Danazol inhibits aromatase activity of endometriosis-derived stromal cells by a competitive mechanism

ObjectiveTo evaluate the inhibitory effect of danazol on estrogen (E) production in endometriosis.DesignProspective randomized study.SettingAcademic research unit of the department of obstetrics and gynecology in a university hospital.Patient(s)Thirteen patients with endometriosis.Intervention(s)Danazol was added to the culture of endometriosis-derived stromal cells or suspensions of microsomes prepared from chocolate cysts.Main Outcome Measure(s)The aromatase activities as well as mRNA and protein levels of aromatase in endometriosis-derived stromal cells or microsomes of endometriosis were examined.Result(s)Danazol treatment with a concentration greater than 10−6 M significantly suppressed aromatase activity of endometriosis-derived stromal cells under basal and prostaglandin E2 (PGE2)-stimulated conditions. Danazol (10−5 M) did not affect mRNA and protein levels of aromatase. Danazol competitively inhibited aromatase activity (by 1.7 × 10−6 M of calculated Ki and 2.9 × 10−5 M of Ki′) of endometriosis microsomes.Conclusion(s)Danazol competitively inhibited aromatase activity in endometriosis-derived stromal cells without affecting either the mRNA or protein levels of aromatase. These results indicate the efficacy of local application of danazol to endometriotic lesions.