Influence of Various Endogenous Factors on CBG Activity in the Rat

Abstract

Soon after the discovery of CBG in the human blood, it was observed that the plasma of the rat also contains macromolecules capable of binding cortisol with high affinity; the binding capacity was found to be higher than that of human plasma (Daughaday, 1958 a; Slaunwhite and Sandberg, 1959). Rat CBG activity, which can also be demonstrated in serum, was found to be stable at 37° for at least 72 hrs (Westphal, 1961) or 96 hrs (Westphal et al., 1962), resembling human CBG in that respect (Daughaday et al., 1959). These basic observations on a high-affinity binding system for corticosteroids in the rat, similar to transcortin in the human, made possible the general investigation of the corticosteroid-binding protein by experimental approaches, in a thoroughly studied laboratory animal (Westphal, 1961). The general characteristics of the corticosteroid-binding protein in rat serum have been discussed in Chapter VIII. 4 in connection with the properties of human CBG.