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

Abstract

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 +/- 0.32 x 10(7) ohm (67G) and 2.01 +/- 0.01 x 10(7) 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 10(-6) 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 micron 2 and 0.269 +/- 0.054 micron 2 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 10(2) mho/cm2 and 0.78 x 10(2) 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.