Ion-selective channels in K562 cells: a patch-clamp analysis.
Four types of ion-selective channels were found by the patch-clamp technique in the human erythroleukemia K562 cells. I) in cell-attached configuration at potentials less negative than -40 mV an 8 ps channel was detected. The potential dependence of channel activity suggests that this is the TTX-sensitive Na+ channel. II) A cation-selective channel was observed with equal permeability for Na+ and K+ and a potential-independent single-channel conductance of 19 pS. The channel is activated by intracellular Ca2+ and inhibited by TEA, III) A predominantly anion-selective channel was identified with the selectivity sequence NO3- > J- > Cl- = Br- >> SO4(2-). The single-channel conductance shows outward rectification, and is in symmetrical NaCl solution 19 pS at -60 mV and 54pS at +50 mV. The open- and closed-time distributions suggest one open and at least four closed states. At submicromolar concentrations, the open state is blocked by H2DIDS leading to channel flicker between open and blocked channel; higher concentrations (apparent KI = 6.8 uM) lead to a longer-lasting blocked state. Both components of inhibition are reversible. IV) In addition, an 8 pS, Na(+)- and K(+)- selective channel could be induced by application of palytoxin. For channel activity, the presence of extracellular Na+ is essential. It is assumed that the Na+, K(+)-pump molecule is involved in the channel formation. Similarly, it is discussed whether the anion-selective channel represents a pore conformation of an electrically silent anion exchanger.
Rettinger
J
J
Max-Planck-Institut für Biophysik, Frankfurt/Main, Germany.
Schwarz
W
W
D000178:Acrylamides / Q000633:toxicity; D001965:Bromides / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism; D003064:Cnidarian Venoms / Q000633:toxicity; D006801:Humans; D007454:Iodides / Q000378:metabolism; D015640:Ion Channel Gating; D004915:Leukemia, Erythroblastic, Acute / Q000473:pathology; D009566:Nitrates / Q000378:metabolism; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D015222:Sodium Channels / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism / Q000502:physiology; D013431:Sulfates / Q000378:metabolism; D014407:Tumor Cells, Cultured; D000095702:Polyether Toxins
D000178:Acrylamides; D001965:Bromides; D002118:Calcium; D002712:Chlorides; D003064:Cnidarian Venoms; D007454:Iodides; D009566:Nitrates; D011188:Potassium; D012964:Sodium; D015222:Sodium Channels; D000254:Sodium-Potassium-Exchanging ATPase; D013431:Sulfates; C010272:palytoxin; D000095702:Polyether Toxins