Specific estrogen binding proteins in human cervix

Abstract

An estrogen binding protein has been found in all regions of the human cervix. The greatest concentration per mg protein was associated with the region including the columnar epithelium, less associated with the squamous epithelium, and an intermediate concentration in the remaining stroma. These concentrations were 5–10-fold lower than those found in the corresponding uterine tissue, but the association constants were similar (0.9–2.6 nM −1). The dissociation rate constant was found to be 0.74 × 10 −6 s −1 at 0° and a sedimentation coefficient of 4.2–4.8S plus aggregates was observed. The binding was highly specific for estrogens (estradiol > estrone > estriol) but was unaffected by progesterone, testosterone, or cortisol in the nM range. Synthetic estrogens were also potent competitors (ethinyl-estradiol > estradiol > diethylstilbestrol > mestranol). Uterine estrogen binding sites were significantly higher in the proliferative phase of the menstrual cycle than in the secretory phase, expressed either per g wet weight or per mg protein ( P <0.01). Cervical estrogen binding sites were significantly higher in the proliferative phase when expressed per g wet weight ( P < 0.05) but not per mg protein. It is concluded that human cervix contains estrogen binding proteins with properties similar to those found in the corpus. The data collected so far suggest that levels of this binding activity may fluctuate in cervix in a manner similar to that found in endometrium.