Title: Poorly selective cation channels in apical membranes of epithelia
Authors: Van Driessche, Willy ×
Desmedt, L
De Smet, P
Simaels, Jeannine #
Issue Date: 1993
Series Title: EXS vol:66 pages:225-45
Abstract: The apical membrane of frog skin contains two types of pathways which allow the passage of several monovalent cations in the absence of external Ca2+. Differences between the two pathways concern their open-close kinetics, selectivity, and the affinity for several blocking agents. Type S channels open and close relatively slowly, whereas type F channels display fast open-close kinetics. Both channel types allow the passage of Na+, K+, and Rb+ currents which are blocked by divalent cations and La3+ added to the extracellular side. Type F channels are permeable for Cs+ which is, however, excluded from type S channels. Shifts in open-close kinetics induced by Mg2+ occur at concentrations below 5 microM for type F channels, whereas more than a tenfold higher dose is required for the type S pathway. UO2(2+) concentrations up to 100 microM only occlude type S channels while 100 microM tetracaine selectively blocks type F channels. Apical membranes of toad urinary bladder, cultured amphibian renal epithelia (A6), and toad colon contain only type F channels. In toad bladder and A6 cells volume expansion strongly activates this pathway. Macroscopic currents carried by Ba2+ and Ca2+ could be recorded after activation of toad bladders with oxytocin and treatment of the apical surface with nanomolar concentrations of Ag+, which seems to interact with a site located at the channel interior.
ISSN: 1023-294X
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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