Measurement of circulating thyroxine in several freshwater teleosts by competitive binding analysis

Abstract

A competitive binding analysis using human thyroxine-binding globulin (TBG) and Sephadex columns was the most satisfactory of several methods tested for measuring fish plasma thyroxine concentrations.Thyroxine levels were usually less than 1 μg and in most cases less than 0.5 μg per 100 ml plasma for laboratory-held brook trout and nine other freshwater species.