Influence of Various Steroids on the Specific Binding of Cortisol

Gel filtration on Sephadex columns can be used for quantitative measurement of the amount of transcortin-bound corticoids in human plasma (De Moor, Heirwegh, Heremans & Declerck-Raskin, 1962). Using this procedure the authors have studied the influence of various steroids in vitro on the cortisol-binding capacity of human plasma. Various steroids may influence the cortisol-binding capacity of human plasma in vitro. This was shown by overloading normal corticoid-poor plasma (i.e. plasma taken at 12 p.m. from a normal individual sound asleep) either with cortisol alone or with cortisol and an equal amount of another steroid. The loading dose of cortisol was always 500 mμg./ml. After 15 min. of incubation the plasmas were submitted to gel filtration and the protein-bound corticoids were determined fluorimetrically. This could be done since the other steroids tested did not fluoresce under the experimental conditions employed. The results were expressed as percentual decrease of the protein-bound fluorescence