Reduction of diethylnitrosamine-induced hepatoma in rats exposed to polychlorinated biphenyls through their dams.

A potent hepatocarcinogen, diethylnitrosamine (DEN), was orally administered at 50 ppm for 5 weeks to Wistar rats preexposed to polychlorinated biphenyls (PCB) in utero and via mother's milk. The numbers of liver tumors induced by administration of DEN were significantly reduced in the rats exposed to PCB in an early stage of life, compared with control rats. This tumor-inhibiting action was particularly clear in male offspring.