Binding of digitoxin to human serum albumin: influence of ionic strength and ionic medium on the digitoxin-albumin complex formation.

Abstract

Abstract: The binding of digitoxin to human serum albumin was studied under varying conditions with regard to the ionic strength and the ionic medium. At neutral pH and low ionic strength a substitution of Cl‐ by I‐ or SCN‐ was followed by an increased digitoxin‐albumin complex formation. The maximum binding affinity was obtained for Cl‐ > 0.4 mol/l, I‐ > 0.1 mol/l and SCN‐ > 0.05 mol/l. CCl3COO‐ was shown to be a powerful inhibitor of the digitoxin‐albumin interaction. At pH = 5 the binding affinity was uninfluenced by a substitution of Cl‐ by I‐ or SCN‐. Under similar conditions substantial variations of the ionic strength too, did not influence the binding affinity. The interpretation of this binding pattern was discussed with regard to a molecular mechanism for the digitoxin‐albumin interaction.