FIGURE 6.

Bipolar electroporation loading and dye transfer via gap junctions in C6 glioma cells. (A) Size of the 6-CF-loaded cell zone in WT and connexin-transfected C6 cells, 30 min after electroporation. The size of the loaded zone in C6-WT was not different from that in ECV304, as can be appreciated by comparison with Fig. 4 B. In C6-Cx43 and C6-Cx32, the loaded zone was significantly larger than that in C6-WT. Electroporation loading with the gap-junction-impermeable dyes 3 or 10 kDa dextran fluorescein (DF) resulted in very small zones, because the efficiency of loading these high-molecular-weight probes into the cells was much lower than that for 6-CF (see Fig. 4 A). (B) Example traces of the fluorescence intensity profile for the conditions indicated, 30 min after electroporation. The fluorescence intensity in the ordinate was normalized to the peak of the intensity profile, and each curve is the average of eight different experiments. The image on top of the graph illustrates a representative example of 6-CF loading in C6-WT. (C) Averaged data for the standard deviation of dye spread σ as determined by fitting individual intensity profiles to a Gauss equation. The σ of 6-CF spread was significantly larger in C6-Cx43 and C6-Cx32 than in C6-WT. Carbenoxolone (CBX) treatment (25 μM, 30 min) significantly reduced σ, and an even lower σ was observed when the cells (C6-Cx32) were loaded with the gap-junction-impermeable 3- or 10-kDa dextran fluoresceins. Stars give significances as compared with C6-WT; n = 8 for A and C.