Nuclear testosterone receptors in the ovine testis

Area of Science:

• Reproductive Biology
• Endocrinology
• Molecular Biology

Background:

• Nuclear androgen receptors play a crucial role in mediating the effects of androgens in the testis.
• Understanding the characteristics of these receptors is essential for comprehending male reproductive function.

Purpose of the Study:

• To characterize nuclear testosterone-receptor complexes in ram testes.
• To determine the binding properties and steroid affinities of nuclear androgen receptors.

Main Methods:

• In vitro direct labeling of hypophysectomized ram testis with [3H]testosterone.
• Extraction of nuclear receptors using 0.4 M KC1 or NaSCN.
• Agar gel electrophoresis to assess receptor migration.
• Testosterone exchange assay on intact lamb testis using [3H]testosterone.

Main Results:

• Nuclear testosterone-receptor complexes were demonstrated, with maximal binding at 45 minutes.
• Receptors were extractable and migrated anodically.
• Binding capacity was 40-180 fmoles/mg DNA with a Kd of 2 x 10(-9) M.
• Steroid affinity order: dihydrotestosterone > testosterone > estradiol > progesterone > 5 alpha-androstanediol > cyproterone > R5020.

Conclusions:

• Nuclear androgen receptors in ram testes exhibit specific binding characteristics for testosterone.
• Dihydrotestosterone demonstrates the highest affinity for these receptors, suggesting its importance in androgen action.