Changes of cytoplasmic pH in frog nerve fibers during K+‐induced membrane depolarization

FEBS Letters

Vergun, O.V.³  Valkina, O.N.¹  Khodorov, B.I.³  Turovetsky, V.B.² 

[1] Ulyanovsk State Pedagogical University, Ulyanovsk, Russian Federation;M. V. Lomonosov Moscow State University, 119899 Moscow, Russian Federation;Institute of General Pathology and Pathophysiology, Russian Academy of Medical Sciences, Baltiyskaya Str. 8, 125315 Moscow, Russia

关键词: Nerve fiber;    Intracellular pH;    Na+/H+ exchange;    Depolarization;    Tetraethylammonium;    Tetrodotoxin;    FCCP;    Sodium channel;    [Na+]i;    intracellular sodium concentrations;    [Na+]o;    external concentration of sodium;    [K+]o;    potassium;    [Ca2+]o;    calcium;    pHo;    external;    pHi;    internal (cytoplasmic) pH;    CBS;    control buffer salt solution;    TEA;    tetraethylammonium;    TTX;    tetrodotoxin;    FCCP;    carbonyl cyanide p-trifluoromethoxy phenylhydrazone;    EGTA;    ethyleneglycol bis(β-aminoethylether)-N;    N′-tetraacetic acid;    HEPES;    4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid;    FDA;    fluorescein diacetate;    N;    nerve trunk;    F;    nerve fiber bundle;   

DOI  :  10.1016/0014-5793(95)00143-W

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Frog sciatic nerve and its thin bundles were loaded with fluorescein diacetate in order to monitor changes in cytoplasmic pH (pH_i) caused by high K⁺ depolarization. Isosmotic substitution of external Na⁺ by K⁺ at pH_o 7.3 led to a steady concentration-dependent (20–120 mM K⁺) decrease in pH_i. Elevation of pH_o from 7.3 to 8.5 prevented or even reversed these pH_i changes, indicating their strong dependence on transmembrane H⁺ fluxes. The depolarization-induced intracellular acidification could not be prevented or decreased by any of the following treatments: removal of external Ca²⁺; application of the Cat²⁺ antagonists Ni²⁺ and Co²⁺; blockade of⁺ channels by TEA; addition to the external solution of Zn²⁺, a blocker of putative voltage-sensitive H⁺ channels. By contrast, blockade of Na⁺ channels by 1–3 μM TTX prevented the effect of high K⁺ concentrations on pH_i. It is concluded that the decrease in pH_i induced by a prolonged membrane depolarization in frog nerve fibers is mainly due to an enhanced H⁺ influx through non-inactivating Na⁺ channels.

【 授权许可】

Unknown