Rat liver changes after subchronic exposition to polychlorinated biphenyls (PCB) of low chlorine content
Schmoldt, A.; Altenähr, E.; Grote, W.; Dammann, H.G.; Sidau, B.; Benthe, H.F.
Archives of Toxicology 37(3): 203-217
1977
ISSN/ISBN: 0340-5761 PMID: 409375 DOI: 10.1007/bf00355489
Accession: 041174895
Liver changes were studied after subchronic feeding a diet containing 2000 ppm Pcb [chlorine content 42% corresponding to trichlorobiphenyls (tri CB)]. The products differed in their content of highly chlorinated biphenyls (≥Cl5-biphenyl; 5%=tri CB-5, 2%=tri CB-2 and 0.4%=tri CB-0.4). The most striking difference was observed in respect to their porphyrinogenic actions. Tri CB-0.4 and tri CB-2 caused an increase of porphyrins about 10-fold, whereas the liver porphyrin content of tri CB-5 treated rats was 175-fold higher than normal. In all cases of porphyria the porphyrins consisted mainly of uro- and heptacarboxyporphyrin. In contrast to their different porphyrinogenic effects all tri Cb products caused an equal induction of δ-aminolaevulinate synthetase, but no increase of δ-aminolaevulinate dehydratase activity. Tri CB-5 was also a stronger inducer than tri CB-0.4 and tri CB-2 regarding microsomal monoxygenases and UDP-glucuronyltransferase. The quantitative differences of the effect can be correlated to Pcb residues in the liver. In tri CB-5 fed rats a much higher accumulation of highly chlorinated components could be determined. The histological examination by light and electron microscopy showed no significant differences in the effects caused by all three tri Cb products. In livers of all rats cell hypertrophy could be observed due to a considerable hyperproliferation of tubular and vesicular SER. Ser membranes were tightly packed and sometimes disrupted. Membrane arrays of various size were found in most hepatocytes. The mitochondria were dislocated by these formations and were sometimes swollen. There was neither centrilobular or periportal necrosis nor fibrosis nor fatty degeneration. It may be concluded that Pcb of low chlorine content (42%) are much less toxic than highly chlorinated PCB. However, the small amount of highly chlorinated components, present as contaminants in commercial products containing 42% chlorine, may accumulate and exert toxic effects.