Gap junctions in 9L and C6 glioma cells: correlation with growth characteristics.

The relationship between growth properties and gap junctional communication properties of two glioma cell lines, 9L and C6, was compared. Using microinjection of a gap junction permeable fluorescent dye, it was demonstrated that 9L cells were extensively dye coupled through gap junctions, whereas C6 cells had low levels of dye coupling between the cells. More gap junctions were observed between 9L cells than between C6 cells both by electron microscopy and immunofluorescent labelling with specific antibodies. Immunoblotting and immunofluorescence labelling of cellular proteins from 9L and C6 cells also showed differences in the Cx43 connexin contents of these cells, reflecting the differences in their gap junctional communication. Northern blot analyses confirmed that the level of Cx43 mRNA was higher in 9L than in C6 cells. In spite of these differences in gap junctions, the two cell lines did not differ in their growth rates in cultures. These results suggest a lack of direct correlation between gap junctional communication and cell growth regulation in these two glioma cell lines.