The Effect of Cu2+ on Ion Transport Systems of the Plant Cell Plasmalemma

• Published in: Plant Physiology
• Main Authors: Demidchik, V., Sokolik, A., Yurin, V.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Oxford University Press (OUP) 1997
• Subjects: Nitella flexilis
• Online Access: http://dx.doi.org/10.1104/pp.114.4.1313; http://academic.oup.com/plphys/article-pdf/114/4/1313/37088264/plphys_v114_4_1313.pdf

Abstract Changes in plasmalemma permeability caused by excessive Cu2+ levels were examined in cells of a freshwater alga (Nitella flexilis) using a conventional microelectrode voltage-clamp technique. A rapid Cu2+-induced increase of plasmalemma conductance starting from 5 [mu]M Cu2+ was shown. Cu2+-induced plasmalemma conductance (ClGm) was nonselective and potential-independent, resembling the conductance of nonselective ionic leakage of the plasmalemma. The K+ channel conductance was shown to be unaltered by Cu2+, and a decrease in plasmalemma Cl- channel conductance at Cu2+ concentrations above 5 [mu]M was found. The depression of Cl- channels and ClGm were time-, dosage-, and Ca2+-dependent processes, revealing a great similarity in all parameters, with Ca2+ causing the preventive effect by shifting the effective Cu2+ concentrations to higher levels. This phenomenon may be explained by the same Cu2+-modified target on the plasmalemma both for ClGm and Cl- channel depression. In addition, a reversible, inhibitory effect of Cu2+ (>10 [mu]M) on the light-stimulated H+-ATPase electrogenic pump in the plasmalemma was demonstrated. This effect was Ca2+- independent, which made it possible to distinguish it from ClGm. Therefore, the Cu2+-induced dramatic alterations in plant cell plasmalemma permeability are caused mainly by nonselective conductance increases and electrogenic pump inhibition.