Estrogen biphasic regulation of paracellular permeability of cultured human vaginal-cervical epithelia.

The objective of the study was to understand effects of estrogen and aging on paracellular permeability of human vaginal-cervical epithelia. Assays included determinations of transepithelial electrical conductance across cultures of normal human ectocervical epithelial cells on filters. Baseline transepithelial electrical conductance across steroid-deprived cells from postmenopausal women was lower than across cells of premenopausal women. Short-term (24-48 h) treatment with 10 nM 17beta-estradiol increased transepithelial electrical conductance in both groups of cells. In cells of premenopausal women longer-term treatment with estrogen for up to 14 d had no additional effect on permeability, but in cells of postmenopausal women it caused a secondary increase in transepithelial electrical conductance that continued for the duration of the 2-wk treatment. Binding assays of 17beta-[(3)H]estradiol revealed saturable binding to high affinity (1.2-1.3 nM), low capacity sites (0.2-1.2 pmol/mg DNA) in cells of both premenopausal and postmenopausal women. In both types of cells treatment with 17beta-estradiol increased 17beta-[(3)H]estradiol binding activity in a time- and dose-related manner (EC(50) 1 nM; maximal effect within 9-12 h), and increased estrogen receptor-alpha and -beta mRNA. 8-Br-cGMP, a stable cell-permeant analog of cGMP, could mimic the estrogen first phase increase in transepithelial electrical conductance, but not the secondary increase. Treatment with estrogen augmented the increase in transepithelial electrical conductance that was induced by hydrostatic gradients (modulator of the resistance of the lateral intercellular space), and the effect was independent of woman's age or baseline transepithelial electrical conductance. In contrast, the effect of low extracellular calcium (modulator of the tight junctional resistance) was more potent in cells of premenopausal women than in cells of postmenopausal women and was independent of treatment with estrogen. These results suggest that changes in vaginal-cervical epithelial permeability after menopause are determined by aging-related increase in tight junctional resistance, and by low estrogen-dependent increase in lateral intercellular space that lead to net increase in total paracellular resistance and decreased permeability and result in reduced lubrication of the lower genital canal.