Steroid-protein interactions in bovine plasma

Abstract
The binding of testosterone [T], corticosterone [B] and 17.alpha.-hydroxyprogesterone by bull plasma protein was studied by equilibrium dialysis. T in bovine plasma was bound by a CBG[corticosterone-binding globulin]-like protein and by testosterone-binding protein (TBP) of limited capacity and high affinity. The TBP was specific for C18 and C19 steroids with a 17.beta.-hydroxy group. Precision of the steroid-protein binding measurements was tested and was satisfactory. The testosterone-binding capacity in bull plasma samples did not seem to be related to T levels in peripheral plasma. Significant differences between bulls and cows with regard to the binding capacity were observed.