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.
Smirnov
A N
AN
Laboratory of Endocrinology, School of Biology, Lomonosov Moscow State University, Moscow, 119899, Russia. smirnov_an@mail.ru
Pokrovskaya
E V
EV
Levina
I S
IS
Kulikova
L E
LE
Kamernitzky
A V
AV
Shevchenko
V P
VP
D000818:Animals; D001798:Blood Proteins / Q000378:metabolism*; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D005260:Female; D007700:Kinetics; D008024:Ligands; D011374:Progesterone / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D011869:Radioligand Assay; D051381:Rats
D001798:Blood Proteins; D008024:Ligands; D011374:Progesterone