Inhibition of electrogenesis by aluminum in characean cells

The effects of aluminum (Al) on electrogenesis at the plasma membrane were examined in internodal cells of Chara corallina. After treating cells with 0.1 mM AlCl3 (pH 4.5), we measured both the membrane potential and the membrane resistance in artificial pond water (pH 5.6). Electrogenesis at the membrane was significantly inhibited by the treatment with AlCl3. A decrease in the pump current of the electrogenic proton pump and/or a decrease in the electrical resistance (an increase in conductance) of the passive diffusion channel were considered to be responsible for the inhibition of electrogenesis. CaCl2 had a partial ameliorating effect. Both malic acid and citric acid were very effective in reversing the effects of AlCl3. In addition, these organic acids restored electrogenesis in cells that had been treated with AlCl3. It is suggested that Al affects electrogenesis from the exterior of the membrane, at least during the initial stages of treatment (4-24 h).