Partial characterization of [3H]methyltrienolone binding in rat prostate cytosol

Area of Science:

• Biochemistry
• Molecular Biology
• Endocrinology

Background:

• Prostate cytosol contains androgen receptors.
• Steroid hormone binding is crucial for understanding prostate function and disease.

Purpose of the Study:

• To characterize the binding of 3H-labelled R 1881 (methyltrienolone) to rat prostate cytosol receptors.
• To compare the properties of the R 1881-receptor complex with the 5alpha-dihydrotestosterone-receptor complex.

Main Methods:

• Radioligand binding assays using 3H-labelled R 1881.
• Inhibition studies with various steroids and anti-androgens.
• Biophysical characterization including gel filtration (Sephadex G-200), sucrose density gradient centrifugation, ion-exchange chromatography (DEAE-cellulose), and ammonium sulfate precipitation.
• DNA-cellulose chromatography.

Main Results:

• 3H-labelled R 1881 exhibited high affinity (Kd = 2 x 10(-9) M) and low capacity (11-15 fmol/mg protein) binding in rat prostate cytosol.
• Binding was inhibited by androgens (5alpha-dihydrotestosterone, testosterone) and anti-androgens (cyproterone acetate, LEO 1727), but not by other steroids.
• The R 1881-receptor complex displayed characteristics consistent with an androgen receptor, including sedimentation coefficient (3.5 S) and DNA-binding properties (20% retained by DNA-cellulose).

Conclusions:

• The 3H-labelled R 1881-receptor complex in rat prostate cytosol shares significant similarities with the 5alpha-[3H]dihydrotestosterone-receptor complex.
• These findings support the use of R 1881 as a ligand for studying androgen receptors in the rat prostate.