COMPARISON BETWEEN THE BINDING OF 19-NORTESTOSTERONE, 5α-DIHYDROTESTOSTERONE AND TESTOSTERONE IN RAT PROSTATE AND BULBOCAVERNOSUS/LEVATOR ANI MUSCLE

in Journal of Endocrinology
Authors:
M. KRIEG
Search for other papers by M. KRIEG in
Current site
Google Scholar
PubMed
Close
,
M. DENNIS
Search for other papers by M. DENNIS in
Current site
Google Scholar
PubMed
Close
, and
K. D. VOIGT
Search for other papers by K. D. VOIGT in
Current site
Google Scholar
PubMed
Close
Restricted access
Rent on DeepDyve

Sign up for journal news

SUMMARY

Specific binding of [3H]19-nortestosterone in the 100000 g cytosol of the rat bulbocavernosus/levator ani muscle (BCLA) and prostate was demonstrated by agargel electrophoresis at low temperature and compared qualitatively and quantitatively with the binding of tritiated testosterone and 5α-dihydrotestosterone (5α-DHT). Both tissues showed a greater binding affinity for 5α-DHT than for 19-nortestosterone, with testosterone binding the least well of the three. The relative binding affinities in the BCLA and prostate were: 19-nortestosterone: testosterone = 1·4, 19-nortestosterone: 5α-DHT = 0·7. The differences were statistically significant (P < 0·02). The concentrations of receptor sites for 5α-DHT were 171 ± 20 (s.d.) fmol/mg prostatic cytosol protein and 24 ± 4 (s.d.) fmol/mg BCLA cytosol protein. The in-vitro metabolism of the three steroids in both tissues was also investigated by thin-layer chromatography. After incubating for 2 h at 0 °C the prostate was shown to reduce 26% of the 5α-DHT to androstanediols whilst the BCLA showed a 5% conversion. Testosterone was converted by the prostate to 5α-DHT (10%) and the androstanediols (6%) whilst the BCLA showed little activity in this respect. Comparing these in-vitro data with in-vivo findings from the literature, in both organs there is a positive correlation of the extent of binding in vitro to the stimulation of growth in vivo, bearing in mind that testosterone is metabolized to 5α-DHT in the prostate whilst in the BCLA, 5α-reductase is essentially absent.

 

  • Collapse
  • Expand