Effects of black cohosh on estrogen biosynthesis in normal breast tissue in vitro.

[OBJECTIVES] To investigate the effect of black cohosh on the estrogen biosynthesis in the breast in vitro.

[METHODS] Steroid sulfatase (STS) activity was studied in normal breast tissue obtained from pre- and postmenopausal women undergoing reduction mammoplasty. STS protein expression was studied by immunohistochemistry and western blotting. Breast tissue was incubated in vitro without or with black cohosh (iCR) at concentrations ranging from 0.1mg/ml to 1 ng/ml. STS activity was evaluated by incubating homogenized breast tissue with [3H]-estrone sulfate, separating the formed products, estrone (E1) and estradiol (E2), by thin layer chromatography and measuring the amounts of E1 and E2 by scintillation counting.

[RESULTS] STS protein expression and enzymatic activity were detected in all specimens investigated. In all groups, significantly more E1 than E2 was produced. Local estrogen formation was decreased in premenopausal breast tissue by treatment with iCR at 0.1mg/ml (p<or=0.05).

[CONCLUSIONS] iCR decreases local estrogen formation in normal human breast tissue in vitro. This may contribute to the lack of hormonal effects of black cohosh in breast tissue observed in previous studies.