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

Estrogen increases baseline transepithelial permeability across CaSki cultu res and augments the increase in permeability in response to hypertonic gra dients. In estrogen-treated cells, lowering cytosolic calcium abrogated the hypertonicity-induced augmented increase in permeability and decreased bas eline permeability to a greater degree than in estrogen-deprived cells. Ste ady-state levels of cytosolic calcium in estrogen-deprived cells were highe r than in estrogen-treated cells. Increases in extracellular calcium increa sed cytosolic calcium more in estrogen-deprived cells than in estrogen-trea ted cells. However, in estrogen-treated cells, increasing cytosolic calcium was associated with greater increases in permeability in response to hyper tonic gradients than in estrogen-deprived cells. Lowering cytosolic calcium blocked the estrogen-induced increase in nitric oxide (NO) release and in the in vitro conversion of L-[H-3] arginine to L-[H-3] citrulline. Treatmen t with estrogen upregulated mRNA of the NO synthase isoform endothelial nit ric oxide synthase (eNOS). These results indicate that cytosolic calcium me diates the responses to estrogen and suggest that the estrogen increase in permeability and the augmented increase in permeability in response to hype rtonicity involve an increase in NO synthesis by upregulation of the calciu m-dependent eNOS.