Effect of in vivo exposure to the liver tumor promoters phenobarbital or DDT on the gap junctions of rat hepatocytes: a quantitative freeze-fracture analysis

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Abstract
Some effects of in vivo exposure to the liver tumor promoters phenobarbital (PB) and p,p' -dichlorodiphenyltrichloroethane (DDT) on the gap junctions of hepatocytes were examined in a freeze-fracture analysis, using three groups of male ACI rats. Fifteen animals in Group 1 received a basal diet and were killed sequentially at 0, 2, 4, 6 and 8 weeks (three rats at each point) after the start of the experiment. Groups 2 (12 rats) and 3(12 rats) were given 0.05% PB-and 0.05% DDT containing diets respectively, and were also killed as Group 1. The frequency of hepatocyte gap junctions (per unit total membrane area) was always greater in PB-treated rats than in control rats at each killing point. In rats given DDT, the frequency of hepatocyte gap junctions was greater than in control rats at 2 and 4 weeks but was less than in control rats at 6 and 8 weeks. The average area of hepatocyte gap junctions in PB-and DDT-treated rats was significantly smaller than that in the corresponding control group (Pin vivo exposure to PB or DDT may suggest an inhibitory effect of these agents on intercellular communication.