Vanadate-induced movements of Ca2+ and K+ in human red blood cells.
Fresh human red blood cells become highly labeled with 45Ca2+ when exposed to 0.5 mM vanadate. The effect of vanadate requires its penetration into the cell, and is attributed to the inhibition of the outwardly directed Ca2+-pumping ATPase which would otherwise "mask" the uptake of 45Ca2+. Since the inhibition of the CA2+ pump by vanadate is not complete, a transmembrane Ca2+-Ca2+ exchange can be detected. The influx leg of the exchange is inhibited by verapamil, quinidine, and Co2+. This, as well as additional (kinetic) evidence, indicates that the influx of Ca2+ is a carrier-mediated process. Experiments in which the transmembrane K+ gradient has been abolished or decreased with ionophores, or by increasing the K+ concentration in the medium, suggest that the K+ gradient may play a role in the influx of Ca2+. The vanadate-induced accumulation of Ca2+ by red cells promotes a massive efflux of K+, indicating the activation of a Ca2+-sensitive K+-channel. The results indicate the occurrence of a slow cycling of Ca2+ across the red cell membrane. The influx leg of the cycle occurs through a verapamil-sensitive channel, and is possibly driven by the discharge of the transmembrane K+ gradient. The efflux leg of the cycle consists of the Ca2+-pumping ATPase.
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D001693:Biological Transport, Active / Q000187:drug effects; D002118:Calcium / Q000097:blood* / Q000494:pharmacology; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D003035:Cobalt / Q000494:pharmacology; D004912:Erythrocytes / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D007811:Lanthanum / Q000494:pharmacology; D011188:Potassium / Q000097:blood*; D014638:Vanadates; D014639:Vanadium / Q000494:pharmacology*
D014639:Vanadium; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D003035:Cobalt; D014638:Vanadates; D007811:Lanthanum; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D011188:Potassium; D002118:Calcium