An improved long-term culture of rat hepatocytes to detect liver tumour-promoting agents: results with phenobarbital.

Among various cocultures of hepatocytes with other cell types, we found that mouse embryonal cells (BALB/c 3T3) are more effective in maintaining rat hepatocytes in vitro. Because most human cancers are epithelial in origin, we thought that such a hepatocyte culture system could be used for the detection of tumour-promoting agents, most of which are inhibitors of gap-junctional intercellular communication. We, therefore, have examined the effect of the strong rat liver tumour promoter, phenobarbital, on the gap-junctional intercellular communication capacity of hepatocytes in long-term cultures. A single application of phenobarbital drastically inhibited the gap-junctional intercellular communication between hepatocytes in a coculture for only several hours, but treatment for 3 weeks provoked a constant decrease of gap-junctional intercellular communication (50%) throughout the treatment period. This type of long-term culture of rat hepatocytes may be usable in a rapid in vitro assay to detect tumour-promoting agents.