INTERACTION OF WARFARIN WITH HUMAN-SERUM ALBUMIN - A STOICHIOMETRIC DESCRIPTION

  • 1 January 1985
    • journal article
    • research article
    • Vol. 27  (2) , 263-270
Abstract
Reversible binding of warfarin [anticoagulant] to defatted [human] serum albumin was studied by equilibrium dialysis at pH 7.4, in a 66 mM sodium phosphate buffer at 37.degree.. The binding isotherm could be described by 2 stoichiometric binding constants, K1 in the range 141,000-192,000 M-1 and K2 at 39,000-57,000 M-1. At least 2 additional molecules could be bound but gave indeterminate binding constants. The product .KAPPA.3 .times. K4 was about 4.7 .times. 107 M-2. Different site models were possible, either 1 high affinity and several low affinity sites, or 2 high affinity sites, cooperative, independent or anticooperative, together with 2 low affinity sites. Binding affinity for the 1st warfarin molecule did not vary with pH in the interval from 6-9. The affinity decreased with increasing concentrations of Na2SO4, NaCl, and CaCl, depending on ionic strength. Specific effects of Cl and Ca ions were not observed. Light absorption spectra indicated that the warfarin anion was bound to albumin. All observations were consistent with a binding process involving albumin and the warfarin anion, without participation of H ions and not influenced by the N-B conformational transition of albumin.