Ohya Y, Terada K, Yamaguchi K, Inoue R, Okabe K, Kitamura K, Hirata M, Kuriyama H
Department of Pharmacology, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
Pflugers Arch. 1988 Sep;412(4):382-9. doi: 10.1007/BF01907556.
The effects of intracellular perfusion of inositol 1,4,5-trisphosphate (InsP3) or inositol 1,3,4,5-tetrakisphosphate (InsP4) on electrical responses of smooth muscle cell membranes of the rabbit portal vein were studied using the whole cell voltage clamp technique. Depolarisation to 0 mV from a holding potential of -60 mV, evoked inward Ca (Ica), transient outward (ISO), oscillatory outward (IOO) and sustained outward (ISO) currents. Generation of IOO was dependent on the [Ca]o, but it was also generated in 0 mM Ca solution for over 10 min. From amplitude histograms, IOO was divided into two components. Reduction in [Ca]o inhibited the appearance of but not the amplitudes of both IOO components. However, the larger component of IOO was more resistant to a reduction in [Ca]o than the smaller one. InsP3 (10 microM) increased the frequency of both IOO components to a greater extent than their amplitude, but the larger component was more sensitive to InsP3 than the smaller one. The increase in the occurrence of IOO induced by InsP3 did not occur following pretreatment with 3 mM caffeine or 1 nM A23187. In normal PSS, InsP3 was evoked by a depolarising pulse positive to -40 mV, whereas following perfusion with InsP3 (10 microM), IOO was evoked at -60 mV. In normal PSS, intracellular perfusion with 10 microM InsP4 changed neither the frequency nor the amplitude of IOO, and the amplitudes of ICa, ITO and ISO were also unchanged. However, in 10 mM Ca solution, 10 microM InsP4 generated IOO at a membrane potential of -60 mV.(ABSTRACT TRUNCATED AT 250 WORDS)
采用全细胞电压钳技术研究了细胞内灌注肌醇1,4,5 -三磷酸（InsP3）或肌醇1,3,4,5 -四磷酸（InsP4）对兔门静脉平滑肌细胞膜电反应的影响。从 -60 mV的钳制电位去极化至0 mV，可诱发内向钙电流（Ica）、瞬时外向电流（ISO）、振荡外向电流（IOO）和持续外向电流（ISO）。IOO的产生依赖于细胞外钙浓度（[Ca]o），但在0 mM钙溶液中超过10分钟也可产生。从幅度直方图来看，IOO可分为两个成分。降低[Ca]o可抑制两个IOO成分的出现，但不影响其幅度。然而，IOO较大的成分比较小的成分对[Ca]o降低更具抗性。10 μM的InsP3使两个IOO成分的频率增加幅度大于幅度增加幅度，且较大成分比较小成分对InsP3更敏感。用3 mM咖啡因或1 nM A23187预处理后，InsP3诱导的IOO发生率增加未出现。在正常的生理盐溶液（PSS）中，去极化脉冲正向至 -40 mV时诱发InsP3，而灌注10 μM InsP3后，在 -60 mV时诱发IOO。在正常PSS中，细胞内灌注10 μM InsP4既不改变IOO的频率也不改变其幅度，ICa、ITO和ISO的幅度也未改变。然而，在10 mM钙溶液中，10 μM InsP4在 -60 mV的膜电位下产生IOO。（摘要截短至250字）
