title: Sodium-dependent cardiac glycoside binding: experimental evidence and hypothesis.
abstract: 1 The influence of increasing Na+ concentrations on the binding of digitoxin, digoxin and ouabain was examined in a Na+-K+-ATPase preparation of guinea-pig hearts. 2 Two distinct processes seem to be involved in this interaction: one binding process was activated at low Na+ concentrations. The maximum binding capacities were different and the K0.5 values were nearly identical for the cardiac glycosides studied. 3 In contrast, the second binding process was activated at appreciably higher Na+ concentrations, the maximum binding capacities were almost identical and the K0.5 values were different for the cardiac glycosides studied. 4 On the basis of these results attempts are made to explain the well known differences in the myocardial accumulation of cardiac glycosides.
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000818:Animals; D002301:Cardiac Glycosides / Q000378:metabolism*; D006168:Guinea Pigs; D066298:In Vitro Techniques; D009206:Myocardium / Q000378:metabolism; D011188:Potassium / Q000378:metabolism; D011485:Protein Binding; D012964:Sodium / Q000378:metabolism*; D013997:Time Factors
chemical_list: D002301:Cardiac Glycosides; D012964:Sodium; D000251:Adenosine Triphosphatases; D011188:Potassium