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| Effect of phlorizin on the action potential and voltage-dependent ionic conductancesin frog skeletal muscle. J Cseri Acta Physiol Hung 1984; 64(2):143-155 ICID: 168224 |
| IC™ Value: 5.00 |
| The effects of phlorizin on the action potential and voltage-dependentionic conductances were investigated in frog (Rana esculenta) sartorius muscles. In order to study theionic currents, phase plane trajectories of the action potentials were analysed. As a consequence oflowering the overshoot by 19%, the amplitude of the action potential was decreased on the effect of phlorizinapplied at a concentration of 2 mmol/l. The maximum rate of rise of the action potential (V +max) wasreduced on the average by 23%. The maximum rate of fall of the spike potential (V -max) was also diminishedby about 25% and the repolarization was prolonged consequently. Due to phlorizin treatment the earlynegative after-potential was significantly lowered or was not noticeable at all. Analysing the phaseplane trajectories of the action potentials the peak inward (Na) current was found to be decreased byabout 16% despite the unchanged maximum Na conductance. At the Na equilibrium potential a 9.2 mV shifttowards 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 propertiesof K conductance was increased by 36%. Phlorizin treatment prevented the repetitive activity inducedby cevadine. The inhibiting actions of phlorizin on fast ionic currents developed also in cevadine-treatedmuscles. All of the effects of phlorizin were reversible. The presented data show that phlorizin, thewell-known inhibitor of phosphorylase and a competitive antagonist of sugar uptake, is also capable ofmodifying the electrical properties of the frog skeletal muscle membrane. |
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ICID 168224 PMID 6333779 - click here to show this article in PubMed database |
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