Effects of chemically pure chlorobiphenyls on the morphology of rat liver

Abstract

Pure biphenyl and a series of isomerically pure mono-, di-, tetra-, hexa- and octa-chlorobiphenyls of known chemical composition were injected ip (50 mg/kg) into young male Wistar rats for 3 consecutive days and the rats were killed 4 days after the last injection. In a second experiment, rats were injected ip with 4-mono, 4,4′-di- and 2,5,2′,5′-tetrachlorobiphenyl (100 mg/kg) for 7 days. The effects of the pure PCBs were compared with those caused by o,p′- and p,p′-DDT and Aroclor 1254 and 1260. Samples of liver were examined by light and electron microscopy. The major alterations observed within the hepatocytes were marked proliferation of smooth endoplasmic reticulum and increased numbers of microbodies and lipid droplets. Biphenyl and 2,2′-dichlorobiphenyl produced few morphologic effects whereas 4,4′-di-, 2,5,2′,5′- and 3,4,3′,4′-tetrachlorobiphenyl caused more changes. The highly chlorinated hexa- and octachlorobiphenyls produced morphological changes that were comparable to those produced by DDT, and Aroclors 1254 and 1260. The degree of ultrastructural alteration appeared to be related directly to the number of chlorine atoms and the presence of chlorine in the 4- or 4′-position.