Histology and histochemistry of the liver of chickens after DENA induced hepatocarcinogenesis and ingestion of low chlorinated biphenyls.

Studies are presented which demonstrate the pathological effects of diethylnitrosamine (DENA) and polychlorinated biphenyls (PCB) in the liver of chickens. DENA, which has been shown to cause tumors in rats and chickens, was tested on 80 laying hens to determine whether changes in the liver during hepatocarcinogenesis were similar to those observed in rats. In addition, the hepatocarcinogenic and cocarcinogenic properties of Clophen C (CC), a technical mixture of low chlorinated biphenyls was tested on chickens. The livers of test animals were examined histologically for preneoplastic and neoplastic lesions. Histochemical methods were used to determine lipid and glycogen contents as well as changes in activity of alkaline phosphatase and gamma-glutamyl-transpeptidase. Putative preneoplastic lesions in the liver were first observed according to the substance and dosage applied as follows: DENA 1 X weekly (group II), beginning on day 258; DENA 2 X weekly (group III), beginning on day 183; and CC + DENA 2 X weekly (group V), beginning on day 231. Application of CC alone did not induce lesions. The concept that CC has cocarcinogenic capability was substantiated by the fact that animals from group V (CC + DENA 2 X weekly) developed twice as many tumors as did animals from group III (DENA 2 X weekly). Additionally, tumors developed earlier in the former group than in the latter.