title: Effects of vanadate in cultured rat heart muscle cells. Vanadate transport, intracellular binding and vanadate-induced changes in beating and in active cation flux.
abstract: Cultured rat heart muscle cells have been used to study uptake and intracellular binding of Na483VO4 (vanadate), as well as the influence of vanadate on beating and 86Rb+ uptake of these cells. 1. Vanadate is taken up into cultured rat heart muscle cells in an energy-independent manner by a saturable transport system (Km approximately 60 microM, V approximately 200 pmol per mg protein per min at 37 degrees C). Analysis of intracellular binding of vanadate reveals a curved Scatchard plot indicating more than one binding site. Maximal binding amounts to 3 . 10(9) molecules of vanadate per cell. 2. Vanadate exerts a positive chronotropic and inotropic effect and increases automaticity. First effects can be seen at 1 . 10(-7) M Na3VO4. Concentrations higher than 1. 10(-3) M induce toxic effects (arrhythmias, fibrillation and stand-still of the cell). 3. Vanadate-induced alterations of beating is paralleled by a vanadate-induced stimulation of (86Rb+ + K+) uptake into the cells of up to 75%. Maximal stimulation is obtained at concentrations of 1 . 10(-4)--1 . 10(-3) M vanadate. The stimulation is thought to be due to an increased activity of (Na+ + K+)-ATPase, since it can be inhibited by ouabain. This result is in contrast to in vitro experiments with purified membrane preparations of (Na+ + K+)-ATPase of different organs, where an inhibition of (Na+ + K+)-ATPase by vanadate has been found. 4. The results indicate a possible role of vanadate as an endogenous regulator of active cation flux in heart tissue.
mesh_terms: D000818:Animals; D001667:Binding, Competitive; D001692:Biological Transport; D002478:Cells, Cultured; D006321:Heart / Q000187:drug effects*; D006339:Heart Rate / Q000187:drug effects*; D007700:Kinetics; D009206:Myocardium / Q000378:metabolism*; D051381:Rats; D012413:Rubidium; D014639:Vanadium / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D014639:Vanadium; D012413:Rubidium