Protein Bound Bromine in Blood Serum

Abstract

By a tracer study, using ⁸²Br, it is demonstrated that bromine is bound to serum proteins in vivo. ⁸²Br⁻ of high specific activity was injected into rabbits and serum removed one day later. Approximately ½% of the total ⁸²Br in the serum was found to be protein-bound at this stage. The application of various separation methods (electrophoresis, bromide exchange, denaturation followed by desalting) showed that one-third of the protein-bound bromine is loosely attached whereas two-thirds are firmly bound. After partial and complete enzymatic hydrolysis the bromine was found in the amino acid fraction. On the basis of the elution pattern of the amino acids on calibrated cation exchange resin columns it is concluded that the main portion of the radioactivity appeared to be associated with 3-bromo-L-tyrosine. Little, if any, bromine was observed in the serum lipids and in the thyroxine fraction isolated from serum proteins.