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

Abstract

Electrophysiological studies of low-resistance junctions between [rat] Novikoff heptatoma cells grown in suspension cultures were carried out and correlated with gap-junctional areas per interface determined by freeze-fracture. The mean coupling coefficient between isolated cell pairs was 0.773 .+-. 0.025 (SEM, standard error of the mean) in 67G medium and 0.0653 .+-. 0.028 in M67 medium; the respective means for the central pairs of 4 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 .times. 107 .OMEGA. (67G) and 2.01 .+-. 0.01 .times. 107 .OMEGA. (M67), and the respective estimates for specific nonjunctional resistances were 158.6 .+-. 8.1 .OMEGA.-cm2 (67G) and 133.0 .+-. 812 .OMEGA.-cm2 (M67). Mean estimates of junctional conductances were 0.409 .+-. 0.058 .times. 10-6 mho (67G) and 0.211 .+-. 0.018 .times. 10-6 mho (M67) for pairs and 0.291 .+-. 0.063 .times. 10-6 mho (67G) and 0.212 .+-. 0.04 mho (M67) for 4 cell chains. The mean area of gap junction per interface for separate cell populations was 0.187 .+-. 0.049 .mu.m2 and 0.269 .+-. 0.054 .mu.m2 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 .times. 102 mho/cm2 and 0.78 .times. 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.