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.
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- Armstrong C. M., Cota G. Modification of sodium channel gating by lanthanum. Some effects that cannot be explained by surface charge theory. J Gen Physiol. 1990 Dec;96(6):1129–1140. doi: 10.1085/jgp.96.6.1129. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Clarkson T. W. Molecular and ionic mimicry of toxic metals. Annu Rev Pharmacol Toxicol. 1993;33:545–571. doi: 10.1146/annurev.pa.33.040193.002553. [DOI] [PubMed] [Google Scholar]
- Gilly W. F., Armstrong C. M. Divalent cations and the activation kinetics of potassium channels in squid giant axons. J Gen Physiol. 1982 Jun;79(6):965–996. doi: 10.1085/jgp.79.6.965. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Gögelein H., Pfannmüller B. The nonselective cation channel in the basolateral membrane of rat exocrine pancreas. Inhibition by 3',5-dichlorodiphenylamine-2-carboxylic acid (DCDPC) and activation by stilbene disulfonates. Pflugers Arch. 1989 Jan;413(3):287–298. doi: 10.1007/BF00583543. [DOI] [PubMed] [Google Scholar]
- Harris E. D. Copper transport: an overview. Proc Soc Exp Biol Med. 1991 Feb;196(2):130–140. doi: 10.3181/00379727-196-43171b. [DOI] [PubMed] [Google Scholar]
- Hille B., Woodhull A. M., Shapiro B. I. Negative surface charge near sodium channels of nerve: divalent ions, monovalent ions, and pH. Philos Trans R Soc Lond B Biol Sci. 1975 Jun 10;270(908):301–318. doi: 10.1098/rstb.1975.0011. [DOI] [PubMed] [Google Scholar]
- Kinraide T. B. Use of a Gouy-Chapman-Stern Model for Membrane-Surface Electrical Potential to Interpret Some Features of Mineral Rhizotoxicity. Plant Physiol. 1994 Dec;106(4):1583–1592. doi: 10.1104/pp.106.4.1583. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Kiss T., Györi J., Osipenko O. N., Maginyan S. B. Copper-induced non-selective permeability changes in intracellularly perfused snail neurons. J Appl Toxicol. 1991 Oct;11(5):349–354. doi: 10.1002/jat.2550110509. [DOI] [PubMed] [Google Scholar]
- Kiss T., Osipenko O. N. Toxic effects of heavy metals on ionic channels. Pharmacol Rev. 1994 Sep;46(3):245–267. [PubMed] [Google Scholar]
- Kourie J. I. Transient Cl- and K+ Currents during the Action Potential in Chara inflata (Effects of External Sorbitol, Cations, and Ion Channel Blockers). Plant Physiol. 1994 Oct;106(2):651–660. doi: 10.1104/pp.106.2.651. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Kumar K. S., Rowse C., Hochstein P. Copper-induced generation of superoxide in human red cell membrane. Biochem Biophys Res Commun. 1978 Jul 28;83(2):587–592. doi: 10.1016/0006-291x(78)91030-6. [DOI] [PubMed] [Google Scholar]
- Ma J. Y., Narahashi T. Differential modulation of GABAA receptor-channel complex by polyvalent cations in rat dorsal root ganglion neurons. Brain Res. 1993 Apr 2;607(1-2):222–232. doi: 10.1016/0006-8993(93)91510-y. [DOI] [PubMed] [Google Scholar]
- McKersie B. D., Stinson R. H. Effect of Dehydration on Leakage and Membrane Structure in Lotus corniculatus L. Seeds. Plant Physiol. 1980 Aug;66(2):316–320. doi: 10.1104/pp.66.2.316. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Rachlin J. W., Grosso A. The growth response of the green alga Chlorella vulgaris to combined divalent cation exposure. Arch Environ Contam Toxicol. 1993 Jan;24(1):16–20. doi: 10.1007/BF01061084. [DOI] [PubMed] [Google Scholar]
- Salama G., Abramson J. J., Pike G. K. Sulphydryl reagents trigger Ca2+ release from the sarcoplasmic reticulum of skinned rabbit psoas fibres. J Physiol. 1992 Aug;454:389–420. doi: 10.1113/jphysiol.1992.sp019270. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Weinreich D., Wonderlin W. F. Copper activates a unique inward current in molluscan neurones. J Physiol. 1987 Dec;394:429–443. doi: 10.1113/jphysiol.1987.sp016879. [DOI] [PMC free article] [PubMed] [Google Scholar]