Involvement of estrogen receptors alpha and beta in the regulation of cervical permeability

Estrogen increases the permeability of cultured human cervical epithelia (G orodeski, GI. Am J Physiol Cell Physiol 275: C888-C899, 1998), and the effe ct is blocked by the estrogen receptor modulators ICI-182780 and tamoxifen. The objective of the study was to determine involvement of estrogen recept or(s) in mediating the effects on permeability. In cultured human cervical epithelial cells estradiol binds to high-affinity, low-capacity sites, in a specific and saturable manner. Scatchard analysis revealed a single class of binding sites with a dissociation constant of 1.3 nhl and binding activi ty of similar to 0.5 pmol/mg DNA. Estradiol increased the density of estrog en-binding sites in a time- and dose-related manner (half time approximate to 4 h, and EC50 approximate to 1 nM). RT-PCR assays revealed the expressio n of mRNA for the estrogen receptor alpha (alpha ER) and estrogen receptor beta (beta ER). Removal of estrogen from the culture medium decreased and t reatment with estrogen increased the expression of alpha ER and beta ER mRN A. In cells not treated with estrogen, ICI-182780 and tamoxifen increased b eta ER mRNA. In cells treated with estrogen, neither ICI-182780 nor tamoxif en had modulated significantly the increase in alpha ER or beta ER mRNA. Th e transcription inhibitor actinomycin D blocked the estrogen-induced increa se in permeability, and it abrogated the estradiol-induced increase in estr ogen binding sites. These results suggest that the estrogen-dependent incre ase in cervical permeability is mediated by an alpha ER-dependent increase in transcription.