title: Metabolism and receptor binding of nandrolone and testosterone under in vitro and in vivo conditions.
abstract: The metabolism and receptor binding of nandrolone (N) and testosterone (T) were studied under in vitro and in vivo conditions. The results of both in vitro incubation studes with 3H-N and 3H-T in tissue homogenates from rats and in vivo infusion studies with 3H-N and 3H-T in conscious rats show the importance of the enzymes 5 alpha-reductase and 3 alpha/beta-hydroxysteroid-oxidoreductases in the prostate and the importance of the enzyme 17 beta-hydroxysteroid dehydrogenase in the kidney for the effects of N and T on these tissues. Following infusion of a combined dose of 3H-N and 3H-T there is a preferential retention at the receptor of 5 alpha-dihydrotestosterone (DHT) over 5 alpha-dihydronandrolone (DHN), N and T (DHT much greater than DHN greater than N greater than T) in the prostate because T is a better substrate than N for 5 alpha-reductase and because DHT binds more strongly to the androgen receptor than DHN, N and T. In the kidney 5 alpha-reductase is not important; there is a preferential retention of N in T (DHN and DHT were only present in small amounts) because N is less susceptible than T for metabolic inactivation by the enzyme 17 beta-hydroxysteroid dehydrogenase and N binds strongly to the androgen receptor. Both in vitro and in vivo studies show that N and T were relatively stable in spleen, thymus and muscular tissue (only shown in vivo) and, as a result, the same amount of N and T was bound to the receptor in these tissues in the in vivo infusion experiment.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000818:Animals; D042944:Cholestenone 5 alpha-Reductase; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D009277:Nandrolone / Q000378:metabolism*; D010088:Oxidoreductases / Q000032:analysis; D051381:Rats; D011919:Rats, Inbred Strains; D011944:Receptors, Androgen / Q000378:metabolism*; D013739:Testosterone / Q000378:metabolism*; D014316:Tritium
chemical_list: D011944:Receptors, Androgen; D014316:Tritium; D013739:Testosterone; D009277:Nandrolone; D010088:Oxidoreductases; D042944:Cholestenone 5 alpha-Reductase