Determination of the Vacant Amount of High‐Affinity Bilirubin Binding Site on Serum Albumin

Abstract

A principle for determination of the vacant amount of the high-affinity bilirubin binding site on serum albumin in the newborn is proposed. A small amount of monoacetyl-4,4''-diaminodiphenylsulfone (MADDS) is added to the serum sample and the equilibrium of binding of this substance is assessed by measuring the rate of dialysis into another volume of the same serum. MADDS is bound selectively to the specific bilirubin site. Results obtained after addition of varying amounts of 5 drugs [sodium benzoate, sodium salicylate, diphenylhydromine, ethacrynic acid, polymyxine B] and of oleate are compared with those found by the peroxidase method. Good agreement is found although certain deviations are encountered, as expected in the case of allosteric affects. Free bilirubin concentrations can be calculated from the results.