Effect of Cyproterone Acetate on Aromatase Activity in Cultured Human Genital Skin Fibroblasts

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Cyproterone acetate(CA), a well-known competitive antiandrogen, has been used for the treatment of precocious puberty, prostatic adenocarcinoma, hirsutism and hypersexuality. However, there have been some reports of troublesome gynecomastia developing during the use of this drug. It was, therefore, of interest to investigate the effect of CA on peripheral aromatization, since it is the major source of circulating estrogens in men. Our recent studies of aromatase activity in human skin fibroblasts demonstrated that the skin is an important site of extraglandular aromatase activity in men and suggested that these cells might provide a valuable new system in which to study the enzyme. Estrogen formation was assayed by the [3H]H2O technique, after 3h incubation of the cells with androstenedione. The initial experiment was designed to test the effect of CA (10(-8) to 10(-5) M) on baseline aromatase activity during a 12h preincubation in the presence of fetal bovine serum (FBS). Baseline aromatase activity was not affected by the presence of CA, whereas medroxyprogesterone acetate, a similar synthetic progestogen, induced a 2-fold stimulation of aromatase activity at a concentration of 10(-5) M. In cells preincubated with dexamethasone (DEX) in the presence of FBS, aromatase activity was stimulated markedly. When the cells were preincubated in the medium containing FBS with DEX (2.5 X 10(-7) M) in the presence of CA (10(-7) to 10(-4) M), DEX-stimulated levels of aromatase activity were inhibited by CA in a dose-dependent fashion. A competitive binding assay using [3H]DEX, showed that CA was able to compete with DEX for glucocorticoid receptor and the relative binding affinity of CA was approximately 50 times less than DEX. This suggested that the inhibitory effect of CA was due to competition with DEX for receptor binding. Aromatase activity was also stimulated by (Bu)2cAMP (1mM) in the absence of FBS. The stimulatory effect of (Bu)2 cAMP was maximal after 12-24h of preincubation, and this level was maintained for 60h. Similar to the DEX stimulation, stimulation of aromatase activity by (Bu)2cAMP required both RNA and protein synthesis, since the stimulatory effect of (Bu)2cAMP was abolished by co-preincubation with cycloheximide or actinomycin D. When CA was present during either the 12h preincubation or assay incubation, no difference was found in the (Bu)2cAMP-stimulated levels of aromatase activity. On the other hand, the non-aromatizable androgen dihydrotestosterone (DHT) (10(-8) to 10(-6) M) inhibited the stimulation of aromatase activity by (Bu)2cAMP in a dose-dependent fashion.(ABSTRACT TRUNCATED AT 400 WORDS)