA-independent. PD98059 completely inhibited the increase in I(Ca,L), and this effect was dose-dependent (IC50=3.6 micromol/l). Other signal transduction inhibitors including AG490, SB203580, chelerythrine, genistein, and KN62 did not affect the LIF-induced increase in I(Ca,L). Perforated patch clamp recording revealed that LIF maximally increased the I(Ca,L) by 25% at 15 min. LIF also increased the peak [Ca2+]i transient level by 63% at 15 min. PD98059 fully inhibited the increase in the [Ca2+]i transient. In conclusion, LIF increased I(Ca,L) and the [Ca2+]i transient in cardiomyocytes, and the Raf-1/MEK/ERK pathway might be involved in the modulation of this activation.
本研究调查了白血病抑制因子（LIF）这种强效的心脏肥厚细胞因子是否会影响心肌细胞中的L型钙电流（I(Ca,L)）和细胞内钙浓度（[Ca2+]i）。在豚鼠心肌细胞中采用全细胞膜片钳配置记录I(Ca,L)，并在大鼠心肌细胞中使用Fluo-3检测[Ca2+]i瞬变。在进行全细胞记录前，将细胞与LIF（1000 U/ml）预孵育15分钟。LIF使I(Ca,L)增加了41.8%。LIF与异丙肾上腺素协同增加I(Ca,L)。用H89预孵育并不抑制LIF诱导的I(Ca,L)增加，表明该现象不依赖蛋白激酶A（PKA）。PD98059完全抑制I(Ca,L)的增加，且这种作用呈剂量依赖性（半数抑制浓度[IC50]=3.6微摩尔/升）。包括AG490、SB203580、白屈菜红碱、染料木黄酮和KN62在内的其他信号转导抑制剂均不影响LIF诱导的I(Ca,L)增加。穿孔膜片钳记录显示，LIF在15分钟时使I(Ca,L)最大增加25%。LIF在15分钟时还使[Ca2+]i瞬变峰值水平增加63%。PD98059完全抑制[Ca2+]i瞬变的增加。总之，LIF增加了心肌细胞中的I(Ca,L)和[Ca2+]i瞬变，且Raf-1/丝裂原活化蛋白激酶/细胞外信号调节激酶（Raf-1/MEK/ERK）通路可能参与了这种激活的调节。
