Cseri J
Acta Physiol Hung. 1984;64(2):143-55.
The effects of phlorizin on the action potential and voltage-dependent ionic conductances were investigated in frog (Rana esculenta) sartorius muscles. In order to study the ionic currents, phase plane trajectories of the action potentials were analysed. As a consequence of lowering the overshoot by 19%, the amplitude of the action potential was decreased on the effect of phlorizin applied at a concentration of 2 mmol/l. The maximum rate of rise of the action potential (V +max) was reduced on the average by 23%. The maximum rate of fall of the spike potential (V -max) was also diminished by about 25% and the repolarization was prolonged consequently. Due to phlorizin treatment the early negative after-potential was significantly lowered or was not noticeable at all. Analysing the phase plane trajectories of the action potentials the peak inward (Na) current was found to be decreased by about 16% despite the unchanged maximum Na conductance. At the Na equilibrium potential a 9.2 mV shift towards negative direction was observed. Both the peak outward (K) current and the maximum outward (K) conductance were reduced by 25 and 29%, resp. tau K, the time constant reflecting the kinetic properties of K conductance was increased by 36%. Phlorizin treatment prevented the repetitive activity induced by cevadine. The inhibiting actions of phlorizin on fast ionic currents developed also in cevadine-treated muscles. All of the effects of phlorizin were reversible. The presented data show that phlorizin, the well-known inhibitor of phosphorylase and a competitive antagonist of sugar uptake, is also capable of modifying the electrical properties of the frog skeletal muscle membrane.
研究了根皮苷对食用蛙缝匠肌动作电位和电压依赖性离子电导的影响。为了研究离子电流，分析了动作电位的相平面轨迹。在2 mmol/l浓度的根皮苷作用下，由于超射降低了19%，动作电位的幅度减小。动作电位的最大上升速率（V +max）平均降低了23%。锋电位的最大下降速率（V -max）也降低了约25%，因此复极化延长。由于根皮苷处理，早期负后电位显著降低或根本不明显。分析动作电位的相平面轨迹发现，尽管最大钠电导不变，但内向（钠）电流峰值降低了约16%。在钠平衡电位处，观察到向负方向有9.2 mV的偏移。外向（钾）电流峰值和最大外向（钾）电导分别降低了25%和29%。反映钾电导动力学特性的时间常数tau K增加了36%。根皮苷处理可防止由瑟瓦定诱导的重复活动。根皮苷对快速离子电流的抑制作用在经瑟瓦定处理的肌肉中也会出现。根皮苷的所有作用都是可逆的。所呈现的数据表明，根皮苷是一种著名的磷酸化酶抑制剂和糖摄取的竞争性拮抗剂，它也能够改变蛙骨骼肌膜的电特性。
