Chatterton Robert T, Geiger Angela S, Gann Peter H, Khan Seema A
Department of Obstetrics and Gynecology, Feinberg School of Medicine of Northwestern University, 710 N Fairbanks Court, Chicago, IL 60611, USA.
J Steroid Biochem Mol Biol. 2003 Aug;86(2):159-66. doi: 10.1016/s0960-0760(03)00266-8.
The study was designed to determine the process and limitations by which estrone sulfate may be a precursor of estradiol in the parenchymal cells of the normal breast. The concentration of estrone sulfate in breast nipple aspirate fluid was 1000-fold greater than that of estradiol. Concentrations of 3H-estrone sulfate in parenchymal cells were only 0.20-0.33 times that of the 1.0 nM concentration in the medium, while 3H-estrone achieved concentrations up to 24 times that in the medium at 37 degrees C. Nevertheless, estrone sulfate added to the medium was linearly converted within a 1000-fold concentration range to estrone in intact cells with a mean half-time of conversion of 628 min per 10(6) cells. Homogenized cells had a half-time of 246 min per 10(6) cells. Thus, the time for entry of estrone sulfate into cells reduced the rate by approximately 55%. In split samples, the Vmax values (+/- S.D.) for intact and homogenized cells were 12.6 +/- 1.4 and 18.3 nmol/h mg DNA, respectively (P<0.03). The corresponding Km values for intact and homogenized cells were 6.0 +/- 1.1 and 4.7 +/- 1.0 microM. Conversion of estrone sulfate to estradiol was more efficient in intact cells than in homogenates with mean half-times of 2173 and 7485 min per 10(6) cells, respectively. Conversion of estrone to estrone sulfate did not occur in these cells despite sulfonation of estrone by MCF-7 breast cancer cells under identical conditions. It is concluded that estrone sulfate can serve as a precursor for estradiol in normal breast tissue. Conversion of estrone to estradiol is a limiting step in the process.
本研究旨在确定硫酸雌酮在正常乳腺实质细胞中作为雌二醇前体的过程及局限性。乳腺乳头抽吸液中硫酸雌酮的浓度比雌二醇高1000倍。实质细胞中3H-硫酸雌酮的浓度仅为培养基中1.0 nM浓度的0.20 - 0.33倍，而在37℃时，3H-雌酮的浓度达到培养基中浓度的24倍。然而，添加到培养基中的硫酸雌酮在完整细胞中在1000倍浓度范围内呈线性转化为雌酮，每10⁶个细胞的平均转化半衰期为628分钟。匀浆细胞每10⁶个细胞的半衰期为246分钟。因此，硫酸雌酮进入细胞的时间使速率降低了约55%。在分割样本中，完整细胞和匀浆细胞的Vmax值（±标准差）分别为12.6 ± 1.4和18.3 nmol/h mg DNA（P<0.03）。完整细胞和匀浆细胞的相应Km值分别为6.0 ± 1.1和4.7 ± 1.0 μM。硫酸雌酮转化为雌二醇在完整细胞中比在匀浆中更有效，每10⁶个细胞的平均半衰期分别为2173和7485分钟。尽管在相同条件下MCF - 7乳腺癌细胞能使雌酮硫酸化，但这些细胞中未发生雌酮转化为硫酸雌酮的过程。结论是硫酸雌酮可作为正常乳腺组织中雌二醇的前体。雌酮转化为雌二醇是该过程中的限速步骤。
