Inhibition of 5 alpha-reductase, receptor binding, and nuclear uptake of androgens in the prostate by a 4-methyl-4-aza-steroid.
17 beta-N,N-Diethylcarbamoyl-4-methyl-4-aza-5 alpha-androstan-3-one (DMAA) is a potent reversible inhibitor of 5 alpha-reductase. The inhibition by DMAA of the conversion of testosterone to 5 alpha-dihydrotestosterone by rat prostate 5 alpha-reductase is competitive with testosterone, the apparent Ki being 5 nM, and uncompetitive with NADPH, DMAA inhibited both membrane-bound and solubilized 5 alpha-reductase. DMAA has moderate affinity for the prostate cytosol androgen receptor: 3 X 10(-6) M gives 50% inhibition of the binding of 10(-9) M 5 alpha-[3H]dihydrotestosterone to this receptor. This affinity to the androgen receptor is 1,000-, 500-, 120-, and 40-fold lower than that of 5 alpha-dihydrotestosterone, testosterone, spironolactone, and cyproterone acetate, respectively, and 7-fold higher than that of cimetidine. After incubation of [3H]testosterone with minced prostate, more than 90% of the radioactivity extracted from the nuclei co-chromatographed with 5 alpha-dihydrotestosterone and the rest with testosterone. DMAA at low concentrations decreased the ratio of 5 alpha-dihydrotestosterone to testosterone in the nuclei without significantly reducing the total uptake. DMAA at high concentrations also reduced the total radioactivity in the nuclei. This differential effect may reflect a higher affinity of DMAA for 5 alpha-reductase than for the androgen receptor. When 5 alpha-[3H]dihydrotestosterone was used in the tissue incubations, all radioactivity extracted from nuclei co-chromatographed with 5 alpha-dihydrotestosterone, regardless of whether or not DMAA was present. This nuclear uptake of 5 alpha-dihydrotestosterone is inhibited only by high concentrations of DMAA. In a cell-free system, the nuclear uptake of 5 alpha-[3H]dihydrotestosterone prebound to the cytosol receptor was not inhibited by DMAA. These results suggest that DMAA may inhibit nuclear uptake of 5 alpha-dihydrotestosterone by inhibiting the receptor binding. Sucrose gradient centrifugation of the radioactive KCl nuclear extracts prepared from the tissue incubations showed that the nuclear [3H]testosterone-receptor complex has a greater rate of dissociation than does the nuclear 5 alpha-[3H]dihydrotestosterone-receptor complex. [3H]Testosterone prebound to the prostate cytosol receptor also dissociates faster than 5 alpha-[3H]dihydrotestosterone prebound to the cytosol receptor.
D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase / Q000302:isolation & purification; D058891:5-alpha Reductase Inhibitors; D000818:Animals; D001378:Azasteroids / Q000494:pharmacology*; D001667:Binding, Competitive; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D013196:Dihydrotestosterone / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D007700:Kinetics; D008297:Male; D010088:Oxidoreductases / Q000037:antagonists & inhibitors*; D011467:Prostate / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D011944:Receptors, Androgen / Q000187:drug effects / Q000378:metabolism*; D011987:Receptors, Steroid / Q000378:metabolism*; D013260:Steroids, Heterocyclic / Q000494:pharmacology*
D058891:5-alpha Reductase Inhibitors; D001378:Azasteroids; D011944:Receptors, Androgen; D011987:Receptors, Steroid; D013260:Steroids, Heterocyclic; D013196:Dihydrotestosterone; C031563:17-N,N-diethylcarbamoyl-4-methyl-4-azaandrostane-3-one; D010088:Oxidoreductases; D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase