Inhibition of metabolic cooperation in Chinese hamster V79 cells in culture by various polybrominated biphenyl (PBB) congeners.

Using an in vitro assay system to measure a form of cell-cell communication in Chinese hamster V79 cells, several purified polybrominated biphenyl (PBB) congeners were analyzed for their ability to affect colony-forming ability and "metabolic cooperation" in these cells. Results clearly demonstrate the assay's ability to distinguish differences in the cytotoxic and metabolic cooperation-inhibiting properties of these congeners related to their structure. It appears that if a carbon ortho to the bridge carbon of each phenyl ring is brominated, the molecule has the property by which metabolic cooperation is inhibited. The results suggest that several PBB congeners share at least one property associated with several known tumor promoters, such as the phorbol esters. Although we have not ruled out that the mixture of PBB congeners might contain initiators or that various PBB metabolites would be mutagen/initiators, based on these and other results, it was concluded that the reported carcinogenic potential of PBB seems to be mediated by its action as a tumor promoter, rather than as a complete carcinogen or an initiator.