An Evaluation of the Role of Prealbumin in the Binding of Thyroxine1

Abstract

The role of prealbumin in the binding of thyroxine has been investigated. Electrophoresis of human serum in agar gel with buffer solutions of barbital, borate or tris-maleate at pH 8.6, or phosphate at pH 7.4, results in a distinct separation of prealbumin from other proteins. Moreover, prealbumin is stained readily with amido black, a standard protein stain. This suggests that prealbumin is a specific fraction of the serum proteins and is not an artifact produced by certain buffer systems. Radiothyroxine, added to human serum in physiologic concentration and subjected to electrophoresis with agar gel in phosphate buffer at pH 7.4, binds to inter-alpha globulin, albumin and prealbumin. Measurements of radioactivity indicate that interalpha globulin binds approximately 46% of the radiothyroxine, albumin, 20%, and prealbumin, 30%, the remaining 4% being dispersed among the other proteins. These in vitro experiments, performed at pH 7.4 and with a physiologic concentration of hormone, favor a role for prealbumin in the binding of thyroxine.