Title: External Ni2+ and ENaC in A6 cells: Na+ current stimulation by competition at a binding site for amiloride and Na+
Authors: Cucu, Daniela ×
Simaels, Jeannine
Van Driessche, Willy
Zeiske, W #
Issue Date: Jul-2003
Publisher: Springer-verlag
Series Title: Journal of membrane biology vol:194 issue:1 pages:33-45
Abstract: In cultured A6 monolayers from distal Xenopus kidney, external Ni2+ stimulated active Na+ uptake via the epithelial Na+ channel, ENaC. Transepithelial capacitance measurements ruled out exocytosis of ENaC-containing vesicles underlying the Ni2+ effect. Na+ current noise analysis was performed using the neutral Na+-channel blocker 6-chloro-3.5-diamino-pyrazine-2-carboxamide (CDPC) and amiloride. The analysis of CDPC-induced noise in terms of a three-state channel model revealed that Ni2+ elicits an increase in the number of open channels as well as in the spontaneous open probability. While Ni2+ had no influence on CDPC-blocker kinetics, the macroscopic and microscopic blocking kinetics of amiloride were affected. Ni2+ turned out to compete with amiloride for a putative binding site but not with CDPC. Moreover, external Na+-known to compete with amiloride and so producing the "self-inhibition" phenomenon-and Ni2+ exerted mutually exclusive analogous effects on amiloride kinetics. Na+ current kinetics revealed that Ni2+ prevents ENaC to be downregulated by self-inhibition. Co2+ behaved similarly to Ni2+, whereas Zn2+ did not. Attempts to disclose the chemical nature of the site reacting with Ni2+ suggested cysteine but not histidine as reaction partner.
ISSN: 0022-2631
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Department of Cellular and Molecular Medicine - miscellaneous
Physiology Section (-)
× corresponding author
# (joint) last author

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