Cell-to-cell transfer of EtBr. (A) EtBr flux between a HeLaCx40A96S cell pair. Epifluorescent images taken at 2-, 5-, and 12-min marks after dye injection into the rightmost cell. Bar, 10 µm. Plots of fluorescence intensity versus time for an injected cell (●) and a recipient cell (○) obtained from A96S (B) and G38D (C) mutant pairs. g_j of 20 and 15 nS was measured at the end of dye transfer. Note a significant fluorescence intensity increase delay in the recipient cell (B) caused by intracellular binding. (D) Summary plots of the relative fluorescence intensity versus g_j for EtBr in cells expressing Cx40 mutants: G38D (green circles), A96S (red circles), M163 V (yellow circles), WT hCx40 (white circles), and WT rCx40 (black circles). Solid lines are the first-order regressions.