direct competition experiments performed with intact cells in monolayer culture showed that , under conditions of minimal metabolism , only delta 5-diol could significantly compete with estradiol for cellular estrogen-specific binding sites with an apparent dissociation constant of 11 nm , thus suggesting that physiological concentrations of c19-delta 5-steroids of adrenal origin could exert an estrogenic stimulation of breast tumor growth without involvement of the aromatase pathway .
C0014939
estrogen
C1458155
breast