16alpha,17alpha-cycloalkane derivatives of progesterone intensively bind to a rat serum protein.


The interaction of 6alpha-methyl-[1,2-3H]16alpha,17alpha-cyclohexanoprogesterone with rat serum proteins has been studied. Specific binding of this ligand characterized by Kd = 0.36 +/- 0.10 microM and concentration of binding sites (Bmax) of about 1 microM (27.8 +/- 12.5 pmol/mg total protein) was found. According to competitive analysis, the affinity of the studied progestins to a protein that differs from transcortin was to some extent correlated with their hydrophobicity. The dissociation kinetics of 3H-ligand-protein complexes were biphasic, the binding sites forming stable and labile complexes with 3H-ligand being eluted in the same region during ion-exchange chromatography. In overall properties, the serum protein differs from the progesterone receptor and the pregna-D'-pentarane-specific protein from rat uterus. It is suggested that the revealed protein may provide high progestagenic activity of 6alpha-methyl-16alpha,17alpha-cyclohexanoprogesterone by prolonging its retention in the bloodstream.

Cite this paper

@article{Smirnov200116alpha17alphacycloalkaneDO, title={16alpha,17alpha-cycloalkane derivatives of progesterone intensively bind to a rat serum protein.}, author={Alexander N. Smirnov and Elena V Pokrovskaya and Inna S. Levina and Lidya E Kulikova and Alexey V Kamernitzky and Vladimir P. Shevchenko}, journal={Biochemistry. Biokhimii︠a︡}, year={2001}, volume={66 6}, pages={688-92} }