The Binding of a Synthetic Progestin, R5020, to Transcortin and Serum Albumin

Abstract

R5020 (17,21-dimethyl-19-nor-4,9-pregnadiene-3,20-dione), a synthetic progestin, was tested for its binding to purified human transcortin, albumin and human serum. Scatchard analysis showed that R5020 bound relatively weakly to transcortin (Kass= 8×10⁶M⁻¹); in 20% human serum or albumin greater than 90%was bound with low Kass and an indeterminate number of binding sites.