Bányász T, Magyar J, Körtvély A, Szigeti G, Szigligeti P, Papp Z, Mohácsi A, Kovács L, Nánási P P
Department of Physiology, University Medical School of Debrecen, Hungary.
Naunyn Schmiedebergs Arch Pharmacol. 2001 Apr;363(4):383-90. doi: 10.1007/s002100000379.
Effects of endothelin-1 (ET-1) on the L-type calcium current (ICa) and delayed rectifier potassium current (IK) were studied in isolated canine ventricular cardiomyocytes using the whole-cell configuration of the patch-clamp technique. ET-1 (8 nM) was applied in three experimental arrangements: untreated cells, in the presence of 50 nM isoproterenol, and in the presence of 250 microM 8-bromo-cAMP. In untreated cells, ET-1 significantly decreased the peak amplitude of ICa by 32.3+/-4.8% at +5 mV (P<0.05) without changing activation or inactivation characteristics of ICa. ET-1 had no effect on the amplitude of IK, Ito (transient outward current) or IK1 (inward rectifier K current) in untreated cells; however, the time course of recovery from inactivation of Ito was significantly increased by ET-1 (from 26.5+/-4.6 ms to 59.5+/- 1.8 ms, P < 0.05). Amplitude and time course of intracellular calcium transients, recorded in voltage-clamped cells previously loaded with the fluorescent calcium indicator dye Fura-2, were not affected by ET-1. ET-1 had no effect on force of contraction in canine ventricular trabeculae. Isoproterenol increased the amplitude of ICa to 263+/-29% of control. ET-1 reduced ICa also in isoproterenol-treated cells by 17.8+/-2% (P<0.05); this inhibition was significantly less than obtained in untreated cells. IK was increased by isoproterenol to 213+/-18% of control. This effect of isoproterenol on IK was reduced by 31.8+/-4.8% if the cells were pretreated with ET-1. Similarly, in isoproterenol-treated cells ET-1 decreased IK by 16.2+/-1.5% (P<0.05). Maximal activation of protein kinase A (PKA) was achieved by application of 8-bromo-cAMP in the pipette solution. In the presence of 8-bromo-cAMP ET-1 failed to alter ICa or IK It was concluded that differences in effects of ET-1 on ICa and IK may be related to differences in cAMP sensitivity of the currents.
采用膜片钳技术的全细胞模式，在分离的犬心室肌细胞中研究了内皮素 -1（ET -1）对L型钙电流（ICa）和延迟整流钾电流（IK）的影响。ET -1（8 nM）在三种实验条件下施加：未处理的细胞、存在50 nM异丙肾上腺素的情况下以及存在250 μM 8 -溴 - cAMP的情况下。在未处理的细胞中，ET -1在 +5 mV时使ICa的峰值幅度显著降低32.3±4.8%（P<0.05），而不改变ICa的激活或失活特性。ET -1对未处理细胞中的IK、Ito（瞬时外向电流）或IK1（内向整流钾电流）的幅度没有影响；然而，ET -1使Ito从失活状态恢复的时间进程显著增加（从26.5±4.6 ms增加到59.5±1.8 ms，P < 0.05）。在预先加载荧光钙指示剂染料Fura -2的电压钳制细胞中记录的细胞内钙瞬变的幅度和时间进程不受ET -1影响。ET -1对犬心室小梁的收缩力没有影响。异丙肾上腺素使ICa的幅度增加到对照的263±29%。在异丙肾上腺素处理的细胞中，ET -1也使ICa降低17.8±2%（P<0.05）；这种抑制作用明显小于在未处理细胞中观察到的。异丙肾上腺素使IK增加到对照的213±18%。如果细胞先用ET -1预处理，异丙肾上腺素对IK的这种作用降低31.8±4.8%。同样，在异丙肾上腺素处理的细胞中，ET -1使IK降低16.2±1.5%（P<0.05）。通过在吸管溶液中施加8 -溴 - cAMP实现蛋白激酶A（PKA）的最大激活。在存在8 -溴 - cAMP的情况下，ET -1未能改变ICa或IK。得出的结论是，ET -1对ICa和IK影响的差异可能与电流对cAMP敏感性的差异有关。
