Binding properties of purified adult and fetal bovine serum albumin.

Fetal and adult bovine serum albumin were purified by standard techniques and then treated with activated charcoal at pH 2.75 to remove small molecular weight legands. The two proteins were compared and found to be identical by the following criteria: isoelectric focusing, electrophoresis on cellulose acetate and polyacrylamide gel, by the binding of bromcresol green, salicylic acid, diphenylhydantoin, and six different fatty acids (palmitic, stearic, oleic, elaidic, linoleic, and arachidonic). Reports of marked differences in the capacities of fatal and ault plasma to bind bilirubin and various drugs have usually been attributed to the presence of a "fetal" albumin. Our results, however, are consistent with the view that there is no difference between adult and fetal albumin and that the observed altered binding properties of fetal plasma are due to the tight binding of a ligand to fetal albumin in blood, which modifies the protein's affinity for lipophilic compounds.