PRELIMINARY CHARACTERIZATION OF THE 5α-DIHYDROTESTOSTERONE BINDING PROTEIN IN THE EPIDIDYMAL CYTOSOL FRACTION. IN VIVO STUDIES

in European Journal of Endocrinology
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ABSTRACT

Following the administration of [3H] testosterone to castrated rats in vivo, most of the radioactivity in the epididymal cytosol fraction was bound to macromolecules. The molecular weight of the androgen-macromolecular complexes was determined to about 90 000, and the frictional ratio (f/fo) was 1.62. The sedimentation coefficient was shown to be 4.6 S (± 0.2) and the complex was slightly retarded on a column of Sephadex G-100 (Einstein-Stokes radius 47–48 Å). On polyacrylamide gel electrophoresis it moved as a sharp zone with RF: 0.41.

Almost all the radioactivity bound to these macromolecules was identified as 5α-dihydrotestosterone (5α-DHT) (95%) and only a minor part (3–4%) as testosterone.

The receptor for 5α-DHT in the epididymal cytosol fraction was in its physico-chemical properties shown to be different from the androgenbinding proteins of the rat ventral prostate, and could not be demonstrated in non-target organs like liver and kidney. The receptor for 5α-DHT in the epididymal cytosol fraction did not form aggregates in hypotonic solutions, and was roughly of the same molecular size both at high and low salt concentrations.

 

     European Society of Endocrinology

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