The estrogen binding activity in the human uterine cervix was measured, and the effect of natural and synthesized steroids on the activities was determined. To assay the estrogen binding activity, the asmple was incubated with 10nM [(3)H] estradiol-17β at 30℃ for 2 hours. Then dextran-coated charcoal (DCC) was added to a final concentration of 0.5% to separate bound/free (B/F) estradiol. Estrogen binding activity was determined by subtracting the activity found in the heated sample from the corresponding activity in the untreated sample. For this purpose it was found appropriate to heat the sample at 40℃ for 60 minutes. The dissociation constant obtained from the Scatchard plot analysis was : kd=2.0×10(-9)M. A variety of steroids at the same molar concentration (1.0 μM) were added to the sample to determine their effects on the estrogen binding activity. For binding with [(3)H] estradiol-17β, the synthetic estrogens were strongly inhibitory, the anti-estrogen agents were strong-ly to moderately inhibitory. Dannazol, which has been used for the treatment of en-dometriosis, was found to be as effective as androgens. All of those inhibitory effects occur-red in a non-competitive manner
