The Journal of Membrane Biology

, Volume 89, Issue 2, pp 153–161 | Cite as

Inward membrane current inChara inflata: II. Effects of pH, Cl-channel blockers and NH 4 + , and significance for the hyperpolarized state

  • S. D. Tyerman
  • G. P. Findlay
  • G. J. Paterson


The Cl component of the voltage- and time-dependent inward current activated by hyperpolarizing the membrane ofChara inflata increases exponentially as the external pH, pH o , is lowered from 7 with the membrane potential difference (PD) kept constant. Lanthanum and anthracene-9-carboxylic acid (A-9-C, a Cl channel blocker) both blocked the Cl component and removed the pH o sensitivity of the inward current. Lanthanum, however, also decreased the K+ conductance. The hyperpolarized membrane is depolarized by A-9-C in a manner similar to that caused by the removal of external Cl. Low external concentrations of NH 4 + stimulated the Cl component of the inward current probably as a result of a change in cytoplasmic pH rather than as a result of a change in cytoplasmic [Cl], since the effect was observed in Cl-free solutions. The results show that the membrane PD, at hyperpolarized levels, is most likely determined by two factors: the proton extrusion pump, provided it has a reversal PD more negative than about −300 mV, and a voltage-dependent Cl leak.

Key Words

Cl channels Chara inflata pH channel blockers NH4+ 


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Copyright information

© Springer-Verlag 1986

Authors and Affiliations

  • S. D. Tyerman
    • 1
  • G. P. Findlay
    • 1
  • G. J. Paterson
    • 1
  1. 1.School of Biological SciencesThe Flinders University of South AustraliaBedford Park

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