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4-Hydroxy-4-androstene-3,17-dione (4-OHA) and 4-acetoxy-4-androstene-3,17-dione (4-AcA), in addition to being competitive inhibitors of aromatase, cause time-dependent, irreversible, loss of enzyme activity in both human placental and rat ovarian microsomes. In vivo, treatment of rats with 4-OHA also causes loss of ovarian aromatase activity. To test(More)
The mechanism of inhibition of estrogen synthetase (P-450arom) by 19R- and 19S-isomers of 10-oxiranyl-and 10-thiiranyl-4-estrene-3,17-dione was investigated using human placental microsomes and purified enzyme preparations. The 19R-isomers were potent inhibitors and exhibited affinities 36-fold (10-oxirane) and 80-fold (10-thiirane) greater than the(More)
We have synthesized the (19R)- and (19S)-isomers (2 and 3 respectively) of 10 beta-oxiranylestr-4-ene-3,17-dione. The configurations and conformations of these compounds were established by X-ray crystallographic analysis. Each of these compounds is a powerful competitive inhibitor of human placental microsomal aromatase, and stereoselectivity of inhibition(More)
Human placental aromatase is a cytochrome P-450 enzyme system which converts androgens to estrogens by three successive oxidative reactions. The first two steps have been shown to be hydroxylations at the androgen 19-carbon, but the third step remains unknown. A leading theory for the third step involves ferric peroxide attack on the 19-oxo group to produce(More)
Spontaneous prostatic hyperplasia in the beagle appears to progress with age from a glandular to a cystic histological appearance. Prostatic hyperplasia can be induced in young beagles with intact testes by treatment for 4 mo with either dihydrotestosterone or 5 alpha-androstane-3 alpha, 17 beta-diol, alone, or with either of these steroids in combination(More)
The hypothesis of this study was that broader patterns of physiological channel interactions in the local region of the cochlea are associated with poorer spectral resolution in the same region. Electrically evoked compound action potentials (ECAPs) were measured for three to six probe electrodes per subject to examine the channel interactions in different(More)
Aromatase is a cytochrome P-450 enzyme that catalyzes the conversion of androgens into oestrogens via sequential oxidations at the 19-methyl group. Despite intensive investigation, the mechanism of the third step, conversion of the 19-aldehydes into oestrogens, has remained unsolved. We have previously found that a pre-enolized 19-al derivative undergoes(More)