Estrogen modulates tight junctional resistance (R_TJ) through ER-mediated remodeling of occludin. The objective of the study was to understand the mechanisms involved. Experiments using human normal vaginal-cervical epithelial cells (hEVEC) showed that hEVEC secrete constitutively matrix-metalloproteinase-7 (MMP-7) into the luminal solution, and that MMP-7 is necessary and sufficient to produce estrogen decrease of R_TJ and remodeling of occludin. Treatment with estrogen stimulated activation of the pro-MMP-7 intracellularly and augmented secretion of the activated MMP-7 form. Steady-state levels of MMP-7 mRNA and protein were not affected by estrogen. Estrogen modulated phosphorylation of the MMP-7 but the changes were most likely secondary to changes in cellular MMP-7 mass. Estrogen increased co-immunoreactivity of MMP-7 with the Golgi protein GPP130. Tunicamycin and brefeldin-A had no effect on cellular MMP-7 but monensin (inhibitor of Golgi traffic) blocked estrogen effects, suggesting estrogen site of action is at the Golgi system. Estrogen increased generalized secretory activity, including of luminal exocytosis of polycarbohydrates. However, estrogen increased co-immunoreactivity of MMP-7 with SNAP25 in apical membranes, suggesting SNARE-facilitated exocytosis of MMP-7. Treatment with the V-ATPase inhibitor bafilomycin A₁ inhibited activation of MMP-7. These data suggest that estrogen upregulates activation of the MMP-7 intracellularly, at the level of Golgi, and augments secretion of activated MMP-7 through SNARE-dependent exocytosis. On the other hand estrogen-acidification of the luminal solution would tend to alkalinize exocytotic vesicles, and may lead to decreased activation of the MMP-7. These mechanisms acting in concert could be important for regulation and control of estrogen modulation of paracellular permeability in vivo.