Intercellular communication in normal and regenerating rat liver: a quantitative analysis.

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Abstract
Intercellular communication was compared in the regenerating and normal livers of weanling rats. The electrophysiological studies were conducted at the edge of the liver. Here as elsewhere in the liver there is a dramatic decrease in the number and size of gap junctions during regeneration. The area of hepatocyte membrane occupied by gap junctions is reduced 100-fold 29-35 h after hepatectomy. By combining observations made with the scanning electron microscope with the freeze-fracture data, the number of communicating interfaces (areas of contact between hepatocytes that include at least 1 gap junction) formed by hepatocytes was estimated in the normal and regenerating liver. In normal liver a hepatocyte forms gap junctions with every hepatocyte it contacts (.apprx. 6). In regenerating liver a hepatocyte forms detectable gap junctions with, on average, only 1 other hepatocyte. Intercellular spread of fluorescent dye and electric current is reduced in regenerating as compared with normal liver. The incidence of electrical coupling is reduced from 100% of hepatocyte pairs tested in control liver to 92% in regenerating liver. Analysis of the spatial dependence of electrotonic potentials indicates a substantial increase in intercellular resistance in regenerating liver. A quantitative comparison of the morphological and physiological data is complicated by tortuous pattern of current flow and by inhomogeneities in the liver during regeneration. These results are consistent with the hypothesis that gap junctions are aggregates of channels between cell interiors.