Quantitative analysis of low-resistance junctions between cultured cells and correlation with gap-junctional areas

Electrophysiological studies of low-resistance junctions between Novikoff hepatoma cells grown in suspension cultures were carried out and correlated with gap-junctional areas per inferface determined by freeze-fracture. The mean coupling coefficient between isolated cell pairs was 0.773 ± 0.025 (SEM) in 67G medium and 0.653 ± 0.028 in M67 medium; the respective means for the central pairs of four-cell chains were 0.714 ± 0.034 and 0.595 ± 0.026. Mean estimates of nonjunctional resistances for cell pairs were 3.0 ± 0.32x10⁷ ohm (67G) and 2.01 ± 0.01 X 10⁷ ohm (M67), and the respective estimates for specific nonjunctional resistances were 158.6 ± 8.1 ohm-cm² (67G) and 133.0 ± 812 ohm-cm² (M67). Mean estimates of junctional conductances were 0.409 ± 0.058 X 10-⁶ mho (67G) and 0.211 ± 0.018 X 10-⁶ mho (M67) for pairs and 0.291 ± 0.063 X 10⁶ mho (67G) and 0.212 ± 0.04 mho (M67) for four-cell chains. The mean area of gap junction per interface for separate cell populations was 0.187 ± 0.049 μm² and 0.269 ± 0.054 μm² for cells fixed in loose pellets and in suspension, respectively. When compared with the mean junctional conductance, these values gave specific junctional conductance estimates of 1.13 X 10² mho/cm² and 0.78 X 10² mho/cm², respectively. These values are higher than most previous estimates, but are consistent with the hypothesis that gap-junctional particles contain central hydrophilic channels, about 2 nm in diameter, which have cytoplasmic resistivity.