Estrogenic and antiestrogenic effects of danazol administration in studies of estradiol receptor binding.

In order to study possible cellular estrogenic and/or antiestrogenic effects of danazol, immature female rats were treated with danazol (10 mg/kg/day) or propylene glycol (control) for 4 days (short-term study) and 14 days (long-term study). Estradiol receptor-binding assays were done on the cytosol fraction of the homogenized uterine tissue of each group. AT saturation levels of substrate, short-term danazol treatment was uterotropic and induced an increase in estradiol receptor concentration and binding (p less than 0.02). Long-term treatment, however, caused a marked decrease in estradiol receptor capacity (p less than 0.001). This disparity of the effect of danazol on estradiol receptors suggests a dose- or duration-dependent mechanism of action in the target tissue that may account for some of the clinical effects seen in patients receiving this drug.