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

OBJECTIVE: To evaluate the inhibitory effect of danazol on estrogen (E) production in endometriosis. DESIGN: Prospective randomized study. SETTING: Academic 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 E(2) (PGE(2))-stimulated conditions. Danazol (10(-5) M) did not affect mRNA and protein levels of aromatase. Danazol competitively inhibited aromatase activity (by 1.7 x 10(-6) M of calculated Ki and 2.9 x 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.