Effect of castration on the metabolism of androgens in rat skeletal muscle.
The metabolic conversion of testosterone and 17 beta-hydroxy-5 alpha-andro-stan-3-one by cell fractions from skeletal muscle was examined. Little or no conversion of testosterone to 17 beta-hydroxy-5 alpha-androstan-3-one is observed with any skeletal muscle fraction studied. The cytosol from all muscles examined contained substantial levels of the enzyme 3 alpha-hydroxysteroid oxidoreductase, which converts 17 beta-hydroxy-5 alpha-androstan-3-one to 5 alpha-androstane-3,17 beta-diol. The Km of the reaction in the three muscles (extensor digitorum longus, soleus and levator ani) is in the order of 3-6 X 10(-6) M. Following castration, there is no significant change in the Km value of this reaction in any of the muscles. The Vmax of the conversion in the extensor digitorum longus and soleus are similar (in the order of 2.0 X 10(-11) mol/mg per min) and castration has no significant effect on Vmax in either of these muscles. Vmax is significantly lower for the levator ani (3.4 X 10(-12) mol/mg per min) than for the extensor digitorum longus and soleus. Following castration the Vmax for the levator ani undergoes a significant rise which peaks at 3 days.
D000818:Animals; D002369:Castration; D013196:Dihydrotestosterone / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D009132:Muscles / Q000033:anatomy & histology / Q000378:metabolism*; D051381:Rats; D013739:Testosterone / Q000378:metabolism*
D013196:Dihydrotestosterone; D013739:Testosterone