Calcium permeation and blocking effect in human leukaemia cells

Abstract EN

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 +).

Ca2+ permeation and blockade of MS channels were examined using pipettes containing different concentrations of Ca2 +.

In the presence of 2 mM CaCl2, 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, PCa / PK, was equal to 0.

75, as estimated at physiological Ca2+ concentrations.

Partial or full inhibition of inward Ca2 + currents through MS channels was observed at higher concentrations of external Ca2 + (10 or 20 mM).

No MS channels were activated when using a pipette containing 90 mM CaCl2.

Monovalent mechanogated currents Sud Med Lab J.

Vol (1) : 62-77 (2011) were not significantly affected by extracellular Ca2+ at concentrations within the physiological range (0-2 mM), and at some higher Ca2+ concentrations.