title: The non-selective voltage-activated cation channel in the human red blood cell membrane: reconciliation between two conflicting reports and further characterisation.
abstract: Using the patch-clamp technique, the non-selective, voltage-activated cation channel in the human red blood cell (RBC) membrane was further characterised. Activity of the cation channel could be demonstrated at a range of salt concentrations with the current-voltage characteristics for monovalent cations going from linear to superlinear functions, depending on the cation concentration in the range of 100-500 mM. The non-selective voltage-activated cation channel was demonstrated to be permeable to the divalent cations Ca2+ and Ba2+, and even Mg2+. The current-voltage relations for the divalent cations were superlinear even at 75 mM salt concentration, but indicated outward rectification in contrast to the I-V curve for monovalent cations. The degree of activation at a given membrane potential depended strongly on the prehistory of the channel. The gating exhibited hysteretic-like behaviour, since the quasi steady-state deactivation and activation curves were displaced by approximately 25 mV. This result fully explains apparent discrepancies between V0.5-values previously obtained by slightly different experimental protocols. The possible physiological/pathophysiological role of the channel is discussed in the context of the demonstrated permeability for divalent cations.
authors: Biophysics Section, Institute of Biology, Humboldt University Berlin, Germany.
authors: L
authors: L
authors: Kaestner
authors: P
authors: P
authors: Christophersen
authors: I
authors: I
authors: Bernhardt
authors: P
authors: P
authors: Bennekou
mesh_terms: D004910:Erythrocyte Membrane / Q000502:physiology*; D006801:Humans; D015640:Ion Channel Gating; D007473:Ion Channels / Q000502:physiology*; D018408:Patch-Clamp Techniques
chemical_list: D007473:Ion Channels