Li Shi-Ying, Huang Bin-Bin, Ouyang Shou
Xiamen Institute of Medicine, 2 Tongan Road, Xiamen 361003, Fujian Province, China.
World J Gastroenterol. 2006 Jan 21;12(3):420-5. doi: 10.3748/wjg.v12.i3.420.
To investigate the action of genistein (GST), a broad spectrum tyrosine kinase inhibitor, on voltage-gated potassium channels in guinea pig proximal colon smooth muscle cells.
Smooth muscle cells in guinea pig proximal colon were enzymatically isolated. Nystatin-perforated whole cell patch clamp technique was used to record potassium currents including fast transient outward current (IKto) and delayed rectifier current (IKdr), two of which were isolated pharmacologically with 10 mmol/L tetraethylammonium or 5 mmol/L 4-aminopyridine. Contamination of calcium-dependent potassium currents was minimized with no calcium and 0.2 mmol/L CdCl2 in an external solution.
GST (10-100 micromol/L) reversibly and dose-dependently reduced the peak amplitude of IKto with an IC50 value of 22.0+/-6.9 micromol/L. To a lesser extent, IKdr was also inhibited in both peak current and sustained current. GST could not totally block the outward potassium current as a fraction of the outward potassium current, which was insensitive to GST. GST had no effect on the steady-state activation (n=6) and inactivation kinetics (n=6) of IKto. Sodium orthovanadate (1 mmol/L), a potent inhibitor of tyrosine phosphatase, significantly inhibited GST-induced inhibition (P<0.05).
GST can dose-dependently and reversibly block voltage-gated potassium channels in guinea pig proximal colon smooth muscle cells.
研究广谱酪氨酸激酶抑制剂染料木黄酮（GST）对豚鼠近端结肠平滑肌细胞电压门控钾通道的作用。
酶法分离豚鼠近端结肠平滑肌细胞。采用制霉菌素穿孔全细胞膜片钳技术记录钾电流，包括快速瞬时外向电流（IKto）和延迟整流电流（IKdr），其中两种电流分别用10 mmol/L四乙铵或5 mmol/L 4-氨基吡啶进行药理学分离。通过在外部溶液中无钙和添加0.2 mmol/L氯化镉，将钙依赖性钾电流的污染降至最低。
GST（10 - 100 μmol/L）可逆且剂量依赖性地降低IKto的峰值幅度，IC50值为22.0±6.9 μmol/L。在较小程度上，IKdr的峰值电流和持续电流也受到抑制。GST不能完全阻断外向钾电流，因为存在一部分对外向钾电流不敏感的GST。GST对IKto的稳态激活（n = 6）和失活动力学（n = 6）没有影响。酪氨酸磷酸酶的强效抑制剂原钒酸钠（1 mmol/L）显著抑制GST诱导的抑制作用（P < 0.05）。
GST可剂量依赖性且可逆地阻断豚鼠近端结肠平滑肌细胞的电压门控钾通道。
