Tokutomi N, Tokutomi Y, Fukunaga K, Miyamoto E, Nishi K
Department of Pharmacology, Kumamoto University School of Medicine, Japan.
Brain Res. 1994 Sep 19;657(1-2):202-6. doi: 10.1016/0006-8993(94)90968-7.
Effects of bradykinin (BK) on the membrane conductance and level of cytoplasmic free Ca2+ in undifferentiated and differentiated neuroblastoma-glioma hybrid (NG108-15) cells were studied using the nystatin-perforated patch-clamp technique and fura-2 fluorometry. Under voltage clamp at -20 mV, undifferentiated cells responded to BK at > 10(-9) M, producing a biphasic current composed of an apamin-sensitive Ca(2+)-activated K+ outward current and non-specific cationic inward current. Both current components corresponding to a biphasic elevation of [Ca2+]i were completely prevented by an intracellular perfusion with EGTA (1 mM) under conventional whole cell recording condition. Undifferentiated cells revealed almost no voltage sensitive Ca2+ current. In NG108-15 cells differentiated with 8-Br-cyclic AMP (1 mM) or rolipram (1 mM), an inhibitor of type IV phosphodiesterase, BK concentration required for the non-specific cationic current with amplitude of > 100 pA was much greater than that of undifferentiated cells. This suggests that the differentiated cells decreased BK-sensitivity in induction of the non-specific cationic current. The non-specific cationic channel is suggested to play roles as a source of Ca2+ entry in undifferentiated NG108-15 cells.
采用制霉菌素穿孔膜片钳技术和fura-2荧光测定法，研究了缓激肽（BK）对未分化及分化的神经母细胞瘤-胶质瘤杂交细胞（NG108-15）膜电导和细胞质游离Ca2+水平的影响。在-20 mV电压钳制下，未分化细胞对浓度>10(-9) M的BK有反应，产生一种双相电流，该电流由蜂毒明肽敏感的Ca(2+)-激活K+外向电流和非特异性阳离子内向电流组成。在传统全细胞记录条件下，用EGTA（1 mM）进行细胞内灌注可完全阻断与[Ca2+]i双相升高相对应的两种电流成分。未分化细胞几乎没有电压敏感性Ca2+电流。在经8-溴环磷酸腺苷（1 mM）或IV型磷酸二酯酶抑制剂咯利普兰（1 mM）分化的NG108-15细胞中，产生幅度>100 pA的非特异性阳离子电流所需的BK浓度远高于未分化细胞。这表明分化细胞在诱导非特异性阳离子电流时对BK的敏感性降低。非特异性阳离子通道被认为在未分化的NG108-15细胞中作为Ca2+内流的来源发挥作用。
