Inhibition and acceleration of na-ca+k exchange fluxes by silver
ions in bovine retinal rod outer segments.
Schnetkamp, Paul P. M., Robert T. Szerencsei, Joseph E. Tucker, and
Peter Vandenelzen.
Department of Medical Biochemistry, University of Calgary, Health
Science Centre, 3330 Hospital Drive N.W., Calgary, Alberta, T2N 4N1,
Canada.
APStracts 2:0201C, 1995.
The effect of silver ions on Ca2+ fluxes mediated by the retinal rod
Na-Ca+K exchanger was investigated in intact bovine rod outer
segments (ROS). Nain-dependent Ca2+ influx and Naout-dependent Ca2+
efflux were monitored by changes in cytosolic free Ca2+ measured with
the fluorescent Ca2+-indicating dye fluo-3. Silver ions were the most
effective inhibitor of Na-Ca+K exchange fluxes described to date with
half-maximal inhibition observed at 2-8 [mu]M Ag+. Inhibition by
silver could be reversed by addition of [beta]-mercaptoethanol, but
not by addition of cysteine. Reversal by [beta]-mercaptoethanol
resulted in a marked acceleration of Naout-dependent lowering of
cytosolic free Ca2+, but not of Nain-dependent Ca2+ influx. We
suggest that silver ions inhibit and accelerate Na-Ca+K exchange
fluxes by binding to cysteine residues on the cytosolic surface of
the exchanger protein.
Received 9 March 1995; accepted in final form 11 May 1995.
APS Manuscript Number C134-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 26 May 1995.