Cell potentials, cell resistance, and proton fluxes in corn root tissue: Effects of dithioerythritol

Studies were made of the effect of dithioerythritol on net proton flux, potassium influx and efflux, cell potential, and cell resistance in fresh and washed corn (Zea mays L. WF9XM14) root tissue. Dithioerythritol induces equal proton influx and potassium efflux rates, decreases membrane resistance, and hyperpolarizes the cell potential. Greater effects on H+ and K+ fluxes are secured at pH 7 than at pH 5. Other sulfhydryl-protecting reagents produced the same responses. No evidence could be found that dithioerythritol affected energy metabolism or membrane ATPase, and proton influx was induced in the presence of uncoupling agents. We deduce that dithioerythritol activates a passive H+/K+ antiport, driven in these experiments by the outwardly directed electrochemical gradient of K+. The net effect on H+ and K+ fluxes is believed to reside with the combined activity of a polarized H+/K+ exchanging ATPase and the passive H+/K+ antiport. A model is presented to show how the combined system might produce stable potential differences and K+ content.