Cheeseman JM, Lafayette PR, Gronewald JW, Hanson JB. Effect of ATPase inhibitors on cell potential and k influx in corn roots.
PLANT PHYSIOLOGY 1980;
65:1139-45. [PMID:
16661348 PMCID:
PMC440498 DOI:
10.1104/pp.65.6.1139]
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Abstract
Experiments were performed to determine the effect of plasmalemma ATPase inhibitors on cell potentials (Psi) and K(+) ((86)Rb) influx of corn root tissue over a wide range of K(+) activity. N,N'Dicyclohexylcarbodiimide (DCCD), oligomycin, and diethylstilbestrol (DES) pretreatment greatly reduced active K(+) influx and depolarized Psi at low, but not at high, K(+) activity (K degrees ). More comprehensive studies with DCCD and anoxia showed nearly complete inhibition of the active component of K(+) influx over a wide range of K degrees , with no effect on the apparent permeability constant. DCCD had no effect on the electrogenic component of the cell potential (Psi(p)) above 0.2 millimolar K degrees . Net proton efflux was rapidly reduced 80 to 90% by DCCD. Since tissue ATP content and respiration were only slightly affected by the DCCD-pretreatment, the inhibitions of active K(+) influx and Psi(p) at low K degrees can be attributed to inhibition of the plasmalemma ATPase.It is concluded that by DCCD treatment, the energy-linked electrogenic system at high K degrees is separated from the energy-linked K(+) influx system at low K degrees . The results are analyzed in terms of electrical analogue models of the membrane. The presence of two, algebraically additive electrogenic components is indicated; one is better modeled as a current source (system I) and one as a voltage source (system II). No K(+) stimulation of system II is required to produce the observed K degrees dependence of Psi(p).
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