Calcium regulates estrogen increase in permeability of cultured CaSki epithelium by eNOS-dependent mechanism

Estrogen increasesbaseline transepithelial permeability across CaSki cultures andaugments the increase in permeability in response to hypertonicgradients. In estrogen-treated cells, lowering cytosolic calciumabrogated the hypertonicity-induced augmented increase in permeabilityand decreased baseline permeability to a greater degree than inestrogen-deprived cells. Steady-state levels of cytosolic calcium inestrogen-deprived cells were higher than in estrogen-treated cells.Increases in extracellular calcium increased cytosolic calcium more inestrogen-deprived cells than in estrogen-treated cells. However, inestrogen-treated cells, increasing cytosolic calcium was associatedwith greater increases in permeability in response to hypertonicgradients than in estrogen-deprived cells. Lowering cytosolic calciumblocked the estrogen-induced increase in nitric oxide (NO) release andin the in vitro conversion of L-[³H]arginineto L-[³H]citrulline. Treatment with estrogenupregulated mRNA of the NO synthase isoform endothelial nitric oxidesynthase (eNOS). These results indicate that cytosolic calcium mediatesthe responses to estrogen and suggest that the estrogen increase inpermeability and the augmented increase in permeability in response tohypertonicity involve an increase in NO synthesis by upregulation ofthe calcium-dependent eNOS.