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Mechanosensitive cation channels in human leukaemia cells: calcium permeation and blocking effect
Author(s) -
Staruschenko Alexandr V.,
Vedernikova Elena A.
Publication year - 2002
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2001.015222
Subject(s) - chemistry , mechanosensitive channels , biophysics , pipette , conductance , permeation , ion channel , calcium , membrane potential , patch clamp , membrane , calcium activated potassium channel , sodium , analytical chemistry (journal) , chromatography , biochemistry , receptor , mathematics , organic chemistry , biology , combinatorics
Cell‐attached and inside‐out patch‐clamp methods were employed to identify and characterize mechanosensitive (MS) ionic channels in the plasma membrane of human myeloid leukaemia K562 cells. A reversible activation of gadolinium‐blockable mechanogated currents in response to negative pressure application was found in 58 % of stable patches ( n = 317 ). I ‐ V relationships measured with a sodium‐containing pipette solution showed slight inward rectification. Data analysis revealed the presence of two different populations of channels that were distinguishable by their conductance properties (17.2 ± 0.3 pS and 24.5 ± 0.5 pS), but were indistinguishable with regard to their selective and pharmacological properties. Ion‐substitution experiments indicated that MS channels in leukaemia cells were permeable to cations but not to anions and do not discriminate between Na + and K + . The channels were fully impermeable to large organic cations such as Tris + and N ‐methyl‐ d ‐glucamine ions (NMDG + ). Ca 2+ permeation and blockade of MS channels were examined using pipettes containing different concentrations of Ca 2+ . In the presence of 2 m m CaCl 2 , when other cations were impermeant, both outward and inward single‐channel currents were observed; the I ‐ V relationship showed a unitary conductance of 7.7 ± 1.0 pS. The relative permeability value, P Ca / P K , was equal to 0.75, as estimated at physiological Ca 2+ concentrations. Partial or full inhibition of inward Ca 2+ currents through MS channels was observed at higher concentrations of external Ca 2+ (10 or 20 m m ). No MS channels were activated when using a pipette containing 90 m m CaCl 2 . Monovalent mechanogated currents were not significantly affected by extracellular Ca 2+ at concentrations within the physiological range (0‐2 m m ), and at some higher Ca 2+ concentrations.