Takai A, Tokuno H, Tomita T
J Physiol. 1985 May;362:39-50. doi: 10.1113/jphysiol.1985.sp015661.
In the glycogen-depleted smooth muscle of the guinea-pig taenia coli, application of glucose or beta-hydroxybutyrate (beta-HB) in the presence of 20 mM-K or carbachol (5 microM) produced a transient hyperpolarization for about 1 min followed by a sustained depolarization accompanied by spike activity. The early hyperpolarization was highly temperature dependent, so that below 30 degrees C, substrate application produced the depolarization with a delay of approximately 2 min, without a clear preceding hyperpolarization. The responses to substrate were not affected by ouabain (10 microM). Readmission of K after a treatment with K-free solution for 10 min caused a transient hyperpolarization only in the presence of substrate. This hyperpolarization was abolished by ouabain. Verapamil (0.1 microM) blocked the substrate-induced depolarization, revealing an underlying slow hyperpolarization. Removal of Ca abolished both the hyperpolarization and depolarization caused by substrate application, but the hyperpolarization disappeared much more slowly than the depolarization. Removal of the external K had little effect on the substrate-induced hyperpolarization, but the hyperpolarization induced by substrate application was increased when the external K was increased up to approximately 20 mM. Both the hyperpolarization and the depolarization were not clearly affected by completely replacing Na with choline. The results suggest that ATP supplied by the addition of substrate activates some electrogenic pump, probably a Ca pump, causing hyperpolarization, and that ATP also removes the inactivation of Ca conductance with some delay, resulting in an increased depolarization.
在豚鼠结肠带平滑肌糖原耗尽的情况下，在20 mM钾或卡巴胆碱（5 microM）存在时施加葡萄糖或β-羟基丁酸酯（β-HB）会产生约1分钟的短暂超极化，随后是持续去极化并伴有锋电位活动。早期超极化高度依赖温度，因此在30℃以下，施加底物会延迟约2分钟产生去极化，且没有明显的前期超极化。对底物的反应不受哇巴因（10 microM）影响。用无钾溶液处理10分钟后重新加入钾，仅在有底物存在时会引起短暂超极化。这种超极化被哇巴因消除。维拉帕米（0.1 microM）阻断了底物诱导的去极化，揭示出潜在的缓慢超极化。去除钙会消除由施加底物引起的超极化和去极化，但超极化消失的速度比去极化慢得多。去除细胞外钾对底物诱导的超极化影响不大，但当细胞外钾增加到约20 mM时，施加底物诱导的超极化会增强。完全用胆碱替代钠对超极化和去极化均无明显影响。结果表明，添加底物提供的ATP激活了某种生电泵，可能是钙泵，导致超极化，并且ATP还会延迟消除钙电导的失活，从而导致去极化增强。
