Figure 4. High extracellular NaCl induces DNA binding of AP-1 in RPE cells, as indicated by the increased level of the complexes of AP-1 protein and labeled oligonucleotides in electrophoretic mobility shift assay (EMSA; above and middle). Such an increase was not observed under isoosmotic conditions. High NaCl did not induce an increase in the level of the cAMP response element-binding protein (CREB)/oligonucleotide complexes (below). The cells were stimulated with the addition of 100 mM NaCl to the culture medium for 2 and 6 h. Control blots were obtained with nuclear extracts of cells cultured for 6 h. The addition of an excess of unlabeled oligonucleotides (Competitor) was used to show the specificity of the AP-1- and CREB/oligonucleotide complexes. Similar results were obtained in four independent experiments using cells from different donors.