Effects of vanadate, menadione and menadione analogs on the Ca2+-activated K+ channels in human red cells. Possible relations to membrane-bound oxidoreductase activity.
The modulation of the Ca2+- (or Pb2+-)activated K+ permeability in human erythrocytes by vanadate, menadione and chloro-substituted menadione analogs was investigated by measurements of K+ fluxes and single-channel currents. Vanadate and menadione stimulate the K+ permeability by increasing the probability of channel openings; the menadione analogs, on the other hand, inhibit the K+ permeability by increasing the probability of channel closings. The compounds used in these experiments also interact with oxidoreductases; it is demonstrated that menadione analogs in contrast to menadione strongly inhibit the membrane-bound dehydrogenase in the erythrocytes. Concentrations of Pb2+ above 10 mumol/l, but not of Ca2+, inhibit the enzyme activity as well as the K+ permeability. The parallel effects on dehydrogenase activity and the K+ channels suggest a direct relationship between these two systems in the membrane of erythrocytes.
G F
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Fuhrmann
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W
Schwarz
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R
Kersten
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Sdun
D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002463:Cell Membrane Permeability / Q000187:drug effects; D004553:Electric Conductivity / Q000187:drug effects; D004910:Erythrocyte Membrane / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D007473:Ion Channels / Q000187:drug effects*; D007854:Lead / Q000494:pharmacology; D010088:Oxidoreductases / Q000097:blood*; D011188:Potassium / Q000097:blood; D012964:Sodium / Q000097:blood; D014638:Vanadates; D014639:Vanadium / Q000494:pharmacology*; D014812:Vitamin K / Q000031:analogs & derivatives / Q000494:pharmacology*
D007473:Ion Channels; D014639:Vanadium; D014812:Vitamin K; D007854:Lead; D000001:Calcimycin; D014638:Vanadates; D012964:Sodium; D010088:Oxidoreductases; D011188:Potassium; D002118:Calcium